Re: FG 504 Offset problem

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Tom Miller <tmiller@...> #51909 Do you have the +/- 25 volts? What is on pin 2 of the amp? Can you set that to 0 volts with R1140? The +7 at pin 6 sounds bad if pin 2 is near 0 volts. What about Q1160 and 1180. Are they ok? Check R1160 and 1180. Regards, Tom toggle quoted message Show quoted text ----- Original Message ----- From: gehp01 To: TekScopes@... Sent: Saturday, August 28, 2010 5:16 PM Subject: [TekScopes] FG 504 Offset problem Dear All, The positive side of the DC offset of my FG-504 is not working, but negative is working fine. I thought this would be an easy fix, but I am about to quit. In case someone gets interested, I have uploaded this section of the schematics. First, I checked the + and - 15V and the +/- 4V input and they are ok. Next, I pulled out Q-1150 and Q-1170 and, to my surprize, both are ok also. With these transistors out of circuit, the output of U-1145 goes from -13V to + 7.0V. I ran out of ideas. I would not venture to replace U1145 since this would mean to disassemble almost the entire unit. Any suggestions? Thank you
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