Test Equipment Anonymous

The interconnects are like the old 50-way SCSI IDCs, but the cable has 22 conductors with spaces in between and to match that spacing the pins/sockets are in a single row with 0.1" pitch instead of two rows. Unlike the two-row connectors there isn't a latching cover to keep pressure on the top ...

AVGresponding wrote: ↑Fri Jan 30, 2026 2:22 pm You'll find out which one it is when you use it to repair something...

Indeed, that's why they were straight into the scrap bin. I bought a big box of many, many thousands of Philips 1N4148, so I don't mind throwing out any that might be suspect.

To be fair, interconnects and edge connectors are a likely trouble spot with any 30 plus year old kit. There are tarnishing problems and cables become stiff with time. I've had a couple of problems fixed by removing boards and re-seating them. Connectors will have a specified number of insertions, ...

I've just made a mental note not to buy an HP3314A function generator if I spot one. This applies to the 3325B, too, in terms of interconnects. I've put my 3325B into storage because the interconnects were driving me round the twist. I don't have the same problem with the 3325A, which uses slightly...

I dropped the dodgy 1N4148s into my "scrap" bin but I could retrieve them. I'd be very interested to try measuring if it's just one or two. I can improvise a computer-controlled curve tracer and out the DUT in a temperature cabinet. Curve tracing is usually quite good for spotting intermi...

Looks like the A1 and A2 interconnects are the problem, not just the conductors but also the connector continuity. I've managed to get sync to come back but only when I'm pushing the connector to maintain the connection. The main output isn't working, though. I am so tempted to just hard wire it all.

The computer has a time constant assisted inverter to run its reset line, that's connected to a comparator that checks various things about the 5.1V supply. The 5.1V supply watches the 15V supply to check it's >13V, the 15V supply was dropping to 11V because of the 1N4148. And now I've found that pr...

Would UM6264-12 be of any use? Personally if the diodes are faulty, I wouldn't preemptively replace the RAMs I've got a 6264-12 in there at the moment, it's in a socket, soldered to some stripboard, with wires soldered between the stripboard and the top side of two more µPD444C sized sockets, which...

Also, I'm clearly too tired to be typing stuff into the internet, I used a 6264, not a 62256. Still 16 times more capacity than each of the original chips. I *think* the 6264s came from a pile of Tandata Prestel terminals that I bought, must've been around 1990, from a very strange junk shop that wa...

I dropped the dodgy 1N4148s into my "scrap" bin but I could retrieve them. I decided it'd be quite a lot of work to build a test jig to get them to the right temperature to replicate the conditions inside the 3314A. I might fish them out if I decide that would actually be fun. My component...

I've switched it off for the night, there were no restarts since the diode replacements. That's the longest it has run non-stop since I've owned it. Maybe a good sign, maybe not. I'll repeat the test tomorrow. If I've fixed that problem I will try to source a couple of replacement 1k x 4bit µPD444 s...

It was this page https://gideonlabs.com/posts/glass-diode-failures

I think that was a problem with a particular batch, from the way I'm reading it, so it might not be relevant, but it seems like a way that the diode can be intermittent that I'd not considered before.

I've replaced almost all the things on the list, I left the original 20kΩ reference/feedback divider resistors in place, though. Loads of new diodes, including CR125, which feeds +15V to the op-amp's power pin, in case that was intermittent. It's back on test. Edit: I have higher hopes this time bec...

It looks to be as if the slope is modulated with a 100Hz FW rectified waveform. It's not very clear. That may shed some light on the problem. Yes, I agree, it looks like the ripple on the unregulated side of the pass transistor. The ripple stops when it reaches 11.1V, which has to be about what you...

I captured a nicer picture of the ramp down from 15 to 11.08 volts. It's not quite the smooth slope that I thought previously, but it's still ramp-like.

I hope it fixes it. Bad connections and bad cables have caused me plenty of problems in the past. There have been a few false dawns so far, but fingers crossed. No, no, the false dawns will continue. Swapping the cable has fixed the occasional E51, E30, E31 and E34 but very late last night, after I...

Instead of that horror I've just reversed the cable end to end which seems to have fixed it. This shouldn't work but it did, for now at least. Let's see if it glitches…

No, but I'm not worried about the heat there, they were toasty but not danger toasty, more hot radiator that you wouldn't want to keep a hand on too long. I've decided the interconnect between A2 and A3 needs to be replaced. It's just too sensitive to position and movement to make faultfinding produ...

tggzzz wrote: ↑Tue Jan 27, 2026 12:50 pm Pull and push and twist the buggers?

They're quite hot at the moment, but wiggling them does nothing, no restarts, no DSO triggering.

I didn't resolder the rectifiers when I last had the board out, because they looked fine under magnification and at that point they didn't seem like a likely cause. It might not even be the solder end that is bad, perhaps the rectifiers themselves are mechanically knackered and achieving near magica...

I've already gone some way to exhausting the mains-borne trigger theory by producing many, many glitches by turning on some of my more unruly appliances. I managed to trigger the DSO a few times with very short duration spikes but the 3314A didn't respond to them at all. Still no glitches today and ...

It's as if you're tempting me into building a pulse swallower that works on the mains! That would be quite a neat gadget and cheaper than buying one of those huge AC power sources that can be programmed to misbehave. I don't think it can be a missing cycle, though, there's a reasonably large capacit...

Wouldn't it be nice to know whether the ch1 droop was due to a missing input cycle or an extra load on the PSU output. Key features of the ch1 droop are the voltages, the linear fall and rise tends to imply constant current, and the 10ms falltime and 7ms risetime. If you used a BJT plus resistor ac...

I don't think adding capacitance will help, there's no IC resetting as such - the reset happens because there's a power good monitor checking the +15V line and that will turn off the 5.1V supply if the voltage drops more than a volt or so. And it is dropping more than a volt or so, around 3.5V, for ...

I checked the 22MΩ, it's within tolerance. Back to waiting again now, as I'm hoping to get more detail of a glitch, not that it'll help me much.