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Old 1st October 2011, 05:48 AM   #1
seebert is offline seebert  United States
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Default Cleaning dust from old amp - advice please.

Hello all. I know a lot has been said about cleaning out old amps but I'd really like input from the very knowledgeable members here on DIY audio. I acquired an Adcom GFA 5800 (not mark II) some time ago in GWO but didn't get around to using it in my own system and am I glad I didn't - I have just lifted the lid and it is unbelievably filthy inside although that's the way it came and it was working just fine in the other guy's system, not even a hint of overheating. There must be 20 years of dust (and a few cobwebs too) in there but otherwise as far as I can tell it looks 'unburnt' in any way and in completely original shape. I've read a lot of posts about cleaning out amps etc. and some say use compressed air while some say don't, others say use a vacuum cleaner and natural bristle brush and some say strip the whole amp down to nuts and bolts which I'd rather not do at this stage. Nobody seems to like the 'pre-packed' computer type airspray cans that apparently leave a 'bad' residue where you don't want residue! The most accepted general concensus seems to be to use a grounded wrist strap and work the dust free with a softish brush and suck it up with a vacuum as you go. So, what's the best and safest way to get the amp back to pristine shape? Any and all advice welcomed. Thanks, Mike.
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Old 1st October 2011, 06:06 AM   #2
49 - for the 18th time - again!
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Hello seebert - I have cleaned and repaired many types of electronics equipment for longer than I care to admit. Much of that experience was at the level of complete restoration which included a through cleaning (I'll skip over the other details to save time and typing). A soft natural bristle brush and vacuum is your best way to go. Synthetic bristle brushes can build up a static charge so try and avoid them. Do wear a ESD wrist strap grounded to at least the amplifier case and preferably to earth ground. I like to have a selection of brushes but 2 inch and 1 inch are the ones I use most often. More advanced cleaning can involve the use of mild detergent and purified water combined with blow drying - but this should be approached with a little caution for the beginner.

Hope this helps - and if you have questions just post 'em.
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Old 1st October 2011, 06:23 AM   #3
seebert is offline seebert  United States
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Many thanks c2cthomas. I'll use your experience gladly !! While I'd really like to do it properly and get 100% of the 'murk' out of it I don't have the steady hands, decent eyesight or the confidence these days. I don't know why they call this time of life 'the golden years' ... it's more like the body is willing but all the rest is weak - if present at all. I'm uploading a pic of the amp as it is now ... hope it shows the debris in there. I'll post a pic of the finished job when I've given her a much needed (and deserved) facelift.
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Old 1st October 2011, 09:52 AM   #4
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Put amp in car, drive to garage, use the high pressure air hose you use to pump your tires and blow it all clean....
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Old 1st October 2011, 10:36 AM   #5
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I do this several times a month. Compressed air and natural fibre brush does it for me, but make sure your compressor has a oil/water filter inline. Oh, and you might want to work outside.
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Old 1st October 2011, 11:58 AM   #6
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Back in the days when I was servicing computers I used a standard air compressor outside with a few layers of rag over the nozzle to reduce the pressure and catch any water coming through, another useful combo was a vacuum cleaner on a low setting and an anti static brush.

You can always buy the cans with a compressed inert gas but they are expensive and unlike the vacuum cleaner will shoot the dust in all directions.

When I was servicing embedded computers from the mining industry we used Freon (poured in a container and brushed on), although I know better now!!
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Old 1st October 2011, 12:43 PM   #7
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Quote:
Originally Posted by digits View Post
Put amp in car, drive to garage, use the high pressure air hose you use to pump your tires and blow it all clean....
I don't know if that was an attempt at humor or simply idiotic advice. I do hope no one would take a good amp and do something that dumb.

I think the other advice given is spot on. I would aslo suggest that before any speakers are hooked up you 1) look carefully at the boards to see if any electrolytic caps have leaked, 2) use a voltmeter and check for any DC voltage coming from the outputs. I don't know the spec on that particular model, but it should be less than about 30-50 mV.

Good luck
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Old 1st October 2011, 02:18 PM   #8
seebert is offline seebert  United States
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Thanks to all for the great advice. I think I'll steer clear of the garage air hose however. So far so good: used Q-Tips (carefully) and a natural bristle brush as advised, sucking up most of the dust and 'webs' with a small vacuum. Pic uploaded.

I measured the outputs from switch-on and the levels wandered a bit but stayed below 10-12 mV settling down to 3.2mV (R) and 2.8mV (L) ... I didn't leave it on any longer until I'd checked in with you guys to see if that's okay and if there are any other measurements I should take whilst the lid is off. I know what bias is but don't know how to measure it - would doing that be of any value or not? The fans come on but at very low speed and barely audible if that's anything to go by. Even when it was dirty and I heard it before I got it they ran faster but were still quiet even when the amp was pretty well warmed up.

The meter I used is supposed to be a good one - made in the UK it's called a Metrotest MIC 3900 true RMS multimeter.

Thanks again for all the advice: if there's anything else to do (preventive maintenance or otherwise) now would be the time to do it so please advise away - I'm all ears and want to learn all I can. Best to all, Mike.
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Old 1st October 2011, 02:49 PM   #9
49 - for the 18th time - again!
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Hi Mike - as we like to say in the South - Good on ya boy - ya done fine.

Orrrrrrrr - from my USN days - OUTSTANDING!!!!! Now drop and give me 20!!

A service manual is available over at h-fi engine - you will need to join (free) in order to have access to the files. You haven't mentioned if you have any electronics experience or training so I'm unsure of you skill set with the electron thingies - but you have mad skills with the cleaning brush!!!
Adcom GFA-5800 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
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Old 1st October 2011, 02:51 PM   #10
seebert is offline seebert  United States
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WithTarragon: yes I visually checked all elecrolytics and they appear fine to my eye - no leakage, bulging or cracking. Thanks again, Mike.
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