[Boatanchors] 5+ megohms primary?

[Al Parker]

Hi Steve,
    Do as Doug says to further check it out, but I'm not crazy abt that
15meg with just a lo-voltage ohmmeter.  If some of that resistance to
ground was the line bypass caps (hopefully), maybe you're not too bad off.
Remove them, and put a 60w litebulb under it for a day or 3 to try to dry
any moisture out, before you put any voltage on it, then re-check.
    I use an ohmeter to check things for leakage resistance, but also use
a megger with a variable DC supply, and find much lower resistances when
the voltage gets up a bit, even at 2-300 volts, and something like a BBOD
that looked to be 10-15 megs on the ohmmeter is often down around 1 meg at
400-600vdc.
    Go at it very slowly and don't let the smoke out, once  it does,
you're in for a rewind.
    Sounds like a nice project, but still not those 2x813's ;-)
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info


----- Original Message ----- 
From: <StephenTetorka at cs.com>
To: <boatanchors at mailman.qth.net>
Sent: Thursday, November 11, 2004 11:10 AM
Subject: [Boatanchors] 5+ megohms primary?


> Hi all:
>
> I am presently restoring a AM/CW 6 foot rack rig; 2X1625 in the final.
> Homebrew in 1948 by W2PLY now moving to Senior Residence.
>
> I'm starting my checkout with the 95 pound power supply.
>
> With no power supplied, when using a VTVM from either primary lead to
ground of the main power transformer, I get a reading of 15 megohms with
the SPST in the primary in the OFF position.
> I get 5 meghoms in the ON position - which completes one primary leg
circuit allowing the 115 VAC to primary.
>
> Naturally, I'd expect infinity on this open circuit.
>
> Not much there: terminal screws on the back chassis; hvy AWG to the
switch, a lamp indicator in parallel on the primary amd the xmfr bolted to
the chassis.
>
> I would guess that some insulation somewhere has 'gone old'.
>
> Your generous comments and suggestions most welcomed.
>
> Regards,
> Steve
> WA2TAK
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