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HP 5335A Timer / Counter - Anything i should know?

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1980s_john:

--- Quote from: edpalmer42 on September 29, 2016, 01:42:13 am ---That piece of metal looks like it could be from one of the buttons.  .. See if one (or more) of them has no spring return.
--- End quote ---

Thanks, yes the Gate Mode Normal/Fast has no spring return. Many buttons are clicky too.

Regards,
John

1980s_john:
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:


--- Quote from: 1980s_john on September 28, 2016, 11:21:28 pm ---I checked voltages for +15V, -15V, +10V, +5V and -5.2V and all were good. (Somehow I forgot to check 3V.)
--- End quote ---

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

orin:
I seem to remember getting 7.3 errors on my 5335A when it was acting goofy due to a bad relay socket.

I'd pull the relay and take a careful look at the contacts in the socket.  More than the 5V contacts may have fatigued and spread due to heat cycling.  Then I'd put a scope on the power rails and make sure they are clean.  Only when sure of the power supplies after the relay would I try to chase down an error.

Vgkid:
Those relay sockets cause lots of grief, and different errors.

1980s_john:

--- Quote from: orin on September 30, 2016, 11:39:32 pm ---I seem to remember getting 7.3 errors on my 5335A when it was acting goofy due to a bad relay socket.
I'd pull the relay and take a careful look at the contacts in the socket.  ... Only when sure of the power supplies after the relay would I try to chase down an error.
--- End quote ---

Thanks, I'll recheck the relay socket and scope the power rails. I see Mouser UK has sockets in stock.

Regards,
John

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