[Chris Wilson]

Wow, great info and analysis, thanks you two! I did manage an hour and a half on it early yesterday, and followed the set up routine for A22 in the manual. Nothing was a mile out save R39. That was out and is also very touchy to get the frequency right from the rear BNC. Not touchy as in noisy or scratchy, touchy as in a tiny amount of turn gives a big shift in frequency. More than I would have said was good design practice. Again this comes back to something in that circuit perhaps having changed? A quick squirt of freeze spray seems to send things a bit daft, too in that area, but hard to say which particular component without a riser board.

After setting up as per the manual it did seem better behaved, but the jitter still returned, and just twice, some spikes.

David: C17 measured fine, out of circuit. 0 Ohms ESR

I also checked all the matt black 0.01% resistors, in circuit, and they showed no obvious value deviation, hot or cold. I am glad you mentioned part numbers, the HP parts list has big gaps where only a HP number is given for some transistors. Is there much chance some are unobtainable?

My gut feeling is there is something "downstream" putting spikes on things, it looks to me, (but what the hell do I know, it's just a *feeling*) too many test points have these seemingly random spikes. They seem so fast as well, just like the spikes on the display. Whilst the jitter seems fairly slow. One tiny clue is if I let it do a self calibration it's common for me to see the spikes straight after....




Jeremy: Should I be probing with the probe at X1 or X10? Nearly all shots are at X10. I don't want to be skewing things with bad measurement practices.



I left it running last night, and will have a look at it in a bit.

I will re-do the scope patterns and post a screen shot. I'll also try with my USB scope, which I now have back after lending it someone for a day, two months ago!

I see the traces in the schematic have a slightly flat top to them, is that significant? Mine re pointed...

Thanks for your patience and fabulous support, this is by far the most complex thing I have ever had to fiddle with.