Re: 7B50 - No SweepCR262

Mark Vincent


Nothing stands out yet what is the problem. Start checking d-c voltages. Something will be off. This is what I would do. I see R313 is to a switched voltage. See if you get the -15V on one end of that resistor. This is a point to check. Sometimes writing down voltages to compare has to be done when enough numbers are needed. There may be someone else in this group that may have had the same problem and can tell you what that problem was.

The 741 in the scope would have been the first thing I would have put in to see if that was the problem. I have had this number give problems in the past. The string(s) of resistor(s) can be checked to see if they are too far out of tolerance. I know it is unlikely, check the 470,000 ohm resistor on the input with the IC out. The inverter control and B+ adjust pots affect each other. You may have said what the voltages at the + and - inputs are. They should be almost zero. That IC gives the appearance of a transconductance circuit by the two resistors from the output to ground. I not stating this is the type of circuit, only looking similar. I have no other ideas of the two problems you have. Further information from you will help.


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