Tutorial: "Deep Cleaning" An Amplifier

Great thread! :thmbsp: Glad it was made a sticky.

If anyone has a large enough food dehydrator (the kind used to make dried fruits and such), it makes a great way to dry off circuit boards. A local Salvation Army had several at a cheap prices a couple of years ago. I got one for food, and one for this kind of use. The biggest PCBs don't always fit in the one I have, but when they do fit, it does a quick and effective job of getting the board really dry (and warm! :D). Sometimes I'll "assembly line" the boards, washing several in quick succession and doing a quick partial-dry with the (professional) blow drier before putting them on the trays/racks in the dehumidifier. Then turn it on when the last one goes in. In a short time. the boards are all nicely and COMPLETELY dry. If you want to try this, just make sure the trays are tall enough to handle boards with mounted components: sometimes they are too shallow.
 
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maybe you didn't say "Bitte" the first time?

I thought I did :sigh:

original thread said:
how do you clean and amp?

Bitte me,

Danke

:D Actually I've gotten almost all of the above info from various folks here several times, but I forget faster than I type, so I've asked again and again. Still, having it in one place with pictures is really good for me.

So thanks to all who have had to tell me the same thing 30 times before it actually sunk in!!
 
Great thread! :thmbsp: Glad it was made a sticky.

If anyone has a large enough food dehydrator (the kind used to make dried fruits and such), it makes a great way to dry off circuit boards. A local Salvation Army had several at a cheap prices a couple of years ago. I got one for food, and one for this kind of use. The biggest PCBs don't always fit in the one I have, but when they do fit, it does a quick and effective job of getting the board really dry (and warm! :D). Sometimes I'll "assembly line" the boards, washing several in quick succession and doing a quick partial-dry with the (professional) blow drier before putting them on the trays/racks in the dehumidifier. Then turn it on when the last one goes in. In a short time. the boards are all nicely and COMPLETELY dry. If you want to try this, just make sure the trays are tall enough to handle boards with mounted components: sometimes they are too shallow.

An old food dehydrator sounds like a good plan. I also think that one can build a simple "drying cabinet" using a PC fan and a 100 watt light bulb + thermostat.
 
Nice, now I just need to get an amp that has so few components :)

Hot soapy water does wonders.
 
Hey thanks for this great thread. Just tried this out on a very dirty Pioneer that I was planning on recapping, worked great! Better than new I would say:yes:
 
Definitely a good read! I would add a few things.

2) If you get the powdery white mess after cleaning the board, you can either clean it again, try the turpentine method, or you can use a bit of WD-40 on a cloth. The white stuff doesn't hurt anything (it's anhydrous rosin), but it's ugly for sure.

That `white powdery stuff´ condition happened to me. In the lab at work, they use acetone to remove solder flux from PCBs. I bought some and put it in a pump dispenser, then snipped off an acid brush short with scissors to form a stiffer brush. Repeat this process and use compressed air until the circuit side is sparkling clean. Note that Acetone will remove marking pen and other inks from the PCB.


-Gregory
 
My little contribution is this: be careful for grounding wires soldered to the chassis. On my Kenwood KA-8100 both the front and rear chassis plates are used as grounding points, so I had to be really careful with these wires. At first, I didn't know they were there, and I nearly damaged them. But once I figured out what was going on, I was able to either work around them, or de-solder and re-solder the wires as needed.

Great tutorial, I can't wait to try it on my next project!
 
Great stuff, but some questions.
Why shouldn't we soak a transformer or choke in liquid?
Can I use alchohol instead?
What about coils that are wrapped around a plastic core?
How about multi value caps such as the can type?

I do have a project radio that has some burn damage around the power supply, basically black soot covered.
Thanks In advance
 
Great stuff, but some questions.
Why shouldn't we soak a transformer or choke in liquid?

Well it might be OK in some cases but here's some considerations I have that keep me from doing it as a rule:
  1. Older transformers with paper wraps/interleaving and or ancient types of varnish and glue that could be dissolved or damaged with lotsa liquid. This is mainly pertinent to really old vintage gear which has stuff that was NOT designed to be soaked. I've also had carbon comp resistors in that kind of ancient gear that crack or 'splode after soaking so I've learned not to soak really old stuff.
  2. All the nooks and crannies in a txfr can trap liquids such that a glue or varnish that wouldn't dissolve from a brief washing could start to soften and be 'solved' over a longer term as it soaked and soaked inside someplace where you can't see?
  3. Likewise liquids trapped inside when you power it up could cause issues as it warms up?
  4. Transformer cores are various ferrous metals that usually rust rapidly - if there's missing or melted or dissolved varnish inside it could start rusting from the inside out from trapped water?
  5. Small sensitive tuner coils/inductors could have debris or solved adhesives or flux or other substance washed into them as well as out, potentially causing a change in value and/or seizing up slug threads?
  6. etc. that kind of thing

I WILL wash boards with coils/txfrs on them, I just get real careful around them, keep solvents away from them as much as possible, and try to ensure I don't wash anything INTO a little tuner coil. I NEVER soak a big PT or OT - there's nothing really to be gained there anyway, those are wicked easy to remove, wipe down and clean from the outside. On a SS amp in fact the PT usually comes off before I do a 'tub job'...

Can I use alchohol instead?

Lotsa posts on here already about use of alcohol... many use it, sometimes you'll get a white residue from alcohol interaction with flux residue.

What about coils that are wrapped around a plastic core?

Like your basic air-core inductor? I don't worry too much about those, again unless it's a slugged inductor with threads that can be bunged up..

How about multi value caps such as the can type?

They are usually sealed up pretty well in terms of surface washing but with an extended soak they could leak liquid inside which would likely disastrous in terms of a spectacular short on power up. I don't soak those either.
 
Excellent post and thanks for taking the time to type it up.

Question about the rewiring part: Is it overkill to replace all the wiring in an old amp or receiver? Also what wire would be good to use to replace it all. I'm looking into cleaning and recapping my Sansui 350A as well as my Yamaha CA-600 and was wondering if rewiring was something else I should look into.
 
TheDr

It is only a pleasure. My bit of giving in the scope of KARMA.

Regarding wiring: I have come to the sober conclusion that it is unnecessary to replace internal stock wire with monstrous cable as thick as my thumb. Use the same gauge wire that the manufacturer used. (I do have to add that some high current amplifiers could benefit from slightly thicker wire).

On the other hand if you want to rewire i.e. with pure silver wire it remains your choice.
 
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