Hewlett-Packard 5335A

[synx508]

It's necessary for all TE forums to have a thread on 5335As, so here goes…

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Despite already owning two completely working 5335As and a third parts unit I decided I needed another, as the well known eBay test equipment scrap dealer had been reducing the price every few weeks for what felt like months. My offer of £60 was accepted and it duly arrived without shipping damage, quite surprising given the packing which would not have stood up to ParcelForce's treatment but seemed fine with DPD.

It needed a good clean and destickering (it was, claim the stickers, part of PROJECT THOR which could've been related to EWish stuff on the Tornado unless I've got my wires crossed)

It was listed as "missing parts" but the only part missing was the DC fan and my parts unit had a good one of those. Option 010 is present but the thermal fuse was open, however the oscillator seems to work fine, including the oven controller. I've ordered some thermal fuses that should fit nicely between the original and revised HP spec. It's running with a wire link until that arrives but I'm not going to leave it unattended, just in case.
It also has option 040 which seems fine, the HP-IB is operational.

Several of the metal keyswitch springs had rusted through, I've replaced all but one of these, but I've run out of spares so the RESET switch is a bit suboptimal - has anyone here tried cutting up spring steel sheets to make these? I've seen claims of success in other places though I'm not sure my scissors skills are good enough.

This unit has a 1989 serial number but most of the ICs seem to be 1990 which is puzzling or perhaps HP repaired it, it's the single 27128 EPROM version which is a first for me, my spares unit is from 1986 and the other two are from 1984 but all have 1.1 firmware (thank goodness 1.0 looks really, really shocking), but they all use the earlier and more sketchy ROMs.

The only slight issue I have found so far is very slight crosstalk when I slam 10MHz in without terminating it, the channel B LED flashes. I will see if I can improve this when I put the thermal fuse in the OCXO next week.

[mansaxel]

I thought I had my counter fill, what with 5221A, 5245L and 5316B, adding to that also the TTi TF830 -- but no. The 5335A will again be put on the "desirable items" list for the boat anchor category, together with "any good -hp- RF signal generator good to 1Ghz" and 3325B and the 8904A..

Thanks! (I guess)

[synx508]

5335As were peak usefulness in HPs counter range. Nothing they did afterwards has the same flexibility. It's a shame they're so large, the box is mostly empty, too.

If you want nearly the same stuff in a small box with fewer digits and a life of weird faultfinding then get a RACAL-DANA 1992

3325B

At the risk of wandering way off topic, I would suggest a 3325A unless you really, really need the extended HP-IB command set and the not-very-good modulation generator that the 3325B offers. I have both and the 3325A is so much more reliable, has less digital computer noise on its output and has proper clicky buttons instead of feeling like a giant ZX Spectrum. I have lost count of how many times my 3325B tells me "FAIL 023" or "FAIL 026" or "FAIL 024" when it really means "these ribbon cables are a terrible design and need to be given a wiggle again" or "ha ha, more tantalum capacitors have exploded and taken out some resistors too". My 3325A is very rough looking but it always does what I ask of it without the drama the 3325B brings.

I recommend the high voltage output option, while it can't provide those voltages into 50Ω it is extremely useful to have them available. My 3325A has a high stability oscillator using a modern OCXO soldered onto the original slightly broken Ovenaire oscillator's option board, again, useful to have this if you don't have a gpsdo or similar, as the many digits of precision on offer are wasted with the default oscillator.

Good -hp- RF generators limits you to 8662A, I think. Newer or "better" and they're plagued with computer nonsense. I have Marconi 2019 and 2019A generators, not quite up to 8662A standards but good enough for me and reasonably repair-friendly.

[mnementh]

…Several of the metal keyswitch springs had rusted through, I've replaced all but one of these, but I've run out of spares so the RESET switch is a bit suboptimal - has anyone here tried cutting up spring steel sheets to make these? I've seen claims of success in other places though I'm not sure my scissors skills are good enough.
[SNIP]

For small things bits of spring metal, I’ve had good success using a Dremel with cutoff wheels and leftover stainless bits from disc brake kits. Both the “hardware kit” (sheet metal springs used between the pads and slots they rest in) and the pad backing shims can yield metal suitable for making small springs. Be sure to measure with digital calipers to make sure the new metal is similar thickness to original; it is easy to crack out plastic bits with metal that’s a hair too thick.

Good luck!

mnem
*tinker-ily*

[25 CPS]

I thought I'd throw out a picture of my 5335A in action. Of the counters I have, it's my favourite.