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

[Jared Cabot]

Hi,
I have performed the test with the 10Mohm resistor.
With an 0.5V P-P signal from the function generator into A7J1, I get 980mV at A7TP2 (Manual says it should be about 0.9V)
When I probe the A7 output (Yellow wire) i get a good output as described in the manual too, so it looks like my A7 module is ok.

However, when I plug the RVFR back into A7J1, I get exactly no output from the A7 module at all.

Interestingly, the highest I can get the OCXO to adjust using the coarse adjustment (with the fine adjustment set to 250) is
4.99996155 MHz, measured using my GPS referenced 5335A connected directly to P3 on the A10A2 OCXO Frequency Divider/Amplifier Assembly.

If this isn't close enough to exactly 5MHz, could it be causing a problem?


Thanks,
Jared


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Saturday, November 27th, 2021 at 01:24, paul swed <paulswedb at gmail.com> wrote:

> Jared
> 

> I took a look at the manual and if you inject 137 hz at .5 Vpp through a 10
> Mohm R thats in a sheild into A7j1 you will see .9 Vpp at TP2 and some
> large signal upto 16 Vpp at Yellow out. That would say the A7 module is
> good. It looks like the 2 ICs are lm741 class opamps if they happened to be
> bad.
> 

> Regards
> 

> Paul
> 

> WB8TSL
> 

> On Wed, Nov 24, 2021 at 8:36 AM Jared Cabot via time-nuts <
> 

> time-nuts at lists.febo.com> wrote:
> 

> > Hi,
> > 

> > Ok, I managed to get a moment to do a few tests. I'll try to answer the
> > 

> > questions so far, sorry if I miss something out.
> > 

> > For test equipment, I have the following gear of possible use:
> > 

> > -   HP 5335A 200MHz Universal Counter with 1.3GHz option
> > -   Leo Bodnar GPS Reference
> > -   HP 34461A Multimeter, just calibrated.
> > -   Tek TDS748C 1GHz Scope
> > -   Multiple HP E361xA Power supplies
> > -   3325A Function Gen (All options)
> > -   Many other bits of gear too, including a billion TM500 modules and
> >     

> >     mainframes etc.
> > 

> > On the 5065A front, I have replaced the resistors in the RVFR with
> > 

> > Mil-spec Vishay RN55, RN60 and RN65 series parts, cleaned the glass
> > 

> > elements and added a 100 deg.C thermostat to prevent over temperature
> > 

> > events.
> > 

> > I have replaced all the wet tantalum capacitors in the entire unit with
> > 

> > United Chemicon KYB 220uF, 63V capacitors (10,000 hour rated), bypassed
> > 

> > with C0G/NP0 0.1uF MLCC ceramic caps, there was no PCB damage, but two tant
> > 

> > caps had just started leaking, luckily not reaching the PCB's.
> > 

> > I added heat sinks to the two diodes on the A2 board and replaced the RIFA
> > 

> > mains filter cap too. The 3 big mains filter capacitors tested well within
> > 

> > spec, with leakage down around 10uA.
> > 

> > -   On A8 Pin9, I get 137KHz, 174mV P-P
> >     

> > -   A7 TP2 shows me random low amplitude noise
> >     

> > -   A3 TP2 I see 5.38VDC
> >     

> > 

> > My serial number is 2432A01344 and I have the 10811-60109 OCXO (and no
> > 

> > options fitted, so the chassis is clean of battery corrosion).
> > 

> > Thanks all for the help!
> > 

> > Jared_______________________________________________
> > 

> > time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send
> > 

> > an email to time-nuts-leave at lists.febo.com
> > 

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> 

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