>Serial number 4017.
>
>Symptom: When A/C power switch is turned on, plate current is 325 MA and
>does not go to zero.
>
Bee - -
*? Sounds like maybe a grid/filament shorted (0v bias) tube. Typically,
the short only occurs when the filament is hot/expanded. Thus, an
ohm-meter check on a cold tube will not detect the problem.
>Plate voltage is normal at 3200 volts DC. Grid current meter goes
>negative; pinned to left side of meter. Do not use QSK.
>
>Troubleshooting thus far: Disconnected B+ line at power supply board.
>Power supply is OK. Substituted two other known good 3-500Z tubes; tubes
>are OK.
** Do the two other tubes draw 300+mA anode/plate current on standby?
>
>Measures 5.79 rather than 5.0 filament volts (T1).
** Measured at the socket pins or at the xfmr?
> Caps C24, C25, C22,
>C23 and C28 check OK.
>
>Should D2 the 1N3308 Zener Diode be suspect? This component seems
>difficult to check.
** A simple ohm-meter check will reveal if the zener is shorted in both
directions.
>
>Request help to troubleshoot the above described symptom.
>
>Thanks,
>
>Bee, K4JLD
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