[time-nuts] PRS10 schematic or part identification help

Nathaniel Bezanson myself at telcodata.us
Mon Dec 31 08:36:13 UTC 2012

Charles P. Steinmetz  wrote:
> For schematics, see <http://www.ko4bb.com/manuals/>.  Search for "prs10".

Aha, I don't know why I didn't see that when I searched around. Bookmarked! The response from this list, to a newbie with a probably-obvious problem, is incredibly helpful and welcoming. Thank you all!

cdelect at juno.com wrote:
> It is indeed C900, I looked into a lamp assy. I had on hand and the silk
> screen is clearly marked.

Cool, thanks. The old one was easy to remove, as the body crumbled and I could desolder the leads one at a time. Getting the new one in took a moment longer, as I had to cut an angle on the tip of my solder-sucker to get in there and clear the holes. Then it went in without much fuss, thankfully sparing me from having to remove the board.

> That attached PIX shows green corrosion on a folded metal plate connected
> to the power resistor lead.

Mine appears to be a different revision as it lacks that plate, and there's no corrosion that I can see, merely some tantalum spoo and general evidence of high-temperature operation. I didn't attempt to clean the residue off, as I don't know the lamp envelope material, and am hesitant to hit it with random solvents.

I put it all back together and powered it up with the cover off, and after the lamp values stabilized, I could see a faint glow through the peephole. Success! Sort of. I reinstalled the cover and it's been sitting a little over three hours now, but won't lock.

RbMon shows that AD9, "Photocell I/V" is low, hovering around 0.157, and the DS "detected signal" values are low -- error signal wanders between -26 and +30, and the resonance signal never gets above 11. (Manual gives 800 as an example "strong" resonance.) I'm not sure where to go from here, so further input is most welcome.

The photo I/V signal is available on an external board with just the outer cover removed. I could take a peek with a scope, but I'm not sure what I'm looking for. I've been letting it run with the cover installed, figuring that stray light through the peephole (especially modulated light from ye olde fluorescent fixtures) might interfere.

Thanks and goodnight! :)

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