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

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1980s_john:

--- Quote from: 1980s_john on September 30, 2016, 09:37:07 pm ---
--- 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.
--- End quote ---

I finally took the front panel off today to fix the buttons. I found it impossible to remove the keycaps from the switches, I tried pulling them straight up but didn't want to pull too hard and break the switch. I fixed the metal strip back into the Gate Mode switch and it worked fine. I checked the other switches and found three where the metal strip had come out at one end and was held by the neighbouring switch. I fixed two of them but on the third the strip snapped in two whilst I was trying to refit it (not easy!). I took the pieces out and reassembled the unit, luckily the switch works fine without the spring - it is the Range Hold switch and pressing it toggles the setting nicely.

All done now, thanks for the  helpful tips and offers of parts,
Regards,
John

Mrt12:

--- Quote from: 1980s_john on March 27, 2015, 11:53:41 pm ---
--- Quote from: orin on March 04, 2015, 06:03:16 pm ---If you have the DC fan, it's likely that the contacts on the relay socket have opened up.  See the service note in my post above.  The relay socket is a 27E213, Digikey part number PB806-ND.  If it is the relay socket and you do the modification in the service note, you probably don't need a new relay; I'm still using my original relay.  Anyone with a 5335A should make sure that this modification is done and switch to a DC fan.  The 5V supply relay socket contacts get hot, fatigue and eventually, when they cool down, don't make contact with the relay any more.
--- End quote ---

Thanks, my relay seems to be OK. However removing it shows a black heat mark on the socket, presumably where the 5V passes through. Thanks for the service note, I must give it a go.

The HP part for the relay is 0490-1172. Printed on the side is the code R10A-E1-X6-V430, and a date code 7923. ebay shows loads of R10-E1-X6-V430, is the R10 2A relay and the R10A 5A then?

Regards,
John

--- End quote ---

Hi guys,
I have the exact same problem! it is very weird - the input voltage to the voltage regulators seems OK, butno output. Somebody mentioned that the relay socket is actually the problem when this symptom occurs. Can someone explain this in more detail?
With the missing -15V, I got Fail 5.1 on my counter, which means 'Interpolator failure', but I don't really believe that the interpolators are damaged - I think they simply don't work if some of the supply rails are missing....

(just in case an interpolator is blown: is there a spare?)

1980s_john:
Hi Mrt12, please read all the replies on this thread. Regarding the fan change and relay socket, see the service note (https://www.eevblog.com/forum/testgear/hp-5335a-timer-counter-anything-i-should-know/?action=dlattach;attach=128567). I found it useful to print off the circuit diagram for the relay / fan circuit, mark off the changes on paper first then do for real. I can find my paper copy and scan it if wanted. The circuit change is quite simple and results in the high current PSU output feeding through 2 relay switches in parallel thus reducing the current through the socket contacts. As the old relay socket is likely to be heat damaged a new one with good contacts is recommended.

The PSU output voltages need to be correct before worrying about anything else, I had some shorted tantalum capacitors and a failed -15V regulator (7915). I have a spare relay socket available for price of postage.

Regards,
John

lowimpedance:
Found two service notes (23 and 24) for the 5335a counter at work and this thread seems to be the most appropriate place to archive them.

rob.manderson:

--- Quote from: lowimpedance on November 21, 2018, 11:31:01 pm ---Found two service notes (23 and 24) for the 5335a counter at work and this thread seems to be the most appropriate place to archive them.

--- End quote ---

Ah ha! Service note 23.  I found this exact effect on mine.  Since I have no need for rear panel inputs I simply removed them.

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