Re: T912 storage oscilloscope - No 2.7 KV high Voltage


Attilio
 

Greetings to all,
i replaced Q458 but nothing has changed.
I checked the voltage and frequency on the collector of Q458 with the HV diodes CR463 and CR465 disconnected: the frequency is 54 kHz and the voltage around 336 Vpp.
I also measured the voltage + 120V UNREG and it is +151 Vdc; on the collector of Q446 there are 5.3 Vdc, while on the emitter of Q454 there are 5.99 Vdc, the voltage + 8 V is + 7.98 Vdc.
On the output line from the T460 transformer I replaced a 0.1 uF capacitor towards ground but the CR468 diode continues to boil, if I remove the capacitor the diode remains cold and the voltage at - 140 Vdc (instead of -120 Vdc).
If I connect the HV CR463 and / or CR465 diodes there are no - 2.7 KV and the voltages of -120 Vdc and -220 Vdc drop to about - 14 Vdc.

I don't understand where the fault is, maybe it is the T460 transformer that is fault ?

Thanks for the attention

--Cheers
Attilio

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