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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 13th Jan 2007, 11:37 pm   #1
3nf
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Default AR88 Fungus and moisture coating.

Hi
I've just started on an AR88 radio which has a lot of carbon resistors gone high value.
There is a warning notice inside the set saying:
"FUNGUS AND MOISTURE TREATED.
WHEN REPLACING ANY PART OF THIS EQUIPMENT, OR MAKING ANY REPAIRS, THE LEADS MUST BE CLEARED OF ALL COATING MATERIAL BEFORE SOLDERING."

There is no reason given or method suggested for removing said coating.

Does anyone know what the coating is likely to be, and the best way to remove it. I can't actually see any coating, so making sure it has been removed could be a problem.

If the coating is likely to produce toxic fumes, would it be safe to do the work in the open air? (assuming that the soldering iron would work with these gales blowing)?

Any help would be much appreciated.
Thanks.
chris hayes.
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Old 14th Jan 2007, 1:52 pm   #2
Skywave
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Arrow Re: AR88 Fungus and moisture coating.

Hi -

I see you've had little response to your question, so I though I'd throw in my ha'ppeth! I hope it helps.

I am not sure exactly what the treatment is; never seen this notice before on kit of this vintage / heritage.
So what follows is a bit of a guess!

What I have seen is the traditional cloth-covered wire treated with what I believe is a varnish-type coating. It's usually yellow-ish in colour and flaky & cracked.
I've never taken any specific health precautions when working on this type of coated wiring - but there may be others here who will tell me I should!

The comment about "remove the coating" is probably a way of pointing out that if you don't, you're likely to get a dry joint, etc.
As for its removal prior to re-soldering, perhaps methylated spirit would be worth a try.

It seems reasonable to assume that when this coating was applied, servicing at a later date would have been considered - hence the notice . If there was likely to be any serious side effects (fumes, health issues, etc.), I'd expect an appropriate warning notice to be displayed - this set is probably ex-military - and we all know how "exact" such organisations can be!

Good luck with it, anyway!

Al / Skywave
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Old 14th Jan 2007, 4:22 pm   #3
3nf
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Default Re: AR88 Fungus and moisture coating.

Thanks for your comments Skywave.

You are exactly right about the yellowish coating on the cloth covered wire. This wire is still like new. There is a small amount of what looks like pvc sleeving which has become slightly mildew coated, so this may not have been treated. I'll take precautions with the fumes though and do most of the resistor replacements in the shed with the door open. In the past, I've felt quite ill after doing much soldering work on old equipment.

cheers.
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Old 14th Jan 2007, 4:49 pm   #4
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Thumbs up Re: AR88 Fungus and moisture coating.

Ah - Ha!

Now, many years ago I owned a couple of AR88s - one was the "D", one was the "LF". The "D" had the original cloth covered wiring - but hadn't been treated in any way - as far as I could tell. However, the "LF" had undergone a complete re-wire: all PVC wiring - and had been treated with what looked like some sort of varnish coating. (You'd have expected things to be the other way round here - but it wasn't - and besides, that's not the point). Furthermore, this protective coating seemed to everywhere - solder joints, chassis mount components & fixings, etc. (The 4-gang tuning cap. vanes hadn't been "treated" ; )

Health issues. I hear an alarm bell ringing - after your comment about not feeling well after working on old kit. I do know of at least one sad tale of an enthusiast who developed an allergy to the fumes produced from old solder So your suggested precautions seem very wise.
However, right now it's cold outside. Perhaps a good-fitting face mask would be the answer if you need to do the "necessary" indoors.

AR88's - classic comms. RXs; built to last

Al / Skywave
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Old 14th Jan 2007, 9:38 pm   #5
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Default Re: AR88 Fungus and moisture coating.

I would endorse everything Al has said - better be safe than sorry. The coating is likely to be an oil based varnish, and who knows what noxious fumes that can produce.
At work we have to produce equipment to meet some severe military specs. to do with salt spray and fungus growth. The pcbs get sprayed with a polyurethane varnish and if we have to work on them at all Health and Safety regs. say we must use a fume extraction system!
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Old 14th Jan 2007, 10:04 pm   #6
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Thumbs up Re: AR88 Fungus and moisture coating.

Quote:
Originally Posted by Dickie View Post
At work we have to produce equipment to meet some severe military specs. to do with salt spray and fungus growth. The pcbs get sprayed with a polyurethane varnish
In my employment - ditto! You should see what a salty atmosphere does to micro-thin pcb tracks - even after only a few months! The spraying (& subsequent drying) is always done outside - for obvious reasons.

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