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

[Bob kb8tq]

Hi

Roughly speaking the OCXO is 40 Hz  or 8 ppm at the max end of the tune range. 
That’s a lot. 

If your OCXO is that low, then yes, it is a problem. You either need to repair or replace
the OCXO. If you are replacing, the question becomes - do you upgrade to a 10 MHz
10811? That would involve tracking down one of the assemblies that mate up with the
10811.

Bob

> On Nov 27, 2021, at 12:28 PM, Jared Cabot via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 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_______________________________________________
>>> 
> 
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>>> 
> 
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>>> 
> 
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>> 
> 
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