Non-motoring > Amp overheating again - how much for repair?	Miscellaneous
Thread Author: RattleandSmoke	Replies: 124

Thu 25 Nov 10 23:14   Amp overheating again - how much for repair? - RattleandSmoke

I am going to drop my amp off tomorrow as it keeps over heating. I don't think it is a thermal paste problem as it gets so hot you could cook a chicken on it. Any idea what could be causing it? It is a Cambridge 640A so would cost about £150 used of ebay so it is prob worth spending £50-£60 on a repair. I am currently using the headphone output on my old Rotel pre amp but really need to get my amp fixed. I do listen to loud rock music on a saturday night before I go out but its only on the 10 O'Clock position max. The amp also gets very hot and cuts out even if I am just watching TV using my Grado SR60s. If it was a poor bonding between the heat rail and the a transister the actual amp would not be that hot would it? Reply to this message | Report message

Thu 25 Nov 10 23:58   Amp overheating again - how much for repair? - Fenlander

Sorry Rattle but the problem is just the same as you experienced earlier this year... these amps are very prone to overheating with speaker/headphone loads that wouldn't trouble most others. Sell it and get something without these issues. Reply to this message | Report message

Fri 26 Nov 10 00:13   Amp overheating again - how much for repair? - RattleandSmoke

Indeed it is, but I moved the amp to the top of the HIFI rack and it seemed to cure it. Actually selling it might not be a bad idea. I can get £120 for it and then find another £130 I can get a good used amp for £250ish or less. Reply to this message | Report message

Fri 26 Nov 10 00:17   Amp overheating again - how much for repair? - rtj70

I must be missing something in this... but why use this amp to drive headphones? Is that not a problem? For headphone use is something more appropriate not the solution? An amp able to drive speakers then being used for headphones. I am sure I am about to learn something useful.... and there's me thinking of getting a Pure Chronos CD/DAB solution for the kitchen because it fits in the space I want it. Reply to this message | Report message

Fri 26 Nov 10 08:04   Amp overheating again - how much for repair? - Fenlander

Yes you can get specific headphone amps but only so the industry can sell £10 worth of bits in a small box for £250! Over the last 40yrs of h-fi ownership and countless amps I've never had one that wouldn't drive headphones... nor one that overheated. *For total reporting accuracy I should say that doesn't include my current main amp which I've been happy with for over 20yrs... no headphone socket. Reply to this message | Report message

Fri 26 Nov 10 09:23   Amp overheating again - how much for repair? - Old Sock

Is it one of those amps with a volume knob setting of "11"? Reply to this message | Report message

Fri 26 Nov 10 09:36   Amp overheating again - how much for repair? - Iffy

...Over the last 40yrs of h-fi ownership and countless amps I've never had one that wouldn't drive headphones... nor one that overheated... Same here. If I had any piece of audio equipment which was getting hot enough to fry an egg on, I wouldn't be using it. I wouldn't even be leaving it plugged in. Reply to this message | Report message

Fri 26 Nov 10 10:09   Amp overheating again - how much for repair? - Bellboy

me neither i would rather get my old rotel ra611 out rather than live in a hotel while the insurers argue about a house rebuild Reply to this message | Report message

Fri 26 Nov 10 10:35   Amp overheating again - how much for repair? - Iffy

...would rather get my old rotel ra611 out... Probably performs as well as a modern budget amp. Reply to this message | Report message

Fri 26 Nov 10 10:37   Amp overheating again - how much for repair? - Fenlander

Indeed... rather a lot of the emperor's new clothes about the hi-fi market. Reply to this message | Report message

Fri 26 Nov 10 10:41   Amp overheating again - how much for repair? - Bellboy

old stuff has real transformers for starters my modern amp i use for surround keeps losing hf and it wasnt cheap,apparently its a first sign of the capaciters breaking down guess what i had this with my pvr last year so modern stuff is proper carp even my sony digi box only lasted a year and a day and that was the most expensive one on the market when i bought it you cant beat good ole valves and real wiring in a solid steel chassis Reply to this message | Report message

Fri 26 Nov 10 10:48   Amp overheating again - how much for repair? - Zero

Valves never went then? Hand soldered joints never went dry? Wet or waxed capacitors never dried out? I have restored old valve units. Sorry me old fruit, this is a case of "every summer was always hot till xxx years ago" dreamworld. Reply to this message | Report message

Fri 26 Nov 10 10:56   Amp overheating again - how much for repair? - Iffy

The transistorised Japanese hi-fi of the 1970s was generally reliable. Rotel, Trio, Pioneer, Yamaha, Suzuki - OK, not Suzuki, but you get the idea. Reply to this message | Report message

Fri 26 Nov 10 11:05   Amp overheating again - how much for repair? - R.P.

My last two Rotel amps failed - Bought a nicely made Japanese Teac - reliable, good sound runs cool as well. Reply to this message | Report message

Fri 26 Nov 10 11:15   Amp overheating again - how much for repair? - Zero

Rattle Amp = bin Reply to this message | Report message

Fri 26 Nov 10 11:20   Amp overheating again - how much for repair? - Old Sock

>> Rattle >> >> Amp = bin And he doesn't mean 'buy-it-now' :-) Mind you, in the 'audiophile' market, a fool and his money...... Last edited by: Old Sock on Fri 26 Nov 10 at 11:20 Reply to this message | Report message

Fri 26 Nov 10 11:38   Amp overheating again - how much for repair? - RattleandSmoke

I am not sure how old it is, but if I find the receipt I wonder if I could argue it was not fit for purpose? Mind I think it was 2007 when I bought it but it may have been 2008. I am worried if I take it a repair shop they won't be able to properly repair it. I have had a look on ebay but everything is very expensive even the old generic jap amps are going for a lot. I really wish I had kept my old Marantz PM6000 repaired now, I sold it for £50 as it needed a new pot. Reply to this message | Report message

Fri 26 Nov 10 12:22   Amp overheating again - how much for repair? - Fenlander

My worry about the repair is that these amps are known for this so a one-off fix is unlikely to resolve an underlying issues the makers hadn't sorted. There is a world of great 80s/90s amps on ebay for £50-£200 if you latch onto a good deal with one that isn't prone to overheating. Reply to this message | Report message

Fri 26 Nov 10 13:38   Amp overheating again - how much for repair? - Bellboy

ive waited 18 months now for my favourite amp to appear on ebay so i can buy it yes its a mid 70's jap one and thats all im saying.............................. to zero, yes things broke down but in all honesty if you left a valved amp or even reel to reel tape recorder in ideal conditions ie in a fairly moderated heated room you very rarely had dry joints of failling valves,especialy if the valves were genuine rather than say these modern ish cossack copies did i mention i have one of the first reel to reels somewhere in the cellar probably now going green? used to collect them but they take up so much space Reply to this message | Report message

Fri 26 Nov 10 14:28   Amp overheating again - how much for repair? - R.P.

I've got an 80s working Technics amp and Graphic Equaliser in the attic if someone was interested.. Last edited by: Pugugly on Fri 26 Nov 10 at 14:29 Reply to this message | Report message

Fri 26 Nov 10 14:39   Amp overheating again - how much for repair? - Mike Hannon

Nice to see Cambridge is keeping up the old tradition... I have an attic full of Quad stuff, including original electrostatics, that I can't use because I don't have a suitable room. My everyday amp is a circa-1980 Aiwa receiver. Lovely. Whoever said that in the world of the audiophile a fool and his money are soon parted was right. It certainly took enough out of me when I was young and foolish. Incidentally, when I asked the Somerset Quad expert - years ago - if he would change the big electrolytics in my 303 power amp because they were starting to drip, he said 'why don't you just turn it upside down?'. I got them changed anyway... Reply to this message | Report message

Fri 26 Nov 10 14:41   Amp overheating again - how much for repair? - Hard Cheese

I am still using a excellent Yamaha amp cira 1990 and a couple of early '90's Technics CD players that use Philips componentry that was, and still is, well rated. These together with the Mordaunt Short speakers provide a very good sound. However I could easily catch the virrulent new-hifi bug right now ... ... Last edited by: Cheddar on Fri 26 Nov 10 at 14:42 Reply to this message | Report message

Fri 26 Nov 10 14:43   Amp overheating again - how much for repair? - R.P.

Don't Cheddar, I think I may have a 90s Technics MASH CD deck somewhere. Reply to this message | Report message

Fri 26 Nov 10 14:48   Amp overheating again - how much for repair? - Iffy

Some of the early CD decks did have a very metallic sound. The Philips ones were the first budget decks to be regarded as sounding musical. Reply to this message | Report message

Fri 26 Nov 10 14:55   Amp overheating again - how much for repair? - Bellboy

can you get a cd player thats musical? i still havent heard one was on spotify the other night and an LP now unobtainable in this country and i specially imported from america was on their playlist drat however still not as good as a neegle on da record though Reply to this message | Report message

Fri 26 Nov 10 14:58   Amp overheating again - how much for repair? - Iffy

...can you get a cd player thats musical?... Arguably not, but some players are much less harsh and artificial-sounding than others. Last edited by: Iffy on Fri 26 Nov 10 at 14:59 Reply to this message | Report message

Fri 26 Nov 10 15:00   Amp overheating again - how much for repair? - Old Navy

Put it on an extension lead and stick it in the freezer when you want to use it. Reply to this message | Report message

Fri 26 Nov 10 14:59   Amp overheating again - how much for repair? - Hard Cheese

>> Don't Cheddar, I think I may have a 90s Technics MASH CD deck somewhere. >> Seriously PU, dig it out and let me know the model number? Reply to this message | Report message

Fri 26 Nov 10 15:44   Amp overheating again - how much for repair? - R.P.

Technics SL-PS670A Reply to this message | Report message

Fri 26 Nov 10 15:48   Amp overheating again - how much for repair? - Iffy

...Technics SL-PS670A... Just out of interest, has it got any marketing or other messages written on the front? I recall things such as 'mos fet' or 'PLL', which might be phase locked loop. Yamaha used to call their stuff 'natural sound'. Reply to this message | Report message

Fri 26 Nov 10 15:49   Amp overheating again - how much for repair? - R.P.

MASH (I may go up again to look if motivated - did well to remember which box it was in !) Reply to this message | Report message

Fri 26 Nov 10 15:51   Amp overheating again - how much for repair? - R.P.

cgi.ebay.ie/TECHNICS-SL-PS670A-DIGITAL-OUTPUT-CD-PLAYER-REMOTE-EX-/330493056094 Identical to this one Iffy. Reply to this message | Report message

Fri 26 Nov 10 15:55   Amp overheating again - how much for repair? - spamcan61

Cor, didn't realise that stuff was still going for reasonable money. Reply to this message | Report message

Fri 26 Nov 10 16:19   Amp overheating again - how much for repair? - Tooslow

It isn't. Not when I sold a Technics amp / CD player / tuner anyway. Any bargains on eBay are what I'm selling :-( John Reply to this message | Report message

Fri 26 Nov 10 15:56   Amp overheating again - how much for repair? - Iffy

...MASH... Multi-stage noise shaping, I think you'll find. Reply to this message | Report message

Fri 26 Nov 10 16:00   Amp overheating again - how much for repair? - R.P.

Oh. Reply to this message | Report message

Fri 26 Nov 10 16:07   Amp overheating again - how much for repair? - Iffy

...Oh... The cynic in me tells me MASH is meaningless marketing speak, but someone might be along in a minute who knows otherwise. Reply to this message | Report message

Fri 26 Nov 10 16:11   Amp overheating again - how much for repair? - spamcan61

>> ...Oh... >> >> The cynic in me tells me MASH is meaningless marketing speak, but someone might be >> along in a minute who knows otherwise. >> Just the usual junk science marketing rubbish that has infested HiFi for the last 30 years at least. Reply to this message | Report message

Fri 26 Nov 10 16:16   Amp overheating again - how much for repair? - R.P.

The Japanese were very fond of this acronym nonsense on cars and bikes and other consumer stuff at one time - eve my very recent VFR was emblazoned with VTEC ABS....pointless. Reply to this message | Report message

Fri 26 Nov 10 16:26   Amp overheating again - how much for repair? - Hard Cheese

>> Technics SL-PS670A >> Wanna sell it PU? Reply to this message | Report message

Fri 26 Nov 10 16:29   Amp overheating again - how much for repair? - R.P.

Yes - Now I remembered I had it - may as well - I need the space - offers ? Drop me an e-mail.. Last edited by: Pugugly on Fri 26 Nov 10 at 16:35 Reply to this message | Report message

Fri 26 Nov 10 17:06   Amp overheating again - how much for repair? - Fenlander

>>>...Technics SL-PS670A... A very competent player. I had one as a source in a PA system. Sold one on ebay... went all the way to the Western Isles. On true blind testing it can be very hard to tell these mid-range CD players apart.... far away from the chalk & cheese opinions of many magazine tests.... still they have to write something. Last edited by: Fenlander on Fri 26 Nov 10 at 17:11 Reply to this message | Report message

Fri 26 Nov 10 17:57   Amp overheating again - how much for repair? - Hard Cheese

>> Drop me an e-mail.. >> Not sure I have you C4P address, can you mail me perhaps? Is it mint? Reply to this message | Report message

Fri 26 Nov 10 17:59   Amp overheating again - how much for repair? - R.P.

It's used - not sure without digging it out properly - I'll e-mail you some photos afterwards. e-mail in the profile; hondadriver_mod at car4play.com Last edited by: Pugugly on Fri 26 Nov 10 at 18:11 Reply to this message | Report message

Fri 26 Nov 10 18:03   Amp overheating again - how much for repair? - Zero

Dont sell it to him, he'l just moan it has a funny noise. Reply to this message | Report message

Fri 26 Nov 10 18:08   Amp overheating again - how much for repair? - Tooslow

Oops. You published an email address. Bots. Can you edit it pdq? At least break it in two and put "at" in the middle. John Reply to this message | Report message

Fri 26 Nov 10 18:11   Amp overheating again - how much for repair? - R.P.

Thanks John Reply to this message | Report message

Sat 27 Nov 10 08:13   Amp overheating again - how much for repair? - Hard Cheese

>> It's used - not sure without digging it out properly - I'll e-mail you some photos afterwards. >> Many thanks PU! Reply to this message | Report message

Fri 26 Nov 10 19:38   Amp overheating again - how much for repair? - Runfer D'Hills

>> Is it mint? Cheddar, I reckon you could get him to bundle in a bike rack with the deal you know. However, you'd need a towbar for his. Alternatively, you could go for the more convenient clip on style which would be ideal for your BMW, your Focus or indeed for the GTi you were looking at.... If you would like to know where a good deal on such a rare thing could be found feel free to contact me too. ( touches side of nose and winks )... :-) Reply to this message | Report message

Fri 26 Nov 10 20:47   Amp overheating again - how much for repair? - R.P.

E-mails sent - I wasn't convinced that the "work" e-mail was working with attachments so I've sent it from my personal Hotmail account titled "Technics" check your spam Reply to this message | Report message

Fri 26 Nov 10 17:21   Amp overheating again - how much for repair? - Manatee

>>I've got an 80s working Technics amp and Graphic Equaliser in the attic if someone was interested.. Ditto. I'll see what it is tonight, maybe it's what BB's after! I also have a Technics SUA 900 Mk2 in current use - these are great integrated amps, fairly powerful with a very smooth valvey sound, they're now making good money on ebay. Barely gets warm! Reply to this message | Report message

Fri 26 Nov 10 18:38   Amp overheating again - how much for repair? - RattleandSmoke

Paid all my bills for this month, paid some money into my ISA so I have enough to my income tax bill. That means I actually have a bit of spare dough. A mate suggested I find a HIFI shope that does 0% credit and see if I could get something for the £500 region. I just don't know what to do but what ever I buy as to be as good or better than my 650A. I have Wharfdale Diamond 9.1 speakers (not to be confused with older Wharfdale stuff, these are proper speakers) they are very musical but lack a little little, so a slightly brighter amp may suit. The obvious choice would be a used Audio Lab 800A but they may be a bit too bright for my tastes. I have seen a Musical Fedalility A1 amp for £250 on ebay. If I sold my amp I suppose I would have to mention the fact it is a fire starter. Reply to this message | Report message

Fri 26 Nov 10 18:44   Amp overheating again - how much for repair? - R.P.

Sounds like a fake that Rattle ! Reply to this message | Report message

Fri 26 Nov 10 18:54   Amp overheating again - how much for repair? - rtj70

Rattle, don't get into debt (0% or otherwise) to buy an amp. If you cannot afford it this month get it next month. Reply to this message | Report message

Fri 26 Nov 10 19:02   Amp overheating again - how much for repair? - spamcan61

Winter coming on you'll be glad of the heat. Reply to this message | Report message

Fri 26 Nov 10 19:04   Amp overheating again - how much for repair? - RattleandSmoke

Fake HIFI what next? Rob yep you are right especialy as I have been having a bit of cash flow issues lately. I will put some monthly payments into my ISA and get a new amp when I can afford it. Now my parents have a Marantz PM4000 my old amp from donkers years ago, I might ask if I can borrow it while I save up for something better. I have always liked the Marantz sound, I used to have a PM6000 and really angry I sold it for £35 because it kept cutting out on one channel. I do have a mid 90's Rotel Pre amp somebody sold me for £15 and I use that for my phonto stage, so I could even buy a power amp rather than an intergrated. Meanwhile I see Richer sounds have an old Tangent Amp which is made by Eltax, I had one before as a stop gap it has a very boxy transister sort of sound but they are selling them for £20 open box so I may buy one for my parents while I borrow their marantz. I just cannot believe the bad luck I have been having with amps. Reply to this message | Report message

Fri 26 Nov 10 19:04   Amp overheating again - how much for repair? - Old Sock

>> >> If I sold my amp I suppose I would have to mention the fact it >> is a fire starter. Sell it to a Prodigy fan? Reply to this message | Report message

Fri 26 Nov 10 19:06   Amp overheating again - how much for repair? - RattleandSmoke

I thought about that :p. I see Rega are doing amps in the £250 range, I wonder if they will be any good. I want something that will last too. I see is time to visit the old HIFI forum but I have actually got far more replies on here than i would have done on there because it is a dead forum now. Reply to this message | Report message

Fri 26 Nov 10 19:08   Amp overheating again - how much for repair? - rtj70

>> Now my parents have a Marantz PM4000 my old amp from donkers years ago Sounds like a plan. I bet they could get buy on a cheap amp anyway. I was in Microdirect earlier (they have reconditioned Pure Chronos players for around £44) and the chap I know there said this year for them had been quiet. Reply to this message | Report message

Fri 26 Nov 10 19:31   Amp overheating again - how much for repair? - RattleandSmoke

I think its me propping that place up. I must have spent close to £1k in there this month. I tend to go to Heaton Chapel one as there is no returns so it is a lot quicker to be served. I think I am slightly down on last years takings but been steady enough. Reply to this message | Report message

Fri 26 Nov 10 19:52   Amp overheating again - how much for repair? - rtj70

There is a returns counter at the Heaton Chapel Microdirect site. If you should need it. It's a separate queue. Knowing roughly how many work there, I don't think £1000 would go that far. Someone (staff) brought in some pizzas for lunch. About a dozen pizzas were taken in when I was there. :-) Hope things pick up for all though! Reply to this message | Report message

Fri 26 Nov 10 19:59   Amp overheating again - how much for repair? - RattleandSmoke

They moved the returns back to Upper Brook street a few weeks back but they do still take returns but seen lots of arguments in there about it. I know £1K is nothing but that must still be a bit of extra profit for them. I certainly don't need to tell them my account number any more as most the staff know it by now. I really don't want them to go under as I would be stuffed without them. I really don't like using mail order as it is expensive and unreliable. Reply to this message | Report message

Fri 26 Nov 10 19:30   Amp overheating again - how much for repair? - Manatee

>>Ditto. I'll see what it is tonight, maybe it's what BB's after! It's a SU-Z400, 55W / channel I think. I acquired it a while ago to stop somebody binning it - I am saving it for when my son leaves and I can turn his bedroom into my den, but he seems to have taken root. Reply to this message | Report message

Fri 26 Nov 10 20:10   Amp overheating again - how much for repair? - Bellboy

the amp im aiming for is an au but thanks for the kind thought Reply to this message | Report message

Fri 26 Nov 10 20:15   Amp overheating again - how much for repair? - RattleandSmoke

Seen a PM6010 KI on ebay for £150 second hand, at that money it is very tempting. I remember when those were £400+ new. Using the PM4000 at the moment, the sound is not offensive but I can tell everything is rounded off as its power supply cannot cope with even the guns and roses. Reply to this message | Report message

Fri 26 Nov 10 20:20   Amp overheating again - how much for repair? - bathtub tom

I'm glad I'm old, I'll never realise how naff my old audio stuff is. If I ever get my ears syringed it could cost me a small fortune. ;>) Reply to this message | Report message

Fri 26 Nov 10 20:42   Amp overheating again - how much for repair? - jamesh764

At work we have the old model Linn Majik IP amplifier in our office. It's 13 years old and has never broken down. It had accidentally been left playing since Wednesday morning, and when I switched it off this morning the top of the case was still cool. It's got a built in phono stage, and a built in headphone amp. Even though it is an integrated amp you can use the pre and power stages separately. Unlike most other amps from its era it has solid state switching, so there are no switches/potentiometers to crackle. The looks are an acqured taste, it is only 33 watts per channel, and it has stupid speaker connectors, but it sounds excellent. There's one on eBay at the moment for £140. Reply to this message | Report message

Fri 26 Nov 10 20:46   Amp overheating again - how much for repair? - RattleandSmoke

A Linn for £140 sounds too good to be true :). Using my old PM4000 now and its just luke worm, shows there must be a fault with the Cambridge. Reply to this message | Report message

Fri 26 Nov 10 21:02   Amp overheating again - how much for repair? - Iffy

Linn made a bit of news a few months ago when they announced they would no longer be making CD players. Industry watchers say where a high-end maker leads, mainstream makers will inevitably follow. The future of the CD is not bright. Last edited by: Iffy on Fri 26 Nov 10 at 21:05 Reply to this message | Report message

Fri 26 Nov 10 21:11   Amp overheating again - how much for repair? - RattleandSmoke

I predicted that a long time ago anyway. Vinyl will always have a place because it can sound brilliant, the problem with CDs is files stored on a hard drive can sound just as good so it means CD no longer as the sound quality or convience advantage. I still enjoy getting my final out on ocassions. Reply to this message | Report message

Fri 26 Nov 10 21:01   Amp overheating again - how much for repair? - RichardW

Pugugly wrote: "Bought a nicely made Japanese Teac - reliable, good sound runs cool as well. " We've got a TEAC Reference 300 set. Had it nearly 12 years, sounds brilliant and it never overheats! Looks timeless (to me anyway!) and has a real solid feel about it. Always highly rated in tests for quote a few years it was available new. Decent price on e-bay for a full set: tinyurl.com/2bt6sym Reply to this message | Report message

Fri 26 Nov 10 21:15   Amp overheating again - how much for repair? - RattleandSmoke

Just listening to Rancid Ruby Soho on the PM4000 via my Grados it sounds awful there is just no energy. As 80% of my listening is via my Grados I wonder if I am better of using this old Marantz for the speakers and buying a head phone amp? I reckon for £100 I could buy a very special headphone amplifier and then I could get any old cheap amp for my parents. The problem is a lot the music I listen to like punk is very energetic so any soft amp like the PM4000 won't work too well. Reply to this message | Report message

Sat 27 Nov 10 09:08   Amp overheating again - how much for repair? - Zero

>> The problem is a lot the music I listen to like punk is very energetic >> so any soft amp like the PM4000 won't work too well. thats the same as saying punk is noisy and tuneless isnt it? why on earth do you need to use high end kit on punk? its supposed to sound like its being played in a dustbin. Reply to this message | Report message

Sat 27 Nov 10 09:10   Amp overheating again - how much for repair? - RattleandSmoke

The Sex Pistols maybe, but a lot of punk like Joy Division and The Clash are actually very high quality recordings. I also listen to a lot of classic rock and a bit of folk rock. Reply to this message | Report message

Sun 28 Nov 10 12:55   Amp overheating again - how much for repair? - RattleandSmoke

Been speaking to some HIFI engineers about this and they reckon it is the bias which is set to high. One of them has managed to get me a circuit diagram with the settings on it for the bias adjustment. I shall attempt this in a few days when my oscilloscope arrives. I used to do a lot of electronics so something like this I should able to do sort. I am also planning of relearning the art of soldering. I suspect I might have to move my business more into the direct of electronics. Reply to this message | Report message

Sun 28 Nov 10 12:59   Amp overheating again - how much for repair? - R.P.

A chap needs an oscilloscope Rats ! Last edited by: Pugugly on Sun 28 Nov 10 at 13:00 Reply to this message | Report message

Sun 28 Nov 10 13:02   Amp overheating again - how much for repair? - Zero

I kept mine, great fun to play with. Reply to this message | Report message

Sun 28 Nov 10 13:04   Amp overheating again - how much for repair? - RattleandSmoke

It is something I have been meaning to get for a while but I have been offered a second hand one at a good price, they sell new for £140. Will be quiet handy for a few things. There has been a couple of times when I wish I had one to measure the output on certain sensors in cars too. Reply to this message | Report message

Mon 6 Dec 10 11:41   Amp overheating again - how much for repair? - AnotherJohnH

using the information found in april: www.scribd.com/doc/23336802/Cambridge-Azur640A-Pwr-Sm Cambridge Audio Azur 640A Amplifier Bias Setup To set the bias on the 640A Amplifier: Measure the voltage across R22 and R100 (Left channel) individually; they should be adjusted using Preset R116 so that the voltage measured on each resistor is greater than 13mV. This procedure should then be repeated for the Right channel by measuring the voltage across R52 and R69 whilst adjusting Preset R68 so that the voltage measured on each resistor is greater than 13mV. That's a vanishingly small voltage to measure accurately. Perhaps the question is - if it's significantly wrong, why has it changed? Also the offer of the free pot driver still stands, subject to somebody letting me know where to post it. And finally, as it's a class B amp, isn't the bias adjustment increased just to stop cross-over distortion? The setting is "greater than.." not "tune for minimum smoke". Reply to this message | Report message

Mon 6 Dec 10 12:32   Amp overheating again - how much for repair? - spamcan61

Yes, 13mV minimum sounds like a somewhat barn door target doesn't it? Anything between 13mV and supply rail is presumably OK then. I'm wondering if the hfe of the transistors is changing with age and the bias circuit can't cope or doesn't have some degree of feedback. Mind you I'm an RF guy so audio is hardly my specialist subject. Reply to this message | Report message

Mon 6 Dec 10 13:59   Amp overheating again - how much for repair? - AnotherJohnH

>> Yes, 13mV minimum sounds like a somewhat barn door target doesn't it? >> Anything between 13mV and supply rail is presumably OK then. No! Look at the diagram. That 13mV is across the 0.22 ohm (3 Watt) resistors in the emitter of the output transistor(s). Around 80 mA. If you have the a volt or two across those you'll have the fire predicted earlier. (W=Vsquared / r) Reply to this message | Report message

Mon 28 Mar 11 23:51   Amp overheating again - how much for repair? - RattleandSmoke

Just an update on this, had been using my parents (my old amp) Marantz PM4000 but now given it them back. I have been looking on ebay and put in a couple of mids for second hand amps to keep me going but I pulled out when the bids were reaching over £60. There is a basic mid 00's Sony amp for sale locally for £50 which would have cost around £150 in 2005 but my amp cost £330 in 2005. I have decided I have no choice but to take it to the local TV shop and get it repaired. I have decided against trying to fix it myself as I am not confident in working live. I know the amp is overheating not only because of the heat put the cut out indicator LED is flashing twice which means temperature overheating, e.g the thermistor has detected the amp is getting too hot so cuts out before a fire. It does this even on standby sometimes. Reply to this message | Report message

Tue 29 Mar 11 11:41   Amp overheating again - how much for repair? - Fursty Ferret

>> It does this even on standby sometimes. >> Faulty thermistor in that case! (Unless it's drawing a couple of hundred watts on standby, in which case it's quite badly knackered.) Reply to this message | Report message

Tue 29 Mar 11 12:05   Amp overheating again - how much for repair? - Hard Cheese

The CA 640A is a good amp, worth repairing. Reply to this message | Report message

Tue 29 Mar 11 12:25   Amp overheating again - how much for repair? - RattleandSmoke

By standby I meant no music going through it but the input selected and after I have played music. However even if I am just watching TV via my headphones it still cuts out after an hour and gets hot. It is a powerful amp and the maximum current draw is 640w from the mains so I would expect some heat. The fact the amp gets so hot suggests to be that the heatsinks are working fine, if the transistors were just getting hot I doubt I would feel such heat on the lid. The odd thing is when it was down stairs for a few months lately it didn't seem to cut out as much but it was being used as a TV amp and not really on very loud, it is also a much bigger room so the heat may have been able to better escape. Reply to this message | Report message

Tue 29 Mar 11 14:24   Amp overheating again - how much for repair? - Armel Coussine

Don't they have fans inside them like desktop computers? If not it would be a doddle for a techie like you to fit one, Sheikha. My desktop some years ago started overheating and crashing. It was discovered that the fan had got clogged up with dust and (AHEM! Cough cough...) tobacco tars. When a new one was fitted it worked well again. It occurs to me that the noise of a fan might be unwelcome in the same room as Lady Gaga in superb hi-fi, especially if the commutator was sparking and creating interference. But if that didn't happen you could always have the amp out in the shed and long wires to and from it. Last edited by: Armel Coussine on Tue 29 Mar 11 at 14:27 Reply to this message | Report message

Tue 29 Mar 11 15:44   Amp overheating again - how much for repair? - RattleandSmoke

It is different, the heat sinks get very hot so the cooling is doing its job, the problem is the transistors are just getting too hot. I think this is one just left the professionals, I would not expect a TV repair man to be able to remove root kits from TV repair skills nor is PC repair the same skill as working on live 240v equipment. Reply to this message | Report message

Tue 29 Mar 11 14:37   Amp overheating again - how much for repair? - NortonES2

Left-field, but have you checked your mains voltage? Ours was well over normal limits, frequent light bulb failure. I asked electrician to check. When I complained to supplier, they monitored it over a period of weeks - agreed it was well over. 257 I think. They rebalanced the phases taken off the 3-phase mains I think. Anyway, this article might be of interest:www.soundonsound.com/sos/jul03/articles/mainsproblems.asp I know nothing of the subject BTW. Just curious. Reply to this message | Report message

Tue 29 Mar 11 15:42   Amp overheating again - how much for repair? - RattleandSmoke

HIFI amps never have fans as they have to operate in complete silent :). Erm I never thought of checking the mains voltage. I have no other reason to suspect a mains problem though. We have no problems with bulbs blowing, all my PSUs are very old and have lasted (mine is 5 years old, my parents is 4 years old) all the other amps are fine etc. It is the actual output stage which is overheating too rather than the power supply unit itself. I will find out on Friday what it will cost to repair and I will decide from there if it is worth bothering. I can't really afford this HIFI hobby any more because stuff costs too much to replace/repair. Reply to this message | Report message

Tue 29 Mar 11 15:57   Amp overheating again - how much for repair? - R.P.

Rats, Check whether the voltage on the amp is 240 and not a lower one for some foreign market. Reply to this message | Report message

Sun 3 Apr 11 18:34   Amp overheating again - how much for repair? - RattleandSmoke

The amp is set at the correct voltage. I also measured our voltage at the mains yesterday and it was around 243v so perfectly fine. It tends to be when it gets above 250v it causes problems. The TV shop yesterday said they were testing the amps power supply and they suspect this where the fault is, e.g providing too much power to the output stage but they said it is probably beyond repair. I will find out tomorrow. Meanwhile I am hoping a £25 Sony amp (a basic one) is still for sale on ebay and I will buy that to keep me going and then save up to buy a decent £300 amp to last me hopefully at least until I am middle aged!. Reply to this message | Report message

Sun 3 Apr 11 18:57   Amp overheating again - how much for repair? - Zero

Rats, it never gets to 250 volts. Reply to this message | Report message

Sun 3 Apr 11 19:02   Amp overheating again - how much for repair? - RattleandSmoke

Not at the mains but if the transformer just before the consumer unit became faulty then I imagine it could be possible? A member on here said he was getting above 250v because of that very fault. A friend of mine also had the same problem although his transformer also started melting at that point. Just on a the subject the voltage range jumped around 0.6v in the few minutes I was watching it, every second or so it would drop say by 0.05v but I guess that sort of fluctuation is perfectly normal. Last edited by: RattleandSmoke on Sun 3 Apr 11 at 19:04 Reply to this message | Report message

Sun 3 Apr 11 19:06   Amp overheating again - how much for repair? - Zero

What transformer just before the consumer unit? There is only one, its at the sub station somewhere in your area. Reply to this message | Report message

Sun 3 Apr 11 19:14   Amp overheating again - how much for repair? - RattleandSmoke

We have one, I will take a picture of it in a bit but then our house has had electricity since 1906 so it might be a legacy of such an old system. There is lead cunduit which comes the house, then it goes to a transformer which says on it "Danger 420V" which also has a large sealed fuse. Then from there it goes straight into meter before going to the consumer unit. The local substation drops the 10,000v to 420v. It will probably this evening before I can take a picture, I don't think my parents will take too kindly of me posting pictures of it! Last edited by: RattleandSmoke on Sun 3 Apr 11 at 19:14 Reply to this message | Report message

Sun 3 Apr 11 19:44   Amp overheating again - how much for repair? - Zero

>> We have one, I will take a picture of it in a bit but then >> our house has had electricity since 1906 so it might be a legacy of such >> an old system. There is lead cunduit which comes the house, then it goes to >> a transformer which says on it "Danger 420V" which also has a large sealed fuse. >> Then from there it goes straight into meter before going to the consumer unit. Good lord! you sure its a transformer? Anyone else got one of those? Last edited by: Zero on Sun 3 Apr 11 at 19:44 Reply to this message | Report message

Sun 3 Apr 11 19:46   Amp overheating again - how much for repair? - rtj70

No wonder his amp is overheating. 420v mains ;-) Never heard of this before. Wiring in our old house was old when it came to the fuses.... but it was a normal supply. Only extra bit was the circuit that stepped down the power for a feed to the garage (stepped back up at the other end). Reply to this message | Report message

Sun 3 Apr 11 20:30   Amp overheating again - how much for repair? - PeterS

415V is 3 Phase isn't? Used in industrial applications I thought - not sure what is doing in a domestic environment??? Reply to this message | Report message

Sun 3 Apr 11 20:04   Amp overheating again - how much for repair? - spamcan61

Given that a normal 3 phase supply is 415V I'm wondering if this is actually a 3 phase transformer lurking in a domestic residence for some reason. Reply to this message | Report message

Sun 3 Apr 11 20:26   Amp overheating again - how much for repair? - Zero

Yeah, I figure he has three phases coming up the lead sheathed cable, and should have one phase tapped for the house. Reply to this message | Report message

Sun 3 Apr 11 20:30   Amp overheating again - how much for repair? - RattleandSmoke

It is indeed 415v my memory failed me. The house was rewired in 1980 and a new meter was installed in 2007 but these houses were unusual in the fact they had electric lighting from day one so I don't know if that is some sort of legacy. The cover which contains the master fuse appears to be made out of some sort of ABS plastic. I don't know if this was installed in 1980 or earlier. I am guessing it was just the way the electricity board supplied the electricity in this area. I wonder if Ted could confirm his setup? His house is 15 years newer and will have a different substation but will be the same supply. i167.photobucket.com/albums/u141/amazingtrade/P1050816.jpg i167.photobucket.com/albums/u141/amazingtrade/P1050815.jpg i167.photobucket.com/albums/u141/amazingtrade/P1050818.jpg All this is just before the Wylex standard 60amp 8 way consumer unit. Reply to this message | Report message

Sun 3 Apr 11 20:39   Amp overheating again - how much for repair? - Zero

there is no 60 amp transformer there. The 415 volts label is what the block is rated for. you have 240 volts just like the rest of us. Reply to this message | Report message

Sun 3 Apr 11 20:41   Amp overheating again - how much for repair? - RattleandSmoke

Even though the sticker is on the fuse itself? Also what is that fluvent box just before the metre? Reply to this message | Report message

Sun 3 Apr 11 20:47   Amp overheating again - how much for repair? - Zero

Fluvent is the name of a electrical manufacturer from Manchester that folded in the 1970s. The box is a distribution box. A 60 amp transformer would need to be quite big. There is nothing there large enough to be one. Reply to this message | Report message

Sun 3 Apr 11 20:54   Amp overheating again - how much for repair? - RattleandSmoke

I would imagine it would buzz a bit too and it is completely silent :). Thanks for clearing that mystery up. So when my mates melted it must have just been the fuse. I wonder how old that mains fuse actually is? I know the house was re-wired from paper/cotton to rubber in the 1950's but those boxes look a lot newer than that. It was then rewired from rubber to PVC in 1980 and that installation is what we still have. Reply to this message | Report message

Sun 3 Apr 11 20:57   Amp overheating again - how much for repair? - Zero

>> I would imagine it would buzz a bit too and it is completely silent :). And it would be just a touch warm! They have to cool large transformers in oil! Last edited by: Zero on Sun 3 Apr 11 at 20:57 Reply to this message | Report message

Mon 4 Apr 11 02:02   Amp overheating again - how much for repair? - devonite

yep! - `fraid we have, tis on the wall in the lobby wired up just as the man says! fastened to a bit of board off the Ark and screwed to the wall through ceramic insulators. Reply to this message | Report message

Mon 4 Apr 11 15:38   Amp overheating again - how much for repair? - RattleandSmoke

Got it back, they can't fix it because they can't get the diagrams from Cambridge Audio. They have said only Richersounds can fix it, they want £40 just to even look at it. They go for around £130-£150 second hand on ebay but most go for £30-£40 because they are faulty. I think I am best getting shut of it, it is a good amp when it works but I won't be happy paying £100 for something else just to go wrong with it. Trying to source a temporary amp until I either get it repaired or save enough pennies for a new one. Reply to this message | Report message

Mon 4 Apr 11 15:53   Amp overheating again - how much for repair? - spamcan61

Tell them about the 'Google' interweb thing! www.schematicsunlimited.com/download.php?manu=cambridge-audio&file=cambridge-audio-azur-640a-power-amplifier-service-manual.pdf Reply to this message | Report message

Mon 4 Apr 11 16:07   Amp overheating again - how much for repair? - RattleandSmoke

I think they just didn't want the job. It is really a TV repair place. There is a HIFI repair shop opposite but they wired up a pair of headphones I ask them to repair back to front once so never again. Just need to find a dedicated HIFI engineer I guess. Thanks for the link, at least I it might be useful. What they were saying even if they had the diagrams they wouldn't be able to get the parts. At least if I stick it on ebay I can sell it with the schematics. Last edited by: RattleandSmoke on Mon 4 Apr 11 at 16:08 Reply to this message | Report message

Mon 4 Apr 11 16:14   Amp overheating again - how much for repair? - spamcan61

As you say it sounds like they just didn't want the job; I'm not an audio electronics boffin but a quick look through the circuit diagram didn't show anything particularly exotic. I suppose there is so little market now for domestic electronics repairs that it will be tricky finding anyone to take it on at a sensible price. Reply to this message | Report message

Mon 4 Apr 11 16:33   Amp overheating again - how much for repair? - RattleandSmoke

I might ask my uncle, he knows a lot more about me about electronics, he used to fix our TVs etc so might be able to look at this now I have the diagrams. In the meantime I have seen a mid spec Sony amp for £50 on gumtree it will keep me going till I either find £400 for a new amp or get this repaired. It is just a shame these old amps are getting hard to find. Just need anything which can deliver 50w RMS into an 8 ohm load. A HIFI forum reckoned it could the bias set wrong on my amp but I just question if that needs adjusting something must still be faulty to cause that. Reply to this message | Report message

Mon 4 Apr 11 17:01   Amp overheating again - how much for repair? - spamcan61

>> >> A HIFI forum reckoned it could the bias set wrong on my amp but I >> just question if that needs adjusting something must still be faulty to cause that. >> Yes, my first guess would be either an output device or one of its bias components has drifted out of spec. Reply to this message | Report message

Mon 4 Apr 11 17:22   Amp overheating again - how much for repair? - Zero

My first guess would be its crap design, Bin it. Reply to this message | Report message

Mon 4 Apr 11 19:49   Amp overheating again - how much for repair? - Bellboy

>> My first guess would be its crap design, >> >> Bin it. >> >>>>>>>>. agreed its probably like an old amstrad 3000 once the covers off transformers made of cheese Reply to this message | Report message

Mon 4 Apr 11 20:25   Amp overheating again - how much for repair? - RattleandSmoke

Just trying to win an amp now :). If I get it it will be an ideal amp to keep me going until I get something better sorted. I am not going to pay silly money for it though. I really regret getting rid of my old Marantz now, it only needed a new balance pot and sold it cheap at the time they were not worth much but they have increased in value. Reply to this message | Report message

Mon 4 Apr 11 20:27   Amp overheating again - how much for repair? - Hard Cheese

>> >> My first guess would be its crap design, >> >> >> >> Bin it. >> >> >> >>>>>>>>. agreed its probably like an old amstrad 3000 once the covers off >> transformers made of cheese >> No, it is a good amp. Reply to this message | Report message

Mon 4 Apr 11 20:56   Amp overheating again - how much for repair? - RattleandSmoke

I won an auction for a Yamaha AX392 for £40 and pickup, it will keep me going for a bit and I can easily sell it so it won't cost anything. I will ask my uncle to have a look my existing amp which will take a while but at least I will have a backup :) Reply to this message | Report message

Mon 4 Apr 11 22:05   Amp overheating again - how much for repair? - Hard Cheese

>> I won an auction for a Yamaha AX392 for £40 and pickup>> Good amp, I have a classic AX300 and an AX390 somewhere, both actually look very contemporary today and the more simple 300 in particular is excellent. Reply to this message | Report message

Mon 4 Apr 11 22:32   Amp overheating again - how much for repair? - RattleandSmoke

Not actually listened to one, I am a bit worried the sound might be a bit soft with my already soft Whafedale Diamond 9.1s but I use my HIFI mostly with my Grados and mid end Rotel pre amp anyway so this amp is simply going to be used to play music before I go out so as long as it sounds better than the Marantz PM4000 I was using I will be happy. I think these were only around £200 new though weren't they? I can find very little information but the 60w RMS into an 8 ohm load will be more than fine, the Marantz was only 35w and that did struggle. Reply to this message | Report message

Tue 5 Apr 11 21:40   Amp overheating again - how much for repair? - RattleandSmoke

Been listening to the Yamaha for a couple of hours now and its just running luke warm. It can't quite handle some of the dynamics as well as the Cambridge and it sounds a little bright with my Grados but I have the Rotel pre amp for that. Either way I am dancing as I listen to it, which I couldn't do with the Marantz PM4000 I was using (my parents). The sound is very punchy. With my speakers it is fine, I would have liked a little bit better timing in the bass but it has very good soundstage with my Diamond 9.1 speakers. For £40 I really cannot complain, I use my headphones most the time anyway I only really use the speakers before going out on a Saturday night. I reckon it would have sold for around £220 back in 1996 but I can't find any exact prices to buy something as good on the new market I think I would have to spend around £250 so it is a bit of a bargain in that sense. It is a lot better than my parents Marantz PM4000 which I had been using. The only thing I don't like is only the CD input has a direct input switch but I think this was common in the late 80's to late 90's, modern amps either do without tone controls or have a switch to bypass the lot. It has a remote control too which surprised me. i167.photobucket.com/albums/u141/amazingtrade/yamahaamp.jpg Last edited by: RattleandSmoke on Tue 5 Apr 11 at 21:41 Reply to this message | Report message

Tue 5 Apr 11 22:18   Amp overheating again - how much for repair? - Hard Cheese

>> The only thing I don't like is only the CD input has a direct input >> switch but I think this was common in the late 80's to late 90's, modern >> amps either do without tone controls or have a switch to bypass the lot. >> CD direct is a switch to bypass the lot though works on the CD input channel only. Reckon the 392 is approx '98 - '99. My 390 is circa '96 - '97 and basically the same though without the controls hidden behind a hatch as on your 392 (and the 397) and hence looks even more contemporary today. Reply to this message | Report message

Tue 5 Apr 11 22:26   Amp overheating again - how much for repair? - RattleandSmoke

The seller said it was 1996, but I think it would be newer that as it is remote driven. Do you know where these amps fitted in terms of range? Where they bottom end budget amps or more lower end mid range? The 60w per channel suggests its lower mid range. Looking inside I can see quite a few components are cheaper than my Cambridge but then that lasted three years and this amp is a lot older than that. Still for £40 I get my music back. I would say compared to my Cambridge the bass is not quite as deep or fast and some of the subtleties are amplified a bit too much but the treble is a lot sweeter on this. It sounds better now is warmed up. I don't think I could have bought anything better for £40 Last edited by: RattleandSmoke on Tue 5 Apr 11 at 22:29 Reply to this message | Report message

Tue 5 Apr 11 22:32   Amp overheating again - how much for repair? - Hard Cheese

At the time it was perhaps the cheapest Yamaha amp though probably classed as mid range. Reply to this message | Report message

Tue 5 Apr 11 22:41   Amp overheating again - how much for repair? - RattleandSmoke

I am surprised that it dosn't really seem that highly regarded. The 492's are going for silly money (£100+) but for the under £50 they could make a very good basis of a budget audiophile system. Reply to this message | Report message