Jared, I think an -20 V rail short to ground has first blowup A15Q10. Then the -20V converter was light loaded and the output DC voltage goes up and blows also the zeners. The most easy way to protect and repair: replace A15Q10 with a LM337 with 2 resistors to adjust the output to -20V. Remove the blown zeners and diode and mount the 2 resistors on the removed zener positions.
Regards, Henk On Thursday, December 02, 2021 15:15 CET, Jared Cabot via time-nuts <[email protected]> wrote: > So it looks like I lost the -20V rail. Seems that A15Q10 (2N4234), A10CR9A > (9V Zener), and A15CR9B (11V Zener) are all dead for some reason. > Q10 is easy enought o find, but the zeners are a little more tricky, they are > specified as part number 1902-0247, a 20V, 1%, 0.4W +0.005%TC zener (20V made > up of the 9v + 11V). > I can find a 5% 9V (1N936A), but the 11V is harder to find. > > Maybe I should look into redesigning this board entirely, the transformer on > mine is rather noisy anyway..... > > Schematics attached for reference. > > > > Jared > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > > On Thursday, December 2nd, 2021 at 21:04, Jared Cabot > <[email protected]> wrote: > > > Latest update. > > > > Looks like I'm getting 2.76VDC out of A7J1 and I can't adjust it with A7R3. > > According to the manual, it should be less than 50mV.. I was able to set > > this to around 0.5mV previously, so it did work at one point. > > > > Q1 and Q2 test ok on my ebay component tester, IC1 is a selected uA741TC, > > but I'm not sure how to effectively test it. > > > > (I attached the schematic, hopefully it shows up ok). > > > > Jared > > > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > > > > On Thursday, December 2nd, 2021 at 18:57, Jared Cabot via time-nuts > > [email protected] wrote: > > > > > Well, it seems more digging is needed... I have 84uA Photo I coming from > > > the RVFR on A7P1, but the front panel is at 14 (Should be 42 for my Photo > > > I level) > > > > > > Manual says look at Q1, Q2 and IC1 circuits. Anyone have any pointers or > > > suggestions on what to check? > > > > > > Jared. > > > > > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > > > > > > On Thursday, December 2nd, 2021 at 17:21, Andy Gardner, ZL3AG via > > > time-nuts [email protected] wrote: > > > > > > > Don't give up now, Jared! You must be so close to getting that puppy > > > > running correctly. > > > > > > > On 2/12/21 9:16 pm, Jared Cabot via time-nuts wrote: > > > > > > > > Well, yay... > > > > > > > > I put the OCXO back in the 5065A, and got a good 2nd Harmonic > > > > > reading. So I started going through the alignment procedures and > > > > > somehow I now have no 2nd harmonic again, and I can't get it back... > > > > > > > > I'm starting to lose interest in this thing, seeing as I have the Leo > > > > > Bodnar GPS standard anyway that I don't have to sit for hours > > > > > twiddling dials and poking things just to get it maybe sort of > > > > > working. > > > > > > > > I might give this one more chance before I sell it off to someone > > > > > with a little more patience, or who prefers fixing gear instead of > > > > > actually using it. I think I've had this thing working for all of a > > > > > couple days in the months I've owned it, whereas the GPS standard is > > > > > the size of a pack of cards and has never failed in the same time. > > > > > > > > Jared. > > > > > > > time-nuts mailing list -- [email protected] -- To unsubscribe > > > > send an email to [email protected] > > > > > > > To unsubscribe, go to and follow the instructions > > > > there._______________________________________________ > > > > > > time-nuts mailing list -- [email protected] -- To unsubscribe send > > > an email to [email protected] > > > > > > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
