[Test-Equipment] Looking for HP quartz oscillator schematic

[Carl Walker]

I was fortunate enough to receive an email from a list member with the same 
type oscillator, with the component values for the ones I had questioned 
(thanks again, Will). Unfortunately, these toasty components appear to be 
from the 5 MHz distribution side of things (I've replaced them, and the 
outputs look nice and stable). 

The oven side of things still seems to be malfunctioning (that controller is 
underneath the opposite end-cap of the oven housing). There are indeed two 
thermo-fuses located there, but they are both OK. I'll have to spend a bit 
more time probing around in there to try and make a determination as to 
what's going on - but I've got to say that HP made these things a real bear 
to work on. There's just not enough lead length to be able to pull boards out 
far enough to figure out what's going on without disconnecting a number of 
wires. It's quite understandable why it's built that way, but it's just not 
friendly to have to repair in the field (as I'm certain was never intended).

I was really hoping it was a thermo-fuse issue - that's what seems to be the 
normal failure mode for the more modern 10511 and 10811 series oscillators.

I'll do some more examination of the oven and controller in an attempt to 
make it operational once again - but the really good news was that Will had 
an extra one of these units he was willing to part with. Hopefully that will 
solve the problem on the larger scale of making the equipment operational 
again, but I still would like to repair this defective unit if at all 
possible - these are quite good performing oscillators, and I'd hate to just 
have to throw the assembly into the salvage bin.

-Carl, WA1RAJ