I have a HP201C oscillator, which mostly works. But, on the one freq range that I need (x1), the output dies after a short period. This sometimes takes just seconds, sometimes a few minutes. Other freq ranges are OK. A couple of questions:
I have a schematic.
TIA, George
OK. Rmv the screws in the back, slide guts forward.
Opening it doesn't lead to an immediate soln to (1). There is no black part.
George
Hi George,
Your oscillation stops, because the loop gain drops off. Similar HP generators (the 200, that I have) do have a potentiometer that adjusts the amplification, and hence the loop gain. Your generator just might need a little bit of adjustment. If you have the manual, it describes how to adjust that properly. Another problem that you might have is the aging of the paper and electrolytic capacitors in the circuits. The fact that the oscillation stops at the lowest frequency, might indicate this. In this case you just need to recap the instrument ;-)
Good luck, Peter
George wrote:
that
It turned out to be a bad tube. The grid on the 6AU6 developed a soft short (<
1M) to the cathode when it got hot. This was enough to kill the loop gain on the x1 range, where the bridge resistors were 8.3M, but didn't disrupt the other ranges, where the bridge resistors were smaller.George
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