Like RNMarsh says, the board is easy to get to. Once the top and bottom are removed, there is access to both sides.
Does the oscillator clip on all frequency ranges and settings or only certain ones? If it is all, then I would suspect a failure in the amplitude control circuit. If only some frequencies clip, then maybe just a tweak of the adjustment is required.
I'd use solder wick to remove the old chip if you decide to do that. These boards are pretty easy to work on. Not like some cheap boards that lift a trace as soon as you touch an iron to them.
Is the output of the oscillator (at TP1) swinging more than +10V , -10V? What is the voltage at TP8 (the gate of the control FET)? If I remember right, a larger output signal should cause the voltage at TP8 to go lower in voltage, turning on the FET and reducing the oscillator gain.
If you adjust the gain pot (R30), you should see the voltage at TP8 swing from high to low voltage. If it does that, then it is likely a bad FET. If not, then look back towards U2A, B, C.
Of course the frequency switches must be working to switch in the proper range caps.
Terry
Does the oscillator clip on all frequency ranges and settings or only certain ones? If it is all, then I would suspect a failure in the amplitude control circuit. If only some frequencies clip, then maybe just a tweak of the adjustment is required.
I'd use solder wick to remove the old chip if you decide to do that. These boards are pretty easy to work on. Not like some cheap boards that lift a trace as soon as you touch an iron to them.
Is the output of the oscillator (at TP1) swinging more than +10V , -10V? What is the voltage at TP8 (the gate of the control FET)? If I remember right, a larger output signal should cause the voltage at TP8 to go lower in voltage, turning on the FET and reducing the oscillator gain.
If you adjust the gain pot (R30), you should see the voltage at TP8 swing from high to low voltage. If it does that, then it is likely a bad FET. If not, then look back towards U2A, B, C.
Of course the frequency switches must be working to switch in the proper range caps.
Terry
TerrySt and RNMarsh,
Success! Replaced U2 with socket and new chip, and it works perfectly now! I've put up with that problem for several years believing that I would have to remove the circuit board thereby creating more problems for myself than I was trying to fix, but did it with solder wick, in about 1-1/2 hours. I truly appreciate your taking the time to give me a hand on this!
Best regards,
Wade
Success! Replaced U2 with socket and new chip, and it works perfectly now! I've put up with that problem for several years believing that I would have to remove the circuit board thereby creating more problems for myself than I was trying to fix, but did it with solder wick, in about 1-1/2 hours. I truly appreciate your taking the time to give me a hand on this!
Best regards,
Wade
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.