Jason - I have an answer for you but it gets rejected by your spam filter -
bottom line is that the residual charge after discharge is normal -- Hank
K7HP
----- Original Message -----
From: "Jason Buchanan" <jsb@digistar.com>
To: <amps@contesting.com>
Sent: Sunday, November 13, 2005 1:40 PM
Subject: [Amps] L4 power supply problem?
>
> hi,
>
> I have an L4 with its original power supply. Been working fine for a
> long time.
>
>
> Today, I turn it on and after a few minutes there is a large pop and
> blue spark from near the HV interlock, or located behind the rear tube.
>
> The .82 ohm resistor fried - I replaced it with a new one and carefully
> inspected here and there in the amplifier cabinet. I couldn't find
> anything that burned near the interlock.
>
> I powered it back on in CW low voltage position and the plate voltage
> reads around 1300V. On SSB it reads around 2000V, maybe a little less.
>
> That was all the experimentation I wished to try. I opened the L4-PS
> and looked around but can't find anything on the top side that looks
> burned or stressed.
>
>
> The thing I noticed that was peculiar was that when I powered the L4
> off, the plate voltage would begin to decrease as expected, but then
> ROSE about 200 volts and then slowly decreased again as expected. When
> I took the amplifier cover off there was still a bit of voltage in the
> HV supply, around 150V on the meter. I used a pair of alligator clips
> to ground the cabinet to the top of the plate choke and then removed the
> clips - what was odd was that the voltage rose up to about 100V - when I
> grounded it the meter read 0 again. When I removed the clip it rose to
> about 50V. Finally I put the clip on and left it on and it finally
> stayed at 0 with the clips off.
>
> Has anyone seen this before? Any idea what is wrong... and what I can
> do to repair it?
>
>
> 73 Jason N1SU
>
>
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