Mark,
Thanks for the tip, but I am unsure where the d-c restorer diodes are, but I think you mean CR2352-55 and CR2342-45 and R2356 and R2346, all on the HV board A24?
?? Mark
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-----Original Message-----
From:
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[email protected]> On Behalf Of Mark Vincent via groups.io
Sent: Wednesday, December 11, 2024 2:40 PM
To:
[email protected]Subject: Re: [TekScopes] 7844
Mark
The d-c restorer diodes are bad, replace all of them with 1N4937. Also replace the 22meg 1/4W carbons with Vishay VR37 series, 594-5053DM22M00F. Get 10 of these to replace the 8 in the supply or get enough for both supplies and any other supplies you have. When these go too high, the brightness is high when cold then dims after 15-20 minutes without touching the intensity control. In mine, I recapped the scope and replaced some resistors with higher wattage.
I did put heatsinks on three of the four on each horiz. board. This is because two transistors are close and the heatsinks would not fit on both.
In mine, I did put in BUX48A as replacements for the TO-3s in the power supply. The beta was 1 for three and 2 for the fourth (two scopes). Both were hard to start and would tick several times before starting. After the replacements, instant start without any tick.
Mark
