Products > Test Equipment
HP 5335A Timer / Counter - Anything i should know?
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David Aurora:
Just swapped U2 and U5, unit now counts as it should on channel A (and obviously now not on channel B). So that's some progress I guess, I don't have to press a bunch of buttons at power up to make it work.

Still no action on rise/fall and slew modes though. I can't be stuffed digging in any more today to figure out why. Given that those modes enable COM A mode though, I'm guessing there's some kind of internal routing that uses both channels for these modes and with one dead channel it doesn't work?
Dr. Frank:

--- Quote from: David Aurora on May 24, 2023, 08:59:07 am ---Just swapped U2 and U5, unit now counts as it should on channel A (and obviously now not on channel B). So that's some progress I guess, I don't have to press a bunch of buttons at power up to make it work.

Still no action on rise/fall and slew modes though. I can't be stuffed digging in any more today to figure out why. Given that those modes enable COM A mode though, I'm guessing there's some kind of internal routing that uses both channels for these modes and with one dead channel it doesn't work?

--- End quote ---

Correct, those modes require both working channels, because you need two distinct trigger levels between you measure the Time Interval.
David Aurora:

--- Quote from: Dr. Frank on May 24, 2023, 09:43:04 am ---
--- Quote from: David Aurora on May 24, 2023, 08:59:07 am ---Just swapped U2 and U5, unit now counts as it should on channel A (and obviously now not on channel B). So that's some progress I guess, I don't have to press a bunch of buttons at power up to make it work.

Still no action on rise/fall and slew modes though. I can't be stuffed digging in any more today to figure out why. Given that those modes enable COM A mode though, I'm guessing there's some kind of internal routing that uses both channels for these modes and with one dead channel it doesn't work?

--- End quote ---

Correct, those modes require both working channels, because you need two distinct trigger levels between you measure the Time Interval.

--- End quote ---

Thanks for confirming! Back to the naughty shelf it goes until I find another IC
Dr. Frank:

--- Quote from: David Aurora on May 24, 2023, 09:52:59 am ---
--- Quote from: Dr. Frank on May 24, 2023, 09:43:04 am ---
--- Quote from: David Aurora on May 24, 2023, 08:59:07 am ---Just swapped U2 and U5, unit now counts as it should on channel A (and obviously now not on channel B). So that's some progress I guess, I don't have to press a bunch of buttons at power up to make it work.

Still no action on rise/fall and slew modes though. I can't be stuffed digging in any more today to figure out why. Given that those modes enable COM A mode though, I'm guessing there's some kind of internal routing that uses both channels for these modes and with one dead channel it doesn't work?

--- End quote ---

Correct, those modes require both working channels, because you need two distinct trigger levels between you measure the Time Interval.

--- End quote ---

Thanks for confirming! Back to the naughty shelf it goes until I find another IC

--- End quote ---

Better search for a front end replacement, as this IC might be unobtainium.
This double channel electronics was identical to another HP 500MHz counter, I just don't remember the model No. This other, elder counter was quite cheap to acquire.
David Aurora:

--- Quote from: Dr. Frank on May 24, 2023, 11:16:57 am ---
--- Quote from: David Aurora on May 24, 2023, 09:52:59 am ---
--- Quote from: Dr. Frank on May 24, 2023, 09:43:04 am ---
--- Quote from: David Aurora on May 24, 2023, 08:59:07 am ---Just swapped U2 and U5, unit now counts as it should on channel A (and obviously now not on channel B). So that's some progress I guess, I don't have to press a bunch of buttons at power up to make it work.

Still no action on rise/fall and slew modes though. I can't be stuffed digging in any more today to figure out why. Given that those modes enable COM A mode though, I'm guessing there's some kind of internal routing that uses both channels for these modes and with one dead channel it doesn't work?

--- End quote ---

Correct, those modes require both working channels, because you need two distinct trigger levels between you measure the Time Interval.

--- End quote ---

Thanks for confirming! Back to the naughty shelf it goes until I find another IC

--- End quote ---

Better search for a front end replacement, as this IC might be unobtainium.
This double channel electronics was identical to another HP 500MHz counter, I just don't remember the model No. This other, elder counter was quite cheap to acquire.

--- End quote ---

Yeah, I'll keep an eye out for whatever I can get to button this thing back up I guess. IC's, whole boards, junked units, other units with the same part, whatever pops up first and gets it working again  :-//

Frustratingly I didn't even really want it but grabbed it because I'm always loaning gear to people and thought another counter couldn't hurt. But I think by the time I sort this out I'll have pumped far more effort into it than it was worth  :-DD
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