[DSP-10] Problems at 19.68 MHz

[Courtney Duncan]

I'm to the point of trying to get my DSP-10 working.

After fooling with L21, I have the 19.68 MHz oscillator tuning that 
range, but the output of the PLL amplifier, U6 pin 6, swings from rail 
to rail whilc tuning C69 very delicately as if the negative feedback 
wasn't working.  All the parts are there and check out as being 
connected and not shorted to anything, however.

Looking at waveforms on the scope, 10X probe, the waveform at the 
junction of C69 and L21 is a nice sine wave, about +/- 5 v.  The output 
of U8 is distorted and the output of U9 is very distorted.  Also, the 
outputs of U8 and U9 are about 1 MHz higher than the oscillator 
frequency.  I don't know how this is possible unless distortion peaks 
are getting counted extra, consistently.  Is this a scope probe artifact 
or a real problem?

In a related, but I think, different problem, I have 10 MHz in (from an 
external source) at U104 pin 1 but nothing is coming out of pin 2. 
Again, there are no obvious shorts in the circuit.  I connected pins 1 
and 2 together to get 10 MHz down to U7 pin 1 input for working on the 
above problem for now.

Anybody have any ideas as to what's wrong here?  Do I have a bunch of 
blown parts?  If so, where's a good place to get replacements?

Courtney, n5bf/6