Audiojumble 03/03/24

[Morgan Jones]

Perhaps you can tempt me with a rocket toob or two. It's just the fan itself, not with built-in motor, that I need. A bit of folded aluminium with a central boss.

ECLL800 would need current sensing resistors in the anode circuits, a stunningly effective low-pass filter to remove the audio, then opto-isolator to get that signal down to being 0V-referred to drive an op-amp that could bias the grid voltages to balance anode currents. A lot of effort for a fundamentally flawed valve. Reading more carefully (and I wish I hadn't) there were some audio "measurements" in that Practical Wireless article. 1% THD after feedback at maximum power. And probably a horrible spectrum since the ECLL800 uses distortion cancellation between dissimilar valves. You can get less than that from a pair of EL84 before feedback. I wonder if ECLL800 was made when the German sales tax on radios etc was by valve count.

[simon]

I might be interested in a couple of C3g, a quad even. Then the C3g phono stage I've been working on for the last 18 years on and off might last as long in service...

[jack]

Take to Audiojumble or restore? ESL 63s

These were Sir Clive Sinclair's (allegedly). His cat has savaged the "gloves", he smoked like a chimney and stood coffee cups on them.

Sell or keep?

PXL_20240302_161023323_copy_1008x756.jpg (106.46 KiB) Viewed 1354 times

[Morgan Jones]

Tricky. I noticed a Radford STA15 for sale recently that was signed internally by Eric Clapton. The seller seemed to think that would increase its value. I think at Tonbridge knowledge that former owner might have been Clive Sinclair would probably reduce value. You never can tell - somebody might be looking for a pair of ESL63. I floated the idea of electrostatics with She Who Must Be Obeyed years ago. They were firmly shot down. Selling big value items is always a lottery. I took my LS3/5a years ago and there was zero interest.

[jack]

A pretty good day. Three AT types (MJ, DtB & Thomas) rocked up and SWMBO and I managed to sell a fair bit of ephemera.

[Morgan Jones]

Nice to see you there. It seems the Voltarc company went bust some time ago, and I couldn't find your natty little tester anywhere. And idea of what it produces on its aerial? AC, DC? Voltage? It wouldn't be difficult to knock up something.

[jack]

Nice to see you there. It seems the Voltarc company went bust some time ago, and I couldn't find your natty little tester anywhere. And idea of what it produces on its aerial? AC, DC? Voltage? It wouldn't be difficult to knock up something.

They are around but are now called "Masonlite ELT – Electronic Lamp Tester (Part #: 12600)" and only 250 euros!

I would put an eBay search on and wait for one to come up.

I'm happy to photograph the PCB in mine if you want...

[Morgan Jones]

Photograph would be nice. Measurement would be really nice, but if (as I suspect) it produces high voltage, but AC, it would be difficult to measure. Inside it, I would expect a ferrite transformer, with or without voltage multiplier (which should be easy to spot). Waving a scope probe a foot away ought to be able to see the RF if it's AC, enabling frequency measurement.

I bought a Post Office resistance box yesterday. One of the 10R resistors (big substantial wirewound thing) is open circuit (how?), and all four resistors along the front row are high in value. All resistors are wirewound and not non-inductive, and on unusual brass bobbins. But the worst thing is that four of the taper pins that short resistors and enable you to set resistance are bent. This is 3/16" brass and takes some bending. What do people do to things? Oh, and the wooden box isn't all that well made when you look closely. Glad I knocked the price down from £10 to £5 because it's going to be scrapped. Shame. I have a much nicer Post Office box, but it only goes down to 1R and this one went to 0.05.

Edit: And in taking it apart, I've discovered terrible soldering. One, no two, soldered joints (so far, out of only four) were axial pins through a brass shaft. There was no hint that there had ever been a soldered joint between the two parts. Make that three out of six unsoldered. No wonder I could see more recent soldering inside - somebody had already discovered this was a Friday afternoon job and tried to remedy it.

I think I've worked it out. The axial pins were made of dirty unsolderable (it's in the same periodic table column as rustalotium, corrodium, and unobtanium). I only found three pins in sixteen brass shafts that soldered. The others were all dirty and unwetted. The bent taper pins occurred when the box was thrown at the floor after a measurement had gone wrong for the nth time.

I unwound the open circuit 10R resistor. It was wound to Ayrton-Perry methodology (non-inductive) and came off as seven pieces of wire. Five ends were fully dirty, but I had clearly caused three breaks, each of which had deep nicks before my clean break. So the (1mm) wire was made of snapalotium - a new alloy on me. Those deep nicks probably explain the other resistors that are high value - they probably have deep nicks too. Looks like there won't be much worth salvaging. When I coiled the wire to throw it away neatly, it kept on breaking up, with dirty ends and tiny clean bits at the breaks. Looks like there were deep cracks all the way along. Rubbish metallurgy. All the resistors have gone in the WEEE bin. They won't be stable.

There wasn't a maker's name on this thing, so I can't point fingers. But it used specialised parts, so it wasn't home-made.

[jack]

Photograph would be nice. Measurement would be really nice, but if (as I suspect) it produces high voltage, but AC, it would be difficult to measure. Inside it, I would expect a ferrite transformer, with or without voltage multiplier (which should be easy to spot). Waving a scope probe a foot away ought to be able to see the RF if it's AC, enabling frequency measurement.

Almost certainly HV AC, probably in the 100-200kHz region - enough RF energy to excite the neon & other gasses...

If I get a chance in the next few days I will indeed measure the frequency etc.

[Morgan Jones]

That would be super. If you're right in your guess, it should destroy LW reception. Presumably, you see characteristic colours associated with different gasses?

I looked at the ends of the resistor wire fractures under a microscope and found all sorts of impurities instead of a nice metallic surface. Definitely rubbish metallurgy.

[jack]

As suspected, it's a 50% duty cycle, 1 second on, one second off RF pulse at 270kHz. Likely a couple of KV, but can't measure that at the moment - I'll have to get my trusty 40,000V probe out...!

I can't get the board out easily as they've deliberately sealed it into the box and potted some of the components in black resin.

I can see there's a TIP42C and a 555 in there, but can't see a lot else. Power is 12VDC from 8xAA batteries.

I would have though a simple royer oscillator and transformer, maybe a TV flyback? Very similar to an electric fence for chickens etc. Loads of schematics out there.

[Morgan Jones]

Don't you just hate people who hide what they've done?

[jack]

Don't you just hate people who hide what they've done?

Probably less than £10 to make including box and all components/pcb, then charge €250 for a new one!

This is probably very similar:

https://www.aliexpress.com/item/1005005975707232.html

It's available on Amazon for about £17

[Morgan Jones]

Ordered.

[Morgan Jones]

Arrived. Disappointment. Insufficient poke. Just about managed to produce an orange glow in an 85A1 neon). I am told that:

If it's blue, it's air.
If it's green, it's barium.
If it's pink-purple it's argon.

And Jack's large nixie managed a blue glow with his tester, which I assume is pokier.