[Milsurplus] VR tube question

[jmfranke]

Probably not three bad regulators.  The 0A2 has multiple connections to the 
cathode and anode.  It appears pin 1 is being used as the high voltage 
input.  Pins 1 and 5 are both tied to the anode.  The load is probably 
connected to pin 5.  With the 0A2 out of the socket, and no power applied, 
measure the resistance to ground from pin 5.  I think you have a short to 
ground from pin 5. If the resistance measures higher than a couple thousand 
Ohms, you may have a capacitor that only breaks down when the voltage is 
above a certain point.  If so, I would remove the 0A2 and connect a 
milliammeter between pins 1 and 5 and apply power.  If the current is 
excessive, look for the breakdown point.

John  WA4WDL

--------------------------------------------------
From: "Robert Goff" <robert.h.goff at gmail.com>
Sent: Wednesday, September 15, 2010 2:58 PM
To: <milsurplus at mailman.qth.net>
Subject: [Milsurplus] VR tube question

> Greetings to the list.  I'm hoping someone can help me-I'm a pretty
> inexperienced serviceman.
>
> I've been working this morning on a T-195 with (apparently) no MO
> output.  I've traced the problem back to the voltage regulator module
> next to the PTO.
>
> Checking at the MO plug I had no +150V regulated.  I checked the
> limiting resistor which is 3K-just like it's supposed to be. But, when
> I replaced the OA2 with 2 others I had, there was no change-still no
> 150V.
>
> When I pull the regulator tube I have 250 volts at pin 1, with the
> tubes in this drops to nothing.
>
> Is this just a case of three bad 0A2s?
>
> Help!
> Robert
> W7MKA
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