[time-nuts] Re: HP 5065A, no 2nd harmonic.

[Jared Cabot]

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 <jaredcabot at protonmail.com> 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 time-nuts at lists.febo.com 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 time-nuts at lists.febo.com 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 -- time-nuts at lists.febo.com -- To unsubscribe send an email to time-nuts-leave at lists.febo.com
> > 

> > > To unsubscribe, go to and follow the instructions there._______________________________________________
> > 

> > time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send an email to time-nuts-leave at lists.febo.com
> > 

> > To unsubscribe, go to and follow the instructions there.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: A15PowerSupplyandRegulatorAssemblySchematic.png
Type: image/png
Size: 119079 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20211202/2cdbb56a/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 855 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20211202/2cdbb56a/attachment.sig>