Test Equipment Anonymous

EC8010 wrote: ↑Wed Nov 19, 2025 10:20 pm If memory serves, the 1977 design was discrete component. These days, Mr Self does everything with a 5534A. Mind you, you have to work hard to better a 5534A, especially for the price. 17 days annual leave would certainly put me off; there would need to be some stunning advantages elsewhere to compensate.

It was. Picture below; phono input board top left, main preamp right.

He used current sources in the long-tailed pairs' emitters, and temperature compensated the current by using red and green LEDs. Pretty, but he later admitted that was unnecessary overkill.

I noticed that the lenses on that Yashica were quite slow. I have a lovely 50mm f/1.4, but perhaps that's too long a lens for a stereo camera? And the required distance between the lenses doesn't help.

Slow lenses are irrelevant for stereoscopic; depth of field is critical. Ideally you prefer f16, and have to be very careful with composition below f8. The stereo Realist has, IIRC f3.5 lenses, and it is very rare to use that setting.

Zenith wrote: ↑Wed Nov 19, 2025 11:19 pm

tggzzz wrote: ↑Wed Nov 19, 2025 8:09 pm My first hifi construction was a Heathkit AR2000 with my father, over Christmas when I was 13/14.

My second and last was Doug Self's first preamp, published in Wireless World c1977. I remember discussing the reasons I chose that preamp during my first interview at HP in Scotland. It was one of the more effective and interesting interviews, and I would have joined HP then, but there holidays were a miserly 17 days/yr.

Judging from stories I heard, and from people I came across who'd worked there, I consider that a torpedo grazed your bow.

My hi-fi amp is a Linsley-Hood design published in WW in the late 80s and offered as a kit by Hart.

Any specific example of torpedo action?

I didn't pick up any bad vibes at the time, but then the baseline comparison was with GEC/Marconi companies!

Applied to 6 GEC/Macaroni companies on the milk round, offered interviews to a dozen companies, had one letter which looked like an acceptance even without an interview. At one site in Borehamwood I was talking to a security guard while waiting for the charabanc, and noted that we were all looking around and seeing lots of other places. He replied "And I'm sure there will be other places", with an unspoken "won't there".

Zenith wrote: ↑Wed Nov 19, 2025 12:05 pm

bd139 wrote: ↑Wed Nov 19, 2025 9:47 am
As for printing, I have a little Canon Selphy printer that does 6x4" prints on dye sub as good as a professional print shop. That's a reasonable option. Laser printer, hmm not sure about that

But yeah phone / digital cameras are good for documentation and utility.

How often do you want a really good print you can frame or give someone? A fairly horrible print from a laser printer can be good enough. It might be purely functional. Incidentally, the image quality on passports and other official documents is awful these days. I thought professional photo printers were wax sublimation and cost thousands. The cost doesn't matter if the printer produces 100 prints a day on average and you are charging for them.

I print them quite regularly these days. The Selphy is a very nice little dye sub printer. Costs about £120 and then the dye-sub and paper packs are £30 for 100 prints which is quite reasonable. Anything larger is much much more expensive.

Output:

Zenith wrote: ↑Wed Nov 19, 2025 12:05 pm It's crossing my mind that instead of using the Nikon L27 compact camera, which cost about £50 when it was new, and is definitely point and shoot, I might splash out and buy a top end compact with a 1" sensor. There aren't as many on the market as a few years back, but they are around s/h, and there are a few new ones aimed at vloggers. The image quality would be better and it would cope with difficult conditions more easily. I'd worry about it a lot more.

The digital cameras have come a hell of a long way in the last few years to be fair. The mid-top line ones are all "mirrorless' now which gives you really high end DSLR performance at way under half the weight. My (old) Nikon Z50 was pocketable with the 16-50 zoom lens on it. There are smaller ones from Fuji etc as well.

Zenith wrote: ↑Wed Nov 19, 2025 12:05 pm Cameras you don't take out because they are too big and heavy, aren't a great idea in my opinion, however good the picture quality. It used to be that film SLRS could cope with conditions that simple cameras just couldn't. Basic digital cameras are surprisingly capable.

This is still true. The limiting performance factor is the pixel size and the glass in front of it which are pretty much limited by physics. Which is why smart phones, even the top end ones, are rubbish. I do a lot of travel and drag a full frame mirrorless around me these days. No big deal.


I can do 4 days fine with a single under seat bag on a plane somewhere with that in it.

Zenith wrote: ↑Wed Nov 19, 2025 11:38 pm

EC8010 wrote: ↑Wed Nov 19, 2025 10:20 pm I noticed that the lenses on that Yashica were quite slow. I have a lovely 50mm f/1.4, but perhaps that's too long a lens for a stereo camera? And the required distance between the lenses doesn't help.

I have a 50mm f/1.4 on a Minolta. It's noticeably bigger altogether than an f/1.8 and positively dwarfs an f/2.8. f/1.4 was definitely a step up in price. f/1.2 were even bigger and more expensive. I think they were usually 55mm. There was a ludicrously expensive and over-the-top Canon f/1.2 aspheric. There's also weight to consider on what's bound to be a fairly heavy camera to begin with. Later on there was something of a move towards 35mm lenses as standard on SLRs. Without knowing much about it, I'd guess wide field is much more useful in stereo photography than narrow field.

Width of field isn't too important; you can usually move your backside.

Depth of field is vital, and a wide angle lens helps in that respect.

Key features of the Stereo Realist are

• standard 35mm stock
• field of view suitable for snapshots
• lenses at eye spacing
• square frames, not vertical half frames
• frames interleaved on the film

The last two meant that I always wrapped the (metal) film canister in masking tape marked "do not cut, return as roll, non-standard spacing", and repeated that on the (plastic) canister containing the film canister. Never had a problem.

A striking feature about the lenses on that Yashica was the linkages between them. They looked a bit Heath-Robinson, but I can't imagine a better and easier way to link them.

Hence my original description of "cut and shut"

I looked up the circuit of the Advanced Preamplifier (WW November 1976). I'd like to thump Douglas Self for drawing some circuits with the positive rail at the bottom and negative at the top, yet others with correct orientation! Fortunately, that appears to have been a one-off. Agreed, it was advanced for its time; split RIAA equalisation was unheard of, despite its obvious advantages.

Yesterday, I finished another lathe accessory. The trouble with screw cutting on the lathe is that you run the lathe at its lowest speed in order to see what's going on and avoid accidents. Unfortunately, that means you have enormous torque, so that when something goes wrong, it goes seriously wrong. So a cranking handle fitted to the far end of the spindle allows you to rotate the work gently, sense when something isn't quite right and correct it before breakage. So I made one. The large lump has a radial M6 grub screw with its end turned down to 4.05mm to engage with the slot in the lathe spindle. The bar is 1/2" square section, secured by an M8 screw. The rotating handle is lignum vitae from a 1958 lawn bowl bearing on an M8 stainless steel bolt.

EC8010 wrote: ↑Thu Nov 20, 2025 12:26 pm I looked up the circuit of the Advanced Preamplifier (WW November 1976). I'd like to thump Douglas Self for drawing some circuits with the positive rail at the bottom and negative at the top, yet others with correct orientation! Fortunately, that appears to have been a one-off. Agreed, it was advanced for its time; split RIAA equalisation was unheard of, despite its obvious advantages.

Urgh, yes

The LTP layout follows the schematic "design pattern" for NPN transistors - but for some reason he uses PNP transistors.

The rotating handle is lignum vitae from a 1958 lawn bowl bearing on an M8 stainless steel bolt.

Would the bowls fraternity regard that in the same way as we regard people who buy TE for valves and nixies?

PNP BJTs are very slightly quieter than NPN. It's generally <1dB, mind.

Oooh er! Hadn't considered that. Anybody buying aged test equipment for its valves is an idiot; if not worn out, the valves will be well on their way. Would I buy a DMM using nixies? Not really; I want better accuracy than was achievable in that era. I can't imagine much useful test gear is lost to that cause. I know the late Jim Williams favoured a valve oscilloscope but I can't imagine any valve test gear would be useful today. I await a frenzied response telling me how wrong I am.

tggzzz wrote: ↑Thu Nov 20, 2025 12:57 pm

EC8010 wrote: ↑Thu Nov 20, 2025 12:26 pm
The rotating handle is lignum vitae from a 1958 lawn bowl bearing on an M8 stainless steel bolt.

Would the bowls fraternity regard that in the same way as we regard people who buy TE for valves and nixies?

Lignum vitae bowls were made in pairs or quads of different sizes, and with different biases set. Some have cracks or have otherwise not stood the test of time well. They are not things anyone interested in bowls would use. Looking on ebay, tatty old bowls can be bought for £10-15 each, sometimes less, and with the suggestion they could be used for wood turning. There are also various things made from old bowls. These days if you are interested in playing bowls, you probably buy modern ones made from synthetic materials.

The objection I have to people stripping valves from old TE, is that they are wrecking or making harder to restore, interesting items, to do something silly. I don't have much time for valve hi-fi or Nixie clocks.

Zenith wrote: ↑Thu Nov 20, 2025 2:05 pm Lignum vitae bowls were made in pairs or quads of different sizes, and with different biases set. Some have cracks or have otherwise not stood the test of time well.

I have found cracks when cutting them up; really annoying when you are close to final size and discover a crack. The quad set I've just started cutting up cost £40.

EC8010 wrote: ↑Thu Nov 20, 2025 2:00 pm Oooh er! Hadn't considered that. Anybody buying aged test equipment for its valves is an idiot; if not worn out, the valves will be well on their way. Would I buy a DMM using nixies? Not really; I want better accuracy than was achievable in that era. I can't imagine much useful test gear is lost to that cause. I know the late Jim Williams favoured a valve oscilloscope but I can't imagine any valve test gear would be useful today. I await a frenzied response telling me how wrong I am.

I wouldn't argue against your position strongly, although I do have two or three pieces of TE using valves or Nixies. I don't use them much and I certainly don't seek out TE like that these days. Valves can throw up unexpected results when you put them on a tester. A grotty looking octal with the envelope taped to the base very often performs at the top end of its spec.

However, there are one or two members here who are into Tek 500 series, vintage HP sig gens and such, and they've sometimes bought things which have been ravaged by valve strippers. They might see the world differently to you.

EC8010 wrote: ↑Thu Nov 20, 2025 2:00 pm Oooh er! Hadn't considered that. Anybody buying aged test equipment for its valves is an idiot; if not worn out, the valves will be well on their way.

Plenty of audiophools around. I inherited a couple of such artefacts, and took pleasure extracting excessive money from such people.

Would I buy a DMM using nixies? Not really; I want better accuracy than was achievable in that era. I can't imagine much useful test gear is lost to that cause. I know the late Jim Williams favoured a valve oscilloscope but I can't imagine any valve test gear would be useful today. I await a frenzied response telling me how wrong I am.

Yes: if you want accuracy and reliability.

No: if you like the old artefacts for their own sake, and seeing how people stretched technology almost to breaking points. Examples...

Counters (and even computers/calculators) based on dekatrons: they are just fun to watch.

Panaplex displays are very restful to look at. Ditto the early HP "dotted 7 segment LED" displays in some of their small counters.

Strangely wonderful mechanical constructions to extract as much performance as possible such as the 500MHz marker output in a Tek 184. Spotting the two valves and L69 and L70 is a useful pedagogical technique for those who believe you can buy resistors, capacitors and inductors


Also for how to do a divide-by-N counter with only a two transistors plus (IIRC) four resistors, a couple of diodes and a couple of capacitors.

I'd like to get my hands on some weirder displays, e.g. those 60s displays which project incandescent bulbs through masks onto a large screen. Not prepared to pay much, though.

However, I'll avoid the moving coil meter used to show a single digit in a digital counter; too pernickety and ugly.

EC8010 wrote: ↑Thu Nov 20, 2025 2:00 pm

Oooh er! Hadn't considered that. Anybody buying aged test equipment for its valves is an idiot; if not worn out, the valves will be well on their way. Would I buy a DMM using nixies? Not really; I want better accuracy than was achievable in that era. I can't imagine much useful test gear is lost to that cause. I know the late Jim Williams favoured a valve oscilloscope but I can't imagine any valve test gear would be useful today. I await a frenzied response telling me how wrong I am.

Well gee, I certainly have been called worse in my time but if "idiot" is referenced to the subject at hand then I guess I'll wear that badge proudly. I regularly seek out vacuum tube TE because I grew up with VT's and I enjoy working on them. Or should I say "valves" so there's no misunderstanding. Whether VT TE has a place in today's scheme of things is not for you to decide but if you don't want anything to do with them that's certainly your call and I won't call you an idiot.

Zenith wrote: ↑Thu Nov 20, 2025 2:18 pm

EC8010 wrote: ↑Thu Nov 20, 2025 2:00 pm Oooh er! Hadn't considered that. Anybody buying aged test equipment for its valves is an idiot; if not worn out, the valves will be well on their way. Would I buy a DMM using nixies? Not really; I want better accuracy than was achievable in that era. I can't imagine much useful test gear is lost to that cause. I know the late Jim Williams favoured a valve oscilloscope but I can't imagine any valve test gear would be useful today. I await a frenzied response telling me how wrong I am.

I wouldn't argue against your position strongly, although I do have two or three pieces of TE using valves or Nixies. I don't use them much and I certainly don't seek out TE like that these days. Valves can throw up unexpected results when you put them on a tester. A grotty looking octal with the envelope taped to the base very often performs at the top end of its spec.

However, there are one or two members here who are into Tek 500 series, vintage HP sig gens and such, and they've sometimes bought things which have been ravaged by valve strippers. They might see the world differently to you.

Getting back into playing with vacuum tubes for audio amplifiers is what initially led me down this test equipment collecting rabbit warren. Being on some of the DIY forums led me to purchase an HP 3562A Dynamic Signal Analyzer. This led me to the HP mailing list, where members at the time happened to be bitching about nixie tube rapists buying and stripping counters for their displays and scrapping the rest. I then perhaps foolishly bought a 5245L from the 'bay to 'save' it from the vultures, and this reignited interest in nixies (had played a bit with them back in HS in the early 80s). I started seeking out OTHER HP stuff with nixies, then expanding my interests to TE in general and now have a house on the verge of collapse.

As for usage, the HP 3439A and 3440A DMMs are permanent fixtures on my bench and get frequent use and the others come out to play occasionally as well. The other workhorse DMM is a Data Precision 3500 with a Panaplex display. If extreme precision is needed the 3455A or 3456A come out, but for day to day use the others by and large suffice.

The counters are largely for their cool factor as I don't typically have a huge need for frequency counting (though I am really afraid to actually count how many are lurking about here...), and my 5340A with nixie display has option H1, extending its top end from 18 to 23 GHz, so it's quite capable.

For my tube audio stuff, I normally use 'regular' tubes, and don't pretend to be an audiophool who can hear the differences between gray or black plate 12AX7s, or that 6DJ8s expand the sound stage and make the highs higher, the lows lower and cure cancer so no 'tube rolling' goes on here. 6DJ8s belong in Tek scopes and other test gear, and it infuriates me when people try to sell stripped carcasses.

-Pat

MED6753 wrote: ↑Thu Nov 20, 2025 4:43 pm Well gee, I certainly have been called worse in my time but if "idiot" is referenced to the subject at hand then I guess I'll wear that badge proudly. I regularly seek out vacuum tube TE because I grew up with VT's and I enjoy working on them.

But I don't think you can have the "idiot" hat if you're actually going to use the valved test gear. What I meant was that to buy the test gear purely to strip the valves out of it is an extremely expensive way of buying used valves. Admittedly, those old Tek oscilloscopes with distributed amplifiers have rather a lot of valves, but the days of buying a Tek 545 with power supply on lab trolley for £20 are long gone. (I bought one for work many years ago because we needed the trolley.) The Panaplex display on my Solartron 7075 DMM is lovely to behold, but the meter behind it is nothing like as good as my (much newer) Hioki DM7275.

That 500MHz PCB is wonderful,with C64 the trimmer capacitor between L70 the centre-tapped inductor. And as for L69's coupling critically adjusted by bending it towards L70... Magic! Are those nuvistors? I'd have loved to shown something like that to the students when I was teaching. Looking at audio prices, there seem to be a lot of people around with more money than sense. Over the last twenty years, I've dithered and havered for six months over a piece of audio gear yet spent the same amount of money (and more) on test gear with nary a qualm.

EC8010 wrote: ↑Thu Nov 20, 2025 7:52 pm Admittedly, those old Tek oscilloscopes with distributed amplifiers have rather a lot of valves, but the days of buying a Tek 545 with power supply on lab trolley for £20 are long gone.

Zenith and I went to the Telford hamfest, where they couldn't give Tek7000 series plus plugins away. Back in the day I never liked them anyway; I preferred 465s

(I bought one for work many years ago because we needed the trolley.) The Panaplex display on my Solartron 7075 DMM is lovely to behold, but the meter behind it is nothing like as good as my (much newer) Hioki DM7275.

Yeah, but you can tweak adjust 7075s, to you heart's content. No comments on the wisdom of that, please!

That 500MHz PCB is wonderful,with C64 the trimmer capacitor between L70 the centre-tapped inductor. And as for L69's coupling critically adjusted by bending it towards L70... Magic! Are those nuvistors? I'd have loved to shown something like that to the students when I was teaching. Looking at audio prices, there seem to be a lot of people around with more money than sense. Over the last twenty years, I've dithered and havered for six months over a piece of audio gear yet spent the same amount of money (and more) on test gear with nary a qualm.

You are actually looking at C70; C64 is hidden on the other side of the double-sided PCB. L70 is the horseshoe "half transformer" between the two nuvistor anodes. (Nuvistors are still available NIB on fleabay for ~£7, IIRC) L69 is indeed the piece of bendable wire; move it closer to L70 if the output isn't strong enough

I wonder how much that gold is worth, another form of TE rape.

Zooming out on the schematic shows other interesting features...
The "ablist" joke...
Measuring times in units of conductance (a pet peeve of mine)...
The nuvistor at the bottom left is a tuned circuit frequency doubler, 50MHz on the gate, 100MHz on the anode...
The 200MHz and 500MHz filters.

For fun, I've also shown one of the two transistor divide-by-5 circuits. 1ms pulses on D260, 5ms pulses on Q275 emitter. Q273 merely buffers the output to drive external circuits. If you monitored the voltage on C263 with an analogue voltmeter, and you would have a digital display of the current count.

tggzzz wrote: ↑Thu Nov 20, 2025 8:34 pm

EC8010 wrote: ↑Thu Nov 20, 2025 7:52 pm Admittedly, those old Tek oscilloscopes with distributed amplifiers have rather a lot of valves, but the days of buying a Tek 545 with power supply on lab trolley for £20 are long gone.

Zenith and I went to the Telford hamfest, where they couldn't give Tek7000 series plus plugins away. Back in the day I never liked them anyway; I preferred 465s

TBH looking back, and had I been better prepared with a list of Tek plugins worth acquiring, that may well have been a serious missed opportunity. It could well have yielded a few 10mA tunnel diodes as used in Tek 475s, for which I have a thing.

Missed opportunities aside, I did pick up a very respectable (non-working of course) 475, with a front cover and document pouch full of very respectable probes for a fiver. A couple may have been the original 250MHz probes it came with, complete with witch's hats. The other seven weren't rubbish. The seller also chucked in a genuine 465B manual.

Perhaps unwisely, I sported another fiver with the same seller, and found myself in possession of a Hameg 20MHz storage scope plus manual. It seems to work as well as it ever did. It has a missing knob and broken off shaft.

tggzzz wrote: ↑Thu Nov 20, 2025 8:34 pm Measuring times in units of conductance (a pet peeve of mine)...

Ah yes, s (seconds) and S (Siemens). I had to stop and think about that one; being a bit old-fashioned, I prefer mA/V. The one that drives me really dotty is people writing 270K. K is for temperature, k is for kilo. I even have an NPL coffee mug with K on it. But as for destroying test gear for its gold... That's just heresy.

I'm with Cubdriver on the "long plate vs black plate" nonsense. Valves are pieces of production engineering and have significant tolerances; so it's rare to find statistically significant differences between constructions. But I do like my audio electronics to glow in the dark. Turn the lights down, select suitable music, 85% cocoa dark chocolate, add a crystal tumbler of single malt, and what more could you want?

EC8010 wrote: ↑Thu Nov 20, 2025 10:55 pm But I do like my audio electronics to glow in the dark. Turn the lights down, select suitable music, 85% cocoa dark chocolate, add a crystal tumbler of single malt, and what more could you want?

A big J with Durban Poison, or better Malawi Cob.