Quote:
Originally Posted by OldTechFan96
I replaced R310 last week because it had drifted a bit high. I have replaced it again and we are back in business! The -1000V rail is now what it should be. You were both correct about the HV breakdown.
This shows that the new BF232 and op amp are working correctly.
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That’s good to hear. You mention that you had already replaced the resistor and it was this replacement that failed? If you have replaced this with another from the same batch, then bear in mind that although the current running through it is quite small, the composition of the replacement may not have been suitable for handling the voltage across it, in which case the second replacement could fail again in a similar manner. My estimate suggests that the voltage across it should be in the order of 215v and you would want a comfortable margin, so maybe one rated for 350v or higher.
Quote:
Originally Posted by OldTechFan96
If I remember correctly, the last thing I did before the PSU fault was replace a zener in the CRT section. We were also investigating the lack of brightness of the CRT.
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Yes, how is that looking now?