Hi Jared,
One of my 5065's have exactly this fault.
One approach is to rebuild with a new power inverter. Another is to
rebuild the amplifier board so it does not need -20 V and can operate
only on +20 V.
There should be DC-DC inverters, but I failed to grab a suitable
pre-built board for it.
I would enjoy not having to hear the 3.5 kHz switching frequency in my lab.
Cheers,
Magnus
Den 2021-12-02 kl. 15:15, skrev Jared Cabot via time-nuts:
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.
_______________________________________________
time-nuts mailing list -- [email protected] -- To unsubscribe send an
email to [email protected]
To unsubscribe, go to and follow the instructions there.
