Kustom "Frankenstein"

[JHow]

I have a Kustom "Frankenstein" style head whic I can't ID.  It does not appear to have any numbers on the PCBs.  It is very bare bones, two channels, Treb, Bass, Volume each channel, six TO-3 RCA transistors on the back labelled 36892. No "200" on the front plate, just "Kustom", but I am assuming that's what it is.  It looks all original, everything coated in a fine layer of grease, it works but has odd intermittent bursts of noise, kind of like an AM radio during a lightning strike, almost like dirty pots but it happens on both channels and is independent if turning any of the controls.  The controls do what they are supposed, volume makes it louder, bass makes it brassier, treble makes it trebly.  I haven't made any measurements yet, because I am hoping you guys might steer me to the closest PCB schematic. I assume there is a lot of similarity in the boards?

[tubeAMP]

grease ?  was it in a restaurant kitchen ?  that would make it greasy
have yo checked the speaker connections ?  normally closed contacts ?

[DrGonz78]

Yeah Grease what a great musical...   Oh no this kinda grease not so wonderful at all. Lubricated cleaning solutions might have been sprayed into the pots from the front side of the amp. Or worse and more probable those same solutions were sprayed right into the input jacks to clean them out. Now years of this cleaning procedure can leave an amp completely greasy for the rest of it's life! Either that or it was a practice amp used by a Colonel Sanders employee while he was cooking. Yeah playing gigs at restaurants could be the culprit to some degree too.

Anyhow 100% alcohol will help clean off the grease. I was told by greater minds that kerosene works great at removing the oils from the boards. No not burning it! Personally don't power up that amp or do any trouble shooting till you fully clean the heck out of it and try to get the oils out. It will be a chore, depending on how bad it is, good luck. 

[DrGonz78]

Oh yeah BTW... Here is a good site to reference the pcb board number and try to find your exact schematic. It is under the technical link on their pages.

http://www.vintagekustom.com/

[JHow]

Okay.  I'm breaking out the alcohol.  Here is a picture...

[g1]

  What a coincidence, I was just breaking out the alcohol too!   
Looks like restaurant/bar grease/nicotine type residue, probably was in the same place for a long time.
  Dr.Gonz:  as far as the kerosene goes, I don't think it evaporates so I wouldn't recommend it.  I filled a pail with some and forgot a motorcycle chain in there about 5 years ago, no lid and the pail is still full.

[JHow]

Dr Gonz:  Thanks for the link.  It looks like the first link under "200" is the right one, ignoring the reverb and vibrato boards, which i don't have.

I was halfway through the alcohol when I realized you meant for me to clean with it. 

I just finished wiping it out.  It looked like this amp was last serviced at jiffy lube.

[Roly]

I was halfway through the alcohol when I realized you meant for me to clean with it.

:lmao:

Oh boy, that's real fish & chip shop territory!  You don't normally see this outside radios that have been in a commercial kitchen for a few years.

If it were me I'd be using warm water with a good shot of dishwashing liquid applied with toothbrush and similar, carefully avoiding the pots and trannies, followed by clean warm water rinse (applied ditto to remove the soap+grease), followed by a liberal metho rinse (to carry off the rinse water), followed by a good shake and a dry out in the sun (or just somewhere nice and warm if it's snowing outside).

Normally the problem here isn't the actual grease, which should be non-conductive, but the dirt that has accumulated in it plus a bit of humidity.  Pure water is actually a pretty good insulator, but add some contaminants, seaside salt in particular, and you end up with a resistive film that randomly changes value.  In fact one way to create a slow noise generator is a couple of electrodes stuck in some cotton wool damp with salt solution.  The pots will also need a clean with some contact cleaner.

The underside of the transistors where the leads come out require special cleaning attention.  Done right this should cure your noise problem.

Good luck, and let us know how you get on.

[J M Fahey]

Kerosene is fine: *great* degreaser, *kind to plastics* , absolutely non conductive , much less flammable than alcohol (just shower both with sparks from an emply lighter and check which one goes up in flames) and *does* evaporate.

Can't elaborate on the motorcycle chain/5 years  bit, but given the bike shop environment suggested, after cleaning a dozen bike chains and assorted other parts, that fluid might be 95% grease/oil by now .... and *that* certainly won't evaporate...... but I wouldn't call *that* kerosene.

In fact I use kerosene and a medical syringe, complete with needle, as a residue free pot and switch cleaner, go figure.

Was introduced to its properties by a Guitar Luthier guy who had a magical way to clean grime/nicotine/tar out of any electric guitar, just wipe it everywhere with a clean rag, with some drops of kerosene, repeat with another clean one.
Squeaky clean results , literally.

[g1]

  Thanks JM, you're right, the goop in my "parts cleaner" pail is probably mostly oils now and very little kerosene.  It may not evaporate as fast as some other fuels, but that doesn't mean it doesn't evaporate.  I guess the key is to wipe off as much as you can and the rest should evaporate.

[JHow]

Well I followed the warm soapy water on a rag, then damp tag then alcohol.  I tried to clean all the transistor connections/solder joints. I unbolted ( but not un soldered) the boards, the big filter caps, the pots, and cleaned everywhere I could reach.  I put it back together and I am happy to report it is substantially improved.  I haven't played it long enough yet to know if it has any other issues,  but the bath really has helped.

I am intrigued by the kerosene comments.  I have heard if using naphtha, like lighter fluid to clean guitars.  I guess it is similar to kerosene.

[Roly]

I am happy to report it is substantially improved.

Excellent, that's what we like to hear.   :dbtu:

With cleaning stuff you sometimes have to go around again to get the last of the gunk out.  I know I've sometimes had to revisit coffee-in-synth repairs (particularly if they like their coffee sweet     ).

[J M Fahey]

Naphta/lighter fluid is great, but is spark ignitable and puts out lots of flammable/explosive vapours, so humble kerosene is safer.

The typical naphta accident (home destruction and deaths included ) around here in Argentina is as follows: naphta is popular for dry cleaning greasy stains on clothes, specially those which can't be machine washed, such as business suits, so some guy who has to clean a carpet has the bright idea of doing the same.
Of course "he's no fool" so he works with doors and windows open.
So far so good.

Problem is that then he closes them for the night ... during which time remining fuel on carpet evaporates and makes an explosive mixture.

Next day somebody comes, turns the light switch on ....... and puts himself in orbit .... without a spaceship or spacesuit.