Wax Capacitor - Bush TR90C (208)

[Micker]

Can I query what other people use to try and clean up wax capacitor exteriors in an attempt to read them without destroying the printing? This set has One but is impossible to read the values though one can vaguely make out some script. I have taken a couple of digital pics but they are nearly as hard to see anything. I do have the trader sheet - No. 1554 with the schematics but they bear no relation to what I can actually see' after removing the chassis from the case even though the internals look to be all original. There appear to be caps/resistors in places where none are shown and vice versa, with values given that are nowhere what the trader sheets states. I'm presuming BUSH knew what they were doing in the first place so trying to replace like with like.

[ppppenguin]

I tend to run a fingernail through the wax to scrape some off. Not the pleasantest of things to do but it seems to work well enough.

At these low voltages, even a leaky waxy will probably be good enough except in a few sensitive places like AGC lines. Though this set uses an 8uF electrolytic on the AGC.

I'd replace all the electrolytics. Values aren't critical. 10u will repalce 8u. 22u or even 47u will repalce 25u etc. The only one that might make me pause is C22, 4u. I'd probably find a 4u7 rather than just stick in 10u as it could be regulating the bass response. I'd also replace the waxies even though I know in my heart that it's almost certainly not necessary.

[Micker]

cheers for that, most appreciated and I will be doing just that - once again cheers.

[Beardyman]

Should the finger nail technique not work due to the wax hardening, I find that applying a little heat from a hair dryer or even a soldering iron (not touching it of course, the stuff absolutely stinks!) can help. Usually the dust & top layer of opaque wax slide off, can be messy but worth a try if all else fails.

[Micker]

well - I managed to balls that up completely ! however I did take a pic before I did and one after I have managed to remove all identifying script. Is there a way I can add pics to see if anyone might be able to identify it visually?

[ppppenguin]

I though there was a sticky about adding pictures here: http://golbornevintageradio.co.uk/forum/...php?fid=21 but I can't see it at the moment. Quick guide:

1: Click "reply to this topic" rather than use "quick reply". If you're already using quick reply then click "preview post" to see full range of controls.

2: At bottom of page you will see "New attachment Browse". Select the file you want to attach.

3: This is the bit that has caught many of us first time round: Cliick "add attachment"

4: Repeat as required.

Hope you like my test image. Taken some years ago in the stores of the Brimingham Science Museum.

[Micker]

thanks Jeffrey - I'll try that later when I get back - that cat looks very dead btw...

[westcliff]

I usually clean dirty wax capacitors with WD40 aquirted onto a bit of kitchen roll.

Gus.

[Micker]

As you can see from first 'uncleaned' pic there is some barely decipherable script, then the following two (one each side) after what I thought to be a gentle rub, left with nothing!

[ppppenguin]

Those are not what we usually call waxies. They're silver-mica, typically below 1000pF, and almost certain to be OK. Depending on value, the usual replacements would be polystyrene or particular types of ceramic (C0G or NP0). By removing and replacing them you may have upset alignment.

The classic waxies are tubular, paper dielectric, 1000pF up to 1uF, and almost guaranteed to be faulty.

It would help to have some photos of the inside of your radio.

The cat may just be resting