There is a possibility that the arc (either from the RF deck/tubes or
in the wiring/connections) took out something in your power supply
now.
You probably should check each of the series electrolytics, diodes
and the resistors across the caps, with a ohmmeter and hi pot the
caps with a small (450 V) power supply to check leakage, that it is
uniform for all of them. You might discover some crud leaking out of
on or more caps too. You can upgrade that power supply to modern
electrolytics (same uF in smaller cans) or try to reform your 'lytics
after testing them, using the same high voltage power supply. Check
the forward conduction for each diode too, using a power supply and
series R, or a battery that can turn them on, with a series R.
While at it, check the 3-500Zs with the high potter, now that there
has been an arc somewhere.
73
John
K5PRO
>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.
>73 Jason N1SU
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