Hi,
I plugged my 5335A back-to-back with a lower spec HP counter in our lab, and the counter and timebase out parts both worked fine. I need to tweak the crystal trimmer one day against a GPS based oscillator, the specs for the HP OCXO are way beyond anything else in out lab.
I tried the diagnosis self test and it gave FAIL 7.3, so some issues to sort out, so I am looking for some advice please.
I have a copy of the service and operations manual (scanned by KN5U - thanks!), but I am rather stuck. As I wrote earlier:
I checked voltages for +15V, -15V, +10V, +5V and -5.2V and all were good. (Somehow I forgot to check 3V.)
Referring to table 8-7 on page 8-59 voltages as per my not good DVM are all within spec:
+15V = + 15.70V
-15V = -15.10V
+10V = +10.02V (fairly sure it is within spec +/- 0.01V - need a better meter!)
+5V = +5.07V
+3V = +3.01V
+24.5V = +25.9V
However, elsewhere in this copy of the service manual someone has crossed out 15.7V and hand written 15.0V as the required voltage, and note to refer to a service bulletin. What gives please? Is this only for 5335A with certain serial numbers?
I tried to follow the service manual on from section 8-241 Troubleshooting (failure analysis), not sure what to make of the results or what tests to run next.
The one that failed was 8-293 Diagnostic #14: Front End Test. With a cable from TBO to Input A, running the diagnostic gives FAIL 7.3. The manual says 'd. Presence of signal in Channel B (FAIL 7.3 if no trigger through COM A).' So I assume the problem is in the trigger circuitry. I guess without a working trigger the 5335A is limited to working as a basic frequency counter.
I'm not sure whether the following results are a pass or fail. These are section 8-310 Diagnostic #26, #27 and #28, trigger level DVM reference test.
#26 gives a result that varies every second between -4 999 68 to -5 000 17, manual says should be -5.0000V. Is it normal to vary by +/-1mV?
#27 cycles between roughly -200 E-6 to 200 E-6, ie +/- 200uV. Manual just says GND REF.
#28 cycles between 4 999 70 and 5 001 00, manual says +5.0000V.
I do not understand section 8-312 Diagnostic #9 and #30, trigger levels A and B test. When run I see numbers between -800 E-6 to 300 E-6. Manual says 'the actual trigger level voltage for both Channels A and B can be varied over the entire range during this exercise' - I have no idea how to do this.
From the troubleshooting flowchart on page 8-57 FAIL 7.3 means a fault in the A3 amplifier assembly. Doesn't look like an easy circuit to work on so I am a bit wary of making things worse.
I am trying to fix this 5335A before returning it to a colleague, but mainly I am just trying to learn new stuff.
I hope someone here can give me some advice or pointers on which section of the manual to go to next.
Regards,
John