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HP 5335A Timer / Counter - Anything i should know?
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1980s_john:
Hi,
I've checked the voltage rails with a scope and didn't see any major problems (50mV of noise relative to chassis).

I think I've found a problem with the B channel trigger, please can someone with a fully working 5335A try the following simple test as a comparison.

Set all buttons out, rotate A and B trigger level knobs fully counter-clockwise (past click point), remove all cables.

Power on - check A and B LEDs. I see A LED lit and B LED unlit. Display shows 0.

Press 'Trig Level' button - shows A trigger level voltage on left and B on right.

I get:
0   -4.80

When I rotate trigger A level knob, left digit changes from 0 to -5.19, then increases through 0 to 5.20.

When I rotate trigger B level knob, right digit changes from -4.83 to -0.60.

I assume trigger B voltages should look the same as trigger A  :(

Regards,
John

woodchips:
I have just scrapped some 5328 counters, all of which had the option 10 hi-stab oscillator. No idea if they will fit anything else.
Vgkid:

--- Quote from: woodchips on October 04, 2016, 04:35:01 pm ---I have just scrapped some 5328 counters, all of which had the option 10 hi-stab oscillator. No idea if they will fit anything else.

--- End quote ---
As new as the 5328 is, it should use the 10811 series oscillator. It is used in much hp gear.
1980s_john:

--- Quote from: 1980s_john on October 04, 2016, 01:21:15 pm ---When I rotate trigger A level knob, left digit changes from 0 to -5.19, then increases through 0 to 5.20.

When I rotate trigger B level knob, right digit changes from -4.83 to -0.60.

I assume trigger B voltages should look the same as trigger A  :(
--- End quote ---

Hi,
With help from the Yahoo HP/Agilent group I found the problem was with A2 Amp Support U10, a MUX08 8-to-1 analogue mux that wasn't switching correctly. This provides the trigger level voltage into the B channel on the A3 input board. Once replaced the unit now passes self test with no errors (FE Pass), so I can now tidy it up and try and fix things like the relay socket and dodgy front panel switch.

Thanks for help & advice,
Regards,
John
PS - earlier changes were 4 tantalum caps on A3, 7915 on A1, rewiring relay to double up 5V contacts / change fan from 110V to 24V
1980s_john:

--- Quote from: orin on January 08, 2015, 08:34:30 pm ---I strongly recommend replacing the relay socket and implementing the wiring change in the service note or one day, you'll turn it on, the fan will run, but you will get no display.  The relay socket is part #27E213, PB806-ND from Digi-Key. 

--- End quote ---

Hi,
I ordered a 27E213 socket and it worked well as a replacement. However when I removed the old one from my 5335A the original socket was a 27E129. The only difference in specs is that the 27E129 has a grounding strip and the 27E213 doesn't, but for this application either is fine.

Regards,
John
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