How to deep clean a tube amp

Chassis cleaning 1:

I've heard tell of people putting chassis in the dishwasher for a through cleaning treatment but I've never done that. Additionally, with an integrated amp or receiver there are parts and pots that may not tolerate that too well, where with a standalone amplifier, those sensitive parts are not there or there aren't many of them and they can be more easily removed or masked off.

A word of caution: Many chassis are cadmium plated. If you see white powdery oxidation on the chassis, use a mask when performing these procedures and thoroughly clean everything afterward.

Step 1: The first step of chassis cleaning is to remove any rodent detritus, dust, birdseed, and anything else by taking the amp outside and vacuuming or blowing air on it.
I used canned air, like you'd use to clean a keyboard and a brush from a dustpan and brush set.

The cleaning chemicals you use to clean the chassis are your choice. I'm only describing what I do and what I use. I've heard that some get fine results using Simple Green, 409, and a variety of other cleaners. The choice is yours but the amount of elbow grease you must apply, and the state of the silk screen on the chassis may depend on your choice.

I suggest that you wear protective rubber or latex gloves for this part of the cleanup.

Step 2: I make a mixture of one part ammonia and four parts warm water in a slop sink in the basement. Make the water hot and the fumes are too much, at least for me.
Then, using a sponge paintbrush or an old rag, brush some of the liquid mixture onto the chassis and let it sit a few minutes. You don't want to use so much liquid that it drips through the chassis vent holes . Then wipe with a dry cotton rag. The purpose of this first application is to soften the oxidation, dirt and any rust that is on there for removal with a second application.

Step 3: Fill a small plastic container like you get take-out food in with an inch or so of the solution from the sink and drop the knobs in to let them soak.

Step 4: Perform a second application and then begin wiping the solution off firmly. I like to use an old facecloth and a couple fingers. Dip a corner of the facecloth in the water/ammonia solution for use where extra rubbing is required. Pick one corner of the chassis and start firmly wiping and drying the solution while changing the rag's wiping surface regularly. You can watch the black accumulate on the rag as you go. Do this until the chassis is thoroughly dry. For an especially grimy chassis, those white very low abrasive scotch-brite pads can be used instead of a rag. Don't bear down too hard where there is silk screening or where there are stampings on the chassis.

Step 5: When finished, drain the slop sink, thoroughly rinse the rag or scrubbie n water and then wipe the chassis down with a damp clean rag to remove any ammonia that may remain.

Step 6: To clean the knobs, use a toothbrush and, frequently dipping the toothbrush in the ammonia/water solution in the knob container, brush in the direction of the lines. I go from back to front in the direction of the lines on the knobs, but some knob types are smooth and that advice doesn't apply. Be careful around any gold leaf or silver position indication markers if there are any. Rotate the knob until the whole thing has been brushed. Do this for each knob. Rinse the knobs with clean water and dry them, shaking the water out of the inner and outer folds of the knob that can retain water.

I think it is wonderful what you are doing here (taking the time), but I would respectfully submit that one NEVER use ammonia or ammonia based products (Windex) to clean plastics.
Most especially on well aged, well out gassed plastics.
A one time event as you describe will in all likelihood cause no problems, and I'm not picking at your technique.
Ammonia can have a "drying" effect on plastics; suffice it to say, without going all in to it.
That is why it is NOT recommended for cleaning plastic eye glass lenses.
I have had ammonia solutions cause white spots on dark plastics.
To be safe (and it does an excellent job) use "Dawn", (obviously my favorite and I think the best) or similar, liquid dish washing soap.
I also use "Dawn" on face plates and dial rulers.

Thomas
 
Fair enough. Thanks for the feedback.
I've made the changes.

Leave the tooth brush part, absolutely! Indispensable. I used to soak knobs, but be prepared with your glue; soaking (causes no harm) but often leads to helping the old glue let go on your "brights".

I just stand at the sink with warm water running slowly, lather them with "Dawn" and brush the Hell out of 'em.

The first run the lather will often come up with a hint of the color of the plastic. It really did on my 500-C project.

It's not damaging; the mild soap is removing the "dead" plastic molecules on top. You will be left with a knob that has a nice healthy luster, as new. It really is an amazing transformation. Soap 'n' Water are my best friends.

I thought my Fisher knobs were going to just be dull, dried out shit brown, not the case.

I did use YOUR ammonia/water ratio to clean my chassis; SUPERB outcome. Couldn't stick that chassis under the faucet and the ammonia leaves no residue. I used to use alcohols (OK results), your solution works better, cheaper and will remove organic dirt that alcohol will not.
 
Hey Don,
Great thread and timely too.
I recently acquired a pair of Eico HF-22 mono blocks that are totally disassembled. Everything is getting new paint.
Your info on painting the xfmrs spurred me to paint the bells on the power xfmr black and the fins the same as the chassis' hammmered metal finish...ought to be a great look.:thmbsp:
Thanks, as usual.

Martin

P.s. My 800c is playing flawlessly! :thmbsp:
 
Martin,
I've been following that thread. You have courage. I haven't attempted a gut and rehab yet, but I have plans to.
 
I think this is close to being done.
I plan to put the thumbnail pictures in the front and complete reassembly.
Can anybody think of anything I've missed . . . other than reassembly, which I plan to complete? Is there something you'd like to see added or things to do differently?
 
Don, this is just an outstanding thread! Thanks for the time and commitment that was obviously necessary.

It's interesting how many of your suggestions are ones that I've settled on as well! I love those little dental brushes for cleaning tube sockets. Pipe cleaners work very well for larger sockets, and I used to be able to find some that had stiff little scrubby bristles among the softer fuzz. I usually use newspaper tucked around and under transformers, but paper towels are perfect, too!

Great job!

Stickied!
 
Last edited:
WOW. "Thorough" doesn't even begin to describe it! If/when I am able to get at the guts of the 500-B in our monster console, this will be printed out and ready at hand. A bit intimidating, though.... I thought I could probably do it by following along until I got to the "Chassis cleaning 2: Clean the potentiometers, rotary switches and switches" part and accompanying graphic. That's where my eyes bugged out and I thought "You touch this and it will never work again. What ARE all these parts/wires, anyway???"

I wish I knew of someone in my neck of the woods who could be hired to do this with as much care as you showed. I'd be one very happy customer!
 
It's just a rats nest in there. You won't be disconnecting anything, just spraying and rotating potentiometers.
Even with factory wiring it's messy.
I just wanted to point out where you spray when you do it. There's an open section or two in each pot you can spray into.
 
I got hold of some of those Dentist files they use for a root canall:tears: and use those to clean the tube sockets.:yes:
 
I've had pretty good results cleaning the inside contacts of RCA jacks with pipe cleaners. I usually fold 'em tightly to get a little extra bulk, and spray 'em with Deoxit before going in. Repeat until they come out clean. Some brands tend to leave lint behind, but that's pretty easy to deal with.
 
Loved the section about waxing the faceplate. Makes the patina absolutely uniform and spotless. Waxed a Yamaha CA-610 II plate today after cleaningper your direction, and it looks like new. Fisher 440T gets waxed next time she's opened up.

Yamaha's lettering is tougher than Mr. Fisher's. Cabinet is infinitely cheaper.

Becoming psychotic for old audio, I am respectfully,
Savory
 
Back
Top Bottom