The unlock is due to the A7 module.? The problem seems to be in the 300-500 MHz oscillator.? Using the W1 jumper to set it to the low and high frequencies is supposed to give a 300 MHz total range (say, 250-550 MHz) but I get 363 to 529 MHz.? So something's wrong in the oscillator circuit that prevents it from going to the lowest frequencies.? As a test, I tried to set the analyzer to 190 MHz where I would expect the synthesizer to put out 490.250 MHz, and it did, however after a short time it went unlocked again and went up to 529 MHz.? So something additional seems to be wrong.? I checked the internal +12 volt supplies on that board and they are all in spec.? Yikes, might be a hard to find varactor diode.
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I still get a CPU invalid instruction error after a while.? I think I'm going to take a break from the VCO problems and see what I can find in the CPU.? Perhaps a bad ROM which is temperature sensitive?
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Anyone have similar problems with this instrument?
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I can't believe how messed up it is.
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Peter
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