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Author Topic: CLEANING UP VARIABLE CAPS IN DIRTY OLD AMPLIFIERS?  (Read 2315 times)
WB4SPT
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« Reply #15 on: February 09, 2019, 10:42:12 AM »

You want to keep aqueous ammonia away from bare copper, though, correct?
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W9IQ
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« Reply #16 on: February 09, 2019, 10:59:32 AM »

You want to keep aqueous ammonia away from bare copper, though, correct?

Correct. Stoichiometric quantities of aqueous ammonia will react with copper, zinc, and brass.

In the case of copper, initially copper hydroxide will form as indicated by a light blue color. Further reaction with the ammonia solution will cause deep blue ammoniacal copper solution to form.

- Glenn W9IQ
« Last Edit: February 09, 2019, 11:10:55 AM by W9IQ » Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
N6QWP
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« Reply #17 on: February 09, 2019, 01:36:14 PM »

Thanx for the heads up on using ammonia.  Will seek another venue.  The band coil would be vulnerable......as would the large choke and some wiring.

Guess I am back to KrudKutter and perhaps rubbing alcohol or carb spray to flush?

Does carburetor cleaner spray leave any kind of residue???  What about starting fluid?  (Both are cheap).
« Last Edit: February 09, 2019, 01:41:14 PM by N6QWP » Logged
AC5UP
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« Reply #18 on: February 09, 2019, 02:16:36 PM »

Does carburetor cleaner spray leave any kind of residue???  What about starting fluid?  (Both are cheap).

Carburetor cleaner may leave a slightly oily residue as it does contain petroleum distillates but nothing heavy enough to attract dust.  About the same as WD-40 after being wiped off, which does dry completely over time.  Read the label on starting fluid and I think you'll find it's mostly denatured alcohol.  If so, you can get a better price per ounce at the local big box hardware store in the paint section.  Quart can.

Which makes me wonder if turpentine might be worthwhile as a chassis cleaner...
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G3RZP
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« Reply #19 on: February 11, 2019, 04:37:30 AM »

Can you get genuine turpentine in the US? Over here, it's all an artificial 'turps substitute'.
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LA9XNA
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« Reply #20 on: February 11, 2019, 01:00:21 PM »

For chassis components and mechanical bits try washing  with hot water and wash-up liquid.
This will remove all grease on the parts.
In case you have an old dish washer not in use, spray the parts in a mix of water and wash-up liquid (mix 1-10) and let it soak for 5-10 minutes.
Stick it in the dish-washer on low temp and short time program. Be sure to dry it properly with an air nossle and hair dryer/heat gun, but be aware of the temperarure on painted componets because heat can damage the paint.

For smaller mechanical parts like switches and variable capacitors you can use an ultrasonic cleaner with water and wash-up liquid until all the dirt is gone.

After the parts are cleaned, rinse off the part in fresh water and use a compressed air nossle to remove most of the water.
Then empry the tray on the ultrasonic and use alcohole (NO HEATER ON THE ULTRASONIC) And let the part sit for a few minutes.
The alcohole will remove the water from the part even in the small cracks.

Oil moving parts as required for good operations.
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N0MKC
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« Reply #21 on: February 11, 2019, 02:54:30 PM »

So far as drying it out after cleaning...   

Hair dryer?  Somewhat labor-intensive, but should speed the drying process quite a bit, and no need to wait for warm, sunny weather.

(I'm kinda surprised it hasn't been mentioned yet...)
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N3DT
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« Reply #22 on: February 11, 2019, 02:56:12 PM »

Forget about the carb cleaner, starting fluid or similar products. They're far too risky on non-metallic parts. WD40 is not bad, it eventually evaporates and can be cleaned up with alcohol. But WD40 will also remove a lot of inked data, so be very careful where you put it. I doubt there's any magic solution. I like the ammonia but would also be careful where to use it and would wash it off also with alcohol/distilled water. No matter what you use, there is going to be some amount of care involved with brushes and rags. Distilled water wash is not bad, but does not remove a lot of grime and may also get into things. Need compressed air or heat to remove it, consider even careful use of a heat gun or hair dryer. WD40 on a rag or brush is my favorite followed by denatured alcohol and some sort of compressed air. Some small shop type vacs can be reversed and are not too brutal. I have a small $25 reversible shop vac that's about ideal for blowing not stiff air and I use it to blow out my computers too.
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N4NYY
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« Reply #23 on: February 11, 2019, 04:23:29 PM »

Seeking input on what to use on another old amplifier (Collins 30L-1) that is very dirty.  Have used KrudKutter in the past, but found that the variable capacitors seemed to discolor and even corrode somewhat over time after having been sprayed, rinsed and dried.

While the KrudKutter worked very well on most of the amps and other radios, wondering if there is a better spray of some kind that does not require rinsing with water when finished-especially for the caps....OR....a product to follow up with (immediately afterwards)?

Since there is high voltage and the risk of arcing on the variable caps in an amplifier, I would like to find a proven product that will rid the surfaces of any crud, nicotine and anything else that contaminates....and hopefully leaves them as new.

Something that could follow the normal use of KrudKutter and rinse (to eliminate the problems of air and water on the plates) would probably be ideal.....as when first cleaned with the KrudKutter, the results seem great.  

This time of year, it is very difficult to properly dry out a rig that has been rinsed with water.  No hot sunny days to help.

Automotive sprays, or electronic sprays (by name)?

I have used the Krud Kutter and I was one of the first to champion it here for restorations. I have used it on variable caps, but only on radios and it worked great. One of the few products that gets rid of all the nicotine. Saying that, I have never used it on an amp and the voltages associated with it.

If I have done it in winter, I would blow it out with a compressor and park it over a hot air heating vent for a day or 2.
« Last Edit: February 11, 2019, 04:26:29 PM by N4NYY » Logged
N6QWP
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« Reply #24 on: February 11, 2019, 05:24:59 PM »

Well, being bored today, I decided to take a chance and try to clean up this old 30L-1 amp using KrudKutter and boiling water and CRC QD Contact Cleaner....before the upcoming storm hits.

While cold (50's), the KrudKutter did dislodge all kinds of dirt.  Flushed it with boiling (almost) water.  After a while, (I could see the surfaces were getting that "salty finish"), I took amp back outside and hit the caps with CRC QD Contact Cleaner.

Looks like I will have to scrub any surface that I want to shine.  The spray is not supposed to leave any residue, but the surfaces showed a distinct dull finish....that if I took my finger, I could remove......this on all the areas of the variable caps and elsewhere on some of the chassis and obvious (previously) shiny surfaces.

I guess that there is no way, short of hitting all of the surfaces with some kind of rubbing action, I will be able to get anything like a new finish.

The question now, is whether there will be any tendency to arc between these oxidized surfaces at high voltage under hi power (500-700 watts).

I have noticed this effect on four different 30L-1 amps after the flushings.  Have only had a flashover on one of them so far.....but believe that was due to a faulty tube.  Time will tell.

Would like to hear from anyone who has tried cleaning similar amps using similar products.

Amp is presently in front a 1500 watt heater, getting a good drying out.  I might have to go back and hit everything again.....the surfaces on the white porcelain high voltage cap and some insulators still are not totally clean.  Will decide later.....and do it on a warmer day, if necessary.

« Last Edit: February 11, 2019, 05:45:48 PM by N6QWP » Logged
N4NYY
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« Reply #25 on: February 11, 2019, 06:14:43 PM »

I have not had that "salty" residue on the variable caps that I did. They came out looking new.

However, it interacted with some metals. I would see this effect on screws or some chassis. But I never had it happen on variable caps.

The only other issue I had was on silkscreen paint over shiny aluminum. The paint just came right off. It did not affect painted steel or silkscreening over painted surfaces. It works great on plastic.

BTW, when I used Krud Kutter, I only leave it on for about 1-2 min, then flushed it with cool water. I never used boiling water.
« Last Edit: February 11, 2019, 06:18:33 PM by N4NYY » Logged
N4NYY
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« Reply #26 on: February 11, 2019, 06:28:50 PM »

I did some quick googling and the white power may be Cadmium Oxide. It appears to be toxic and common on old equipment (I'm not familiar with it). Depending on where you google, they will tell you to stay the hell away, or not to worry about it. There were several methods to cleaning it, but I will leave that to the experts. I would take precautions just to be safe.
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N6QWP
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« Reply #27 on: February 13, 2019, 09:11:36 AM »

After looking up cadmium oxide, it seemed that it would be brown in color.....not the powdery white or gray.  It appears to be simple oxidation....or residue from the water or spray on certain surfaces?

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N4NYY
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« Reply #28 on: February 13, 2019, 03:25:32 PM »

After looking up cadmium oxide, it seemed that it would be brown in color.....not the powdery white or gray.  It appears to be simple oxidation....or residue from the water or spray on certain surfaces?



Try some naval jelly on a spot and after like 30 sec, rinse it off. If that works, use it. I have used naval jelly on chassis oxidation, but never a variable cap.
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N6QWP
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« Reply #29 on: February 14, 2019, 09:46:02 AM »

Thanx I'll give that a try when the storms finish up here.
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