Test Equipment Anonymous

That HP is very tidy and elegant. One of the rare opportunities to feel annoyed with British mains sockets, as you'd be lucky to fit just one on that front panel and even then you'd have to move the knob off-centre and use all sorts of bevel gears to get the driveshaft back to the middle of the vari...

I've a memory of most of the Jackson Bros stock being destroyed in the fire at Electrovalue after the move from a shop in Englefield Green to larger premises in Egham. After that Mainline bought what was left of Jackson Bros, tooling and some stock that had escaped destruction or something. I've for...

I was digging through the components in tubes to find these and then I realised I was mixing up two different repairs that I did at the same time. The level shifter CMOS is actually in my RACAL 1792, the CMOS that failed in the 2019 is a CD4056BE which isn't an endangered species just yet.

The "Curcuit" for this RF signal generator is suspect, the JFET Q1 doesn't appear to have anything but a capacitor connected to its drain.

Just done a three-way test-off with the modern T7-H tester, a Wayne Kerr B424 component tester and the Marconi TF2700. First I tried a NOS 68µF 63V Philips. This showed up as 75µF on the T7-H, but with 1Ω ESR. The Marconi indicated 34.3µF and 34µF on the 1,000µF range as a confidence test. It seemed...

Here's a link to a permatemporary web page with a link to my extracted firmware. https://mossyvale.co.uk/te/

They're a decent meter. The SRAM battery is very problematic though; I'm contemplating binning off rechargeables on mine (I did do a 2x AAA mod but prolonged lack of use results in cal loss) in favour of hot-swappable lithiums of some sort. EDIT: Oh, btw, if yours has the GPIB, TheHWcave is looking...

Excellent; another aged meter brought back to life. And it looks like its display goes to 3.9999, making it quite reasonable accuracy. Useful. Yes, it's a 40,999 count design which makes it fine as a basic bench meter. Apparently there's an earlier 4503 that is 20,999, which must be a bit confusing...

Did Keithley buy any of RACAL-DANA? I know that case style, it's from Keithley's 179, 177 etc, except they were not brown (except the 175, which was, maybe others too). RACAL-DANA sold rebadged 179s as the 4002, so there were clearly some business relationship in the past. I had assumed Thales got a...

DC Current calibration is now complete, it really, really needed the screening metal to be in place.

Here's another DMM that I'd been curious about for quite some time. It has plenty of features but fairly basic performance. https://live.staticflickr.com/65535/55222264129_406f5584a6_c.jpg This had two major faults, the NiCd battery had failed and leaked and the power switch is very reluctant to swi...

Mine doesn't have the "mi" logo, so perhaps that makes it earlier. Marconi struck me as a company that wouldn't have taken to the idea of "branding" and "logotype" easily or quickly.

I imagine if I re-read the whole sub-thread carefully, I might be able to catch up on exactly what is/isn't being referred to. "For more information please reread" (The reference awaits spotting) That has to be Scarfolk although as with most Scarfolk stuff I always get the feeling that I'...

I've been threatening to pick one of these bridges for a while and the first rally of the year for me was the opportunity. I had to rebuild the outer range multiplier selector knob as the plastic had crumbled around the centre. I had most of the pieces, as they'd been held captive by the design of t...

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...