[Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like Me....

[Bill Carns]

Having worked on high vac systems a lot, I can tell you that a "roughing"
pump (a normal mechanical vacuum pump) will not do a very good job of
getting water out of a transformer....  The usual procedure in a high vac
system, is to rough down to the floor of the roughing pump and then Ion pump
on down to better vacuums. You can see when there is moisture in the system,
as the vacuum will bottom out at a higher level while it "works" on the
moisture.  Getting a water molecule out is much more difficult than getting
out an air molecule.

I would use the roughing pump in combination with some heat, or just the
heat and time alone will do the job..  A roughing pump alone will not help
that much. It sounds like you have the ability to heat the vacuum chamber
and that is good.

Bill

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Thekan, Paul
Sent: Monday, April 01, 2013 9:23 AM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like
Me....

I have a vacuum chamber oven I saved from the dumpster here at work. I
thought I could use it to dry out xfmrs under a partial vacuum. Just need to
find an old Welch vac pump now.

 Anybody see a problem with this...as long as I do not 'implode' anything.

Tnx
Paul
N6FEG

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of J. Forster
Sent: Monday, April 01, 2013 7:09 AM
To: Todd, KA1KAQ
Cc: Military Radio Collectors Association; milsurplus; ARC-5 List
Subject: Re: [Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like
Me....

For years, I've always baked out stuff with non-hermetic magnetics.

I put the thing on a few bricks, put a couple of 100 Watt incandescent lamps
underneath it, and a big cardboard box with some holes in the top over it,
and let it sit for a week or more.

You want the thing to get up to about 130F for several days, at least.
Longer is better, IMO.

YMMV,

-John

==============


> On Mon, Apr 1, 2013 at 12:50 AM, David Stinson <arc5 at ix.netcom.com> wrote:
>
>>
>>
>> I thought about putting the whole thing sans end bells into a 
>> 200-degree oven for a couple of  hours to dry it out
>>
>
> This is  a problem with big chunks of iron in old transmitters, too. 
> Many do not realize how similar to a sponge the laminations and windings
are.
> And old transformer left sitting in a damp cellar or storage shed is 
> an accident waiting to happen if you just haul it out, hook it up, and 
> apply voltage. Might happen in 5 seconds, 5 hours, or 5 days, 9.9999 
> times out of
> 10 it'll zorch.
>
> The oven works great as is provides a means of getting rid of the 
> moisture without introducing more. On bigger pieces it can take a day 
> or two, maybe more, to feel safe enough to put power to it. And 
> there's never a guarantee, of course. But recovery rate is far, far 
> better when dried out than when not. The trick is to heat it up long 
> enough for the heat to reach the core and drive out the moisture. It's 
> all about the mass. Smaller = faster; hours vs days.
>
>
> A good reminder as many of my dynamotors are out in the garage here in 
> humid NC. Though lately humidity has been amazingly low.
>
> ~ Todd,  KA1KAQ/4
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