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Old 5th Jun 2019, 8:06 pm   #68
OldTechFan96
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Join Date: Jul 2017
Location: Newcastle Upon Tyne, Tyne & Wear, UK.
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Default Re: Hameg HM307-3 Cleaning and Repair

I've installed the new 741 op amp, socket and tried both new transistors. The -1000V rail is still too low!

With BD232:

-1000V rail: ranges from -960V --760V.

C of T301: 400V

Input V of pin 2: 0V

Input V of pin 3: 0V

Output V of pin 6: -5.3V.

With BF259:

-1000V rail: ranges from -960V --760V.

C of T301: 310V

Input V of pin 2: 0V

Input V of pin 3: 0.65V

Output V of pin 6: -5.3V.

What should the voltage be at the inputs of the IC?

Does anybody wonder if something connected to the -1000V rail is pulling it down?

I'm going to lift one end of R305 and see what I measure.

Last edited by OldTechFan96; 5th Jun 2019 at 8:07 pm. Reason: More info
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