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Started by bubbastain, August 11, 2012, 05:54:09 PM

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bubbastain

N
 :o

J M Fahey

Beyond cool.
Forget brand, replace any electrolytic capacitor with a new one, same specs of better , as in it may be easier to get a 25V cap (the next higher value) instead of a 16V one amd maybe you don't find, say, a 1200uF one, thenmuse 1500uF or in a nutshell the next higher value.
Are you sure it's "oily"
Because electrolytic caps leak a,heavy salt and salt solution, which is not oily but water soluble.
If really oily, clean with arag with a few drops kereosene, turpentine or alcohol; if it's some kind of thick brine with a cloth wet in warm water .
Clean, rinse the cloth under tap water, repeat 3/4 times, finally dry with clean paper towels.
That fluid is corrosive and will eat the metals.
If in doubt clean the whole insides with pure medicinal ethylic alcohol (not *rubbing* alcohol) and a brush, try to wipe the grime towards one side and absorb it with paper towels.
Repeat 3/4 times.
WARNING: alcohol is flammable.
Do not smoke and do it in a ventilated room, or in the garage with all doors open.

Roly

Cute little amp.   :tu:

I agree with JM, this doesn't look like cap gunk but something else that has found its way inside (misconceived attempt at cleaning with some chemical/lubricant spray, over the top pot cleaning?).

You would be amazed at the sundry residues techs find inside gear.  I'd follow JM's cleaning advice rather than trying any sort of "mystery spray".  I've been known to give amp innards a brush down with dishwashing liquid in warm water which is okay provided you avoid transformers and pots, rinse it all off, then (carefully/gently) dry well with blow heater, hair dryer, or just leave in a warm sunny spot.

The cap looks, from it's position, like it might be the output coupling cap, so going up in value is normally not only harmless but can make a small improvement to reliability.  But if it's not actually leaking I wouldn't bother replacing it, just give everything a good clean.

Remove and renew the reverb line mounting foam.

Circuits for this general style of amp are almost unknown unless you are lucky enough to find a user trace; manufacturers simply didn't publish them, but the circuits tend to be quite generic.  Output transistor type numbers?
If you say theory and practice don't agree you haven't applied enough theory.

teemuk

A lot of dirt I see there looks like generic lacquer, flux and glue. Those may react strangely when aging; e.g. changing colour, turning "powdery" etc. You'd also be surprised how much that flux stuff also spatters around when soldering.

And the photos have a habit of usually making everything look way worse.

Leaking caps excluded, if it's a small effort I'd clean the dirt off as much as I could but otherwise I don't know how much I'd worry about it. It's probably been there ages already. I once fixed a Japanese amp from the same period of time and it was pretty much in similar condition internally: Plenty of flux residue everywhere, and both component glue and protective lacquer sprayed on the component side of the board had turned brownish and dirty looking. Perhaps there was a bit less mess. The cushions of the reverb tank at least weren't soaked.

Roly

Yeah, but teemuk, he says it's oily; that doesn't sound like flux residue to me which, as you say, goes brittle and powdery.

It reminds me very much of a radio station mixer that had been given so many sprays with some mystery cans of "instant technician" that there was oil actually running about in the bottom of the chassis (and something in the stuff had made all the cap seal bungs swell up and pop out - 'orrible), 'tho in this case it doesn't seem to have actually damaged anything except the reverb tank foam supports.
If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

Maybe somebody did what you .... er .... wanted to  ;) and sprayed it not with cleaner but with WD40 type oil.
A LOT of it, maybe along many months.
Sprayable oils are usually made of a not so light oil, mixed with a solvent to make it thinner (similar to white kerosene) and a propellant, either Freon in the old days and today propane or similar.
A few days after you spray them, all volatile solvents evaporate and the relatively thicker oil stays behind.
And any petroleum based product *eats* foam , so the thick gunk you see may be a mix of both.
I'd scrape old foam, clean whatever's needed and apply new one.
It must be rotting anyway because of age.

Roly

@JM "WD40" - quite so.  I don't trust cans of "instant technician" (e.g. CRC) because they are very coy about what they put in them, and there are a range of different formulations for different uses which look similar, and non-technical types (and sale people) tend to think that "CRC", whatever it actually says on the can, is "contact cleaner".  The particular one I encountered in the mixer was actually for moisture proofing motors!  In that case its regular application had, I surmise, caused the light fractions to attack the electro cap seals. {and all that spraying was instead of actually replacing some scratchy pots of a common type - go figure}.

@bubbastain - I only advise replacing the foam 'coz it's generally a lot easier than cleaning it, and most of these foams seem to have a fairly limited life anyway before they start to break down and either go powdery, or even liquify.  But by all means try washing them out if you can be bothered.

If it had been sprayed with oil in the factory it would be the first one I've ever seen, and I can't think of any good reason for it.  I'd be more inclined to think it was a prior owner who perhaps lived near the seaside and was trying to protect it.

Nice walk-through vid.  :dbtu:
If you say theory and practice don't agree you haven't applied enough theory.