So the REF unlock will be a major problem - you need to fix that before addressing the YTO unlock. Be sure the internal REF (10 MHz) oscillator is on frequency and that the INT/EXT switch is set properly and there as a good BNC connection between the INT and EXT reference BNCs (this assumes you are using the internal reference.
I thought there was an LED for the M/N section (I'll have to check - don't have the cover off an 8566 right now) - or you could post a close up of the REF + M/N modules - As I remember, there is at least one LED there.
The REF unlock is much more likely the problem than any power supply noise.
Cheers!
Bruce
Quoting Jinxie <paul666@...>:
@Bruce
I only had very little time this evening to investigate further, I'm afraid. Not even enough time to try shortening the ground clip lead! I will try out everyone's suggestions in due course, however.
As things stand, I was able to observe that the screen is showing three errors in all now: Battery, YTO Unlock and REF Unlock. I don't recall that last one being there previously. There are three LEDs lit on the stack of modules criss-crossed by the press-on patch leads. I think these are the ones you were referring to:
ON=PLL3 Lock
ON=PLL1 Lock
ON=HET
As I say, all three are lit. Can't see any LED for PLL2, though!
After trying everyone's suggestions I plan to work through the steps suggested in the troubleshooting & diagnostics manual. It's probably going to be above my pay-grade, but nothing to lose by at least trying I guess.
