Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

On Avometers, I never got the obsession with them. Maybe I'm too young. Maybe I'm poisoned by the memory of crappy analogue meters. I've used Avos before but they just don't sit well with me. Why?

1. If you drop them they are toast.
2. They have weird battery requirements.
3. They have dubious safety characteristics and always did have.
4. They're bloody huge.
5. They appear to have been universally stored in damp sheds at their current age.
6. The bottom end of the scale is really janky even on new ones (compare to HP analogue meter calibration...)

We should just let the upcyclers have the bloody things...      Seeds of discord sewn. I shall now observe from a distance     

I've owned two... they were both made of meh as far as I was concerned. This list sums up why pretty concisely... and that is why I thanked @Squarewave for collecting Avos and thinning out the herd, so I wouldn't constantly be molested by them. 

mnem
Avos are the TE equivalent of a White Elephant... something expensive to keep up but you feel somehow obligated to not just throw them in the tip. So they sit around and moulder.

[Specmaster]

@tggzzz, my post was not aimed at you in any way, it was in my view expanding and adding to your post and trying to make some form of sense as to why we are suddenly having the moderators popping up and stepping in when in the past we have always as a group been self-regulating and nobody has yet to my knowledge said sod this and has left the group, we continue to flourish and must be a quite a good revenue source for Dave.

[Specmaster]

On Avometers, I never got the obsession with them. Maybe I'm too young. Maybe I'm poisoned by the memory of crappy analogue meters. I've used Avos before but they just don't sit well with me. Why?

1. If you drop them they are toast.
2. They have weird battery requirements.
3. They have dubious safety characteristics and always did have.
4. They're bloody huge.
5. They appear to have been universally stored in damp sheds at their current age.
6. The bottom end of the scale is really janky even on new ones (compare to HP analogue meter calibration...)

We should just let the upcyclers have the bloody things...      Seeds of discord sewn. I shall now observe from a distance     

I've owned two... they were both made of meh as far as I was concerned. This list sums up why pretty concisely... and that is why I thanked @Squarewave for collecting Avos and thinning out the herd, so I wouldn't constantly be molested by them. 

mnem
Avos are the TE equivalent of a White Elephant... something expensive to keep up but you feel obligated somehow not to just throw in the tip. So they just sit around and moulder.

When compared to a decent DMM, they do exhibit many drawbacks, but as many of us love to restore the older test equipment as well as in my case audio equipment, many of these service charts/manuals actually quote what service tools are required in order to test the equipment and quite frankly a modern DMM with its input impedance being in the realms of at least 10Mohms and in some cases even into Gigohms then the voltages referenced in manuals become useless, and then you are into another rabbit hole calculating what the actual voltage should be reading with that meter rather than the required 20,000opv meter.

Therefore, IMV, if you're serious about the repair / restoration, then you do need to have at least one such meter in your collection. Allowing these meters to fall into the hands of the "Steampunk" brigade is much a cardinal sin as the hallow tube rapists of old scopes etc.

[bd139]

Ok apparently I won that first lot of transistors 

So for my money I get all NOS (yes I carefully researched all of them first) 1103 transistors, mostly high value and obscure in drawers already

55x 2N3347 - Dual PNP transistors - rare as anything - £8 a go usually
2x 2N3350 - Dual PNP transistors - also rare £8-10 a go usually
10x 2N3420 - NPN switcher - these buggers can blow off 5-8 watts in a TO39
22x 2N3439 - NPN High voltage low fT - ideal for driving CRT blanking / low speed CRT interfaces
16x 2N3634 - Fast PNP switcher that can blow off 5 watts.
199x 2N3640 - 500MHz PNP RF transistor. Fragile.
1x 2N3680 - NPN GP boring
10x 2N3702 - PNP GP boring
8x 2N3705 - NPN GP boring
37x 2N3725 - NPN pass transistor / switch / HF RF PA - nice
10x 2N3729 - NPN dual amplifier - rare as hell - £15 a go
30x 2N3823E black - JFET N VHF amplifier with low 10pA leakage - plastic package
63x 2N3823E white - JFET N VHF amplifier with low 10pA leakage - assume this is the older ceramic package
3x 2N3866 - NPN VHF/UHF amplifier / QRP PA. 800MHz.
12x 2N4209 - PNP saturated switch. Fairly quick
100x 2N4258 - NPN rubbish switch but fairly quick so might be persuaded into RF usage
5x 2N4937 - PNP low noise dual RF transistor (very very rare) 900MHz
22x 2N5014 - NPN 900V (!) switch.
23x 2N5160 - PNP 900MHz VHF RF PA.
1x 2N5055 - PNP fast driver
28x 2N5189 - NPN common low level HF RF PA transistor / SMPS driver
101x 2N5305 - NPN darlington, fast low noise.
350x 2N5401 - PNP very fast high voltage switch
52x 2N5415 - GP PNP switcher boring

Lots of goodies in there and the price wasn't too bad and I can bounce a chunk of the ones I'm not going to use to offset the price

To note I intend to fight anyone to the death on the sellers other lot of transistors 

Edit: some images:





To note that some of the dual ones are suitable for replacing the pairs in old HP and Harrison power supplies as well as designing new circuits

[Squarewave]

On Avometers, I never got the obsession with them. Maybe I'm too young. Maybe I'm poisoned by the memory of crappy analogue meters. I've used Avos before but they just don't sit well with me. Why?

1. If you drop them they are toast.
2. They have weird battery requirements.
3. They have dubious safety characteristics and always did have.
4. They're bloody huge.
5. They appear to have been universally stored in damp sheds at their current age.
6. The bottom end of the scale is really janky even on new ones (compare to HP analogue meter calibration...)

We should just let the upcyclers have the bloody things...



Seeds of discord sewn. I shall now observe from a distance     

I bet you're older than me, by quite some margin, but I love Avometers 

Yep, if you drop them, they're donald ducked, though the movements can survive, the casing will be shattered. The ones I have from the 1920s, 1930s etc are a real example of people who've taken good care of them. I think they were always intended for bench use, though I have used one before when setting up load cells in an industrial setting, where I wanted to see the swing of the movement to give me good indication from the 0-10v range of the load cell.

I guess I'm lucky to have the space for all the stuff I have. TEA, is addictive, especially Avo and Marconi stuff, it's my weakness.

Editulation: I must say the calibration of my ones are good, consistent with calibrated standards and shows the same result as a 6.5 digit Agilent DMM in cal which we have at work.

[Squarewave]

When compared to a decent DMM, they do exhibit many drawbacks, but as many of us love to restore the older test equipment as well as in my case audio equipment, many of these service charts/manuals actually quote what service tools are required in order to test the equipment and quite frankly a modern DMM with its input impedance being in the realms of at least 10Mohms and in some cases even into Gigohms then the voltages referenced in manuals become useless, and then you are into another rabbit hole calculating what the actual voltage should be reading with that meter rather than the required 20,000opv meter.

Therefore, IMV, if you're serious about the repair / restoration, then you do need to have at least one such meter in your collection. Allowing these meters to fall into the hands of the "Steampunk" brigade is much a cardinal sin as the hallow tube rapists of old scopes etc.

I must admit that's not been my experience, yes some can be way out, where the older ones used a different type of movement which could lose magnetisation, the later ones are robust. I have some on my bench which are my standard for an analogue movement meter, great for finding peaks and dips when setting up stuff. The later ones are high impedance, which match a Fluke for example. The much older ones such as the Model 7s for example, do slightly load up a circuit, but that's been very useful for working on certain equipment.

[mnementh]

Maybe it's that they simply aren't as usable as a more modern design. The panel markings are small and not clear, and the viewing window of the meter movement is just plain too small and too deep.

At least with my poor vision, the meter movement needs to be as shallow as it can be, and as broad and open as possible to let in as much ambient light as possible such that I can easily see both meter needle and scale.

The core design of the AVO is literally the antithesis of that, so fukkit. 

There are plenty of people out there collecting and curating them; I feel no need to re-iterate that formula myself. I'll just stick with my trusty and easy to read Micronta 22-220... if I ever find it again.

And yes, I know that design-wise, it's a clone of the Simpson 260... but I don't have one of those, so 

mnem

[Squarewave]

A few of the other ones I like are made by Elliot, Windsor. I want a Simpson, so may get one some time if I see one.

[bd139]

Maybe it's that they simply aren't as usable as a more modern design. The panel markings are small and not clear, and the viewing window of the meter movement is just plain too small and too deep.

At least with my poor vision, the meter movement needs to be as shallow as it can be, and as broad and open as possible to let in as much ambient light as possible such that I can easily see both meter needle and scale.

The core design of the AVO is literally the antithesis of that, so fukkit. 

There are plenty of people out there collecting and curating them; I feel no need to re-iterate that formula myself. I'll just stick with my trusty and easy to read Micronta 22-220... if I ever find it again.

And yes, I know that design-wise, it's a clone of the Simpson 260... but I don't have one of those, so 

mnem

The Micronta FET meters are absolutely underrated gems of meters. Decent basic accuracy and flat impedance. Not expensive and surprisingly difficult to fuck up.

I see them as closer to an HP 427A than a Simpson 260.

[Squarewave]

I have got an HP meter somewhere, can't remember the model, I'll have a look later and see which model it is.

[Specmaster]

Maybe it's that they simply aren't as usable as a more modern design. The panel markings are small and not clear, and the viewing window of the meter movement is just plain too small and too deep.

At least with my poor vision, the meter movement needs to be as shallow as it can be, and as broad and open as possible to let in as much ambient light as possible such that I can easily see both meter needle and scale.

The core design of the AVO is literally the antithesis of that, so fukkit. 

There are plenty of people out there collecting and curating them; I feel no need to re-iterate that formula myself. I'll just stick with my trusty and easy to read Micronta 22-220... if I ever find it again.

And yes, I know that design-wise, it's a clone of the Simpson 260... but I don't have one of those, so 

mnem

I don't think that the scale on the Micronta 22-220 is any larger than that of a standard AVO model 7 or 8 and that the meter loading characteristic of the 22-220 is going to similar if not lower than that of most DMMs due to it being FET input meter, where as many service manuals etc do actually specify at a meter of 20,000opv impedance because of the way that meter will load the DUT and thus enable you to replicate correctly the settings that the DUT had when it left the factory

Of course a DMM is easier to read, there is no guessing if the reading is 4.9 or 4.8 etc, agreed, but that reading could be miles away from what it should be due to the lower loading of the circuit under test, basic ohms law stuff, you know it is. 

[m k]

HP MegaZoom Mega-Post!!!

...I didn't have time or energy for that tonight, so I took one for the team and just swapped the CRT neck board over and tried it.




Franken-monitor is no joy; it is not possible to make a CDM-7SF191 serve as a CDM-7SX191 just by swapping the CRT neck PCB. 

Re: the rolling picture with the CRT neck board swap, did you try adjusting the horizontal/vertical hold controls (CRT main board)  & the contrast control (CRT neck board), when you swapped the board to the older CRT?

David

Yeah; it's not a rolling picture, it's only raster and retrace, no video information. The black bar you see there is just a digital camera artifact. I'd have pursued it further, but I was hoping I hadn't fried something with my little experiment, so only powered it up like that a couple times before deciding to pull the plug.

Cheers!

mnem
 

Did you measure any voltages before or after?

Yeah, pins on the ribbon cable of the neck PCB measured similar, except the ones I expected to be different because of TTL vs VGA video. Did not measure anything after reassembling; I wanted to get things buttoned up. As it was, I didn't finish the post until 00:dark:30 ...

If you want we can revisit this later... but right now I have a honey-do list as long my tail. MIL is coming to visit in a week or so. 

mnem
*toddles off to toddle off*

Take your time, MIL-STD can be pedantic.

So if other than data levels are similar there should be something to see.
Maybe there's a wrong data level feedback and cutoff something somewhere.

I've already forgotten from where that wrong H-sync white tube monitor of 54600A schematics was possibly originating but it is very straight forward and without any feedbacks.
Some external voltages there are though, maybe one is only a bit but still enough wrong for shaded neckboard.

BTW,
we are insulating out houses to keep warm.
Seems that other places are about to start the opposite.

[themadhippy]

I found I could often get away with borrowing someone else's.

But then you have the worry about the state you return them.Theirs also the possibility of renting  as needed ,but your never sure of how beat up and used it is ,and you maybe wont get the full service your paying for, so an area ive avoided.

[Specmaster]

Does anyone actually have a Micronta 22-220 meter and would they please measure the scale from end to end across the face of the meter rather than following the arc. Looking at the photos and knowing the physical dimensions of the meter, I really cannot believe that the meter is any bigger as that on an Avo model 7 or 8. I think it just looks bigger.

[bd139]

Maybe it's that they simply aren't as usable as a more modern design. The panel markings are small and not clear, and the viewing window of the meter movement is just plain too small and too deep.

At least with my poor vision, the meter movement needs to be as shallow as it can be, and as broad and open as possible to let in as much ambient light as possible such that I can easily see both meter needle and scale.

The core design of the AVO is literally the antithesis of that, so fukkit. 

There are plenty of people out there collecting and curating them; I feel no need to re-iterate that formula myself. I'll just stick with my trusty and easy to read Micronta 22-220... if I ever find it again.

And yes, I know that design-wise, it's a clone of the Simpson 260... but I don't have one of those, so 

mnem

I don't think that the scale on the Micronta 22-220 is any larger than that of a standard AVO model 7 or 8 and that the meter loading characteristic of the 22-220 is going to similar if not lower than that of most DMMs due to it being FET input meter, where as many service manuals etc do actually specify at a meter of 20,000opv impedance because of the way that meter will load the DUT and thus enable you to replicate correctly the settings that the DUT had when it left the factory

Of course a DMM is easier to read, there is no guessing if the reading is 4.9 or 4.8 etc, agreed, but that reading could be miles away from what it should be due to the lower loading of the circuit under test, basic ohms law stuff, you know it is. 

Actually the whole 20k/volt thing was the only reason Avos were as popular as they were. Literally as you mention the monkeys that wrote the service manuals for stuff with quoted 20k/volt readings made it virtually impossible to use anything else to do any realistic diagnostics. Also to note that most of the older tube circuits were extremely high impedance which is where the 20k/volt thing made sense because the meter loading had significant effect.

What was not required was all the low impedance transistor circuits being specified like that as well.

if you look at the HP service manuals, they don't tend to assume the meter impedance anywhere and the test points and voltage measurements are never at high impedance points without large warnings about it.

[Kosmic]

Ok apparently I won that first lot of transistors 

So for my money I get all NOS (yes I carefully researched all of them first) 1103 transistors, mostly high value and obscure in drawers already

55x 2N3347 - Dual PNP transistors - rare as anything - £8 a go usually
2x 2N3350 - Dual PNP transistors - also rare £8-10 a go usually
10x 2N3420 - NPN switcher - these buggers can blow off 5-8 watts in a TO39
22x 2N3439 - NPN High voltage low fT - ideal for driving CRT blanking / low speed CRT interfaces
16x 2N3634 - Fast PNP switcher that can blow off 5 watts.
199x 2N3640 - 500MHz PNP RF transistor. Fragile.
1x 2N3680 - NPN GP boring
10x 2N3702 - PNP GP boring
8x 2N3705 - NPN GP boring
37x 2N3725 - NPN pass transistor / switch / HF RF PA - nice
10x 2N3729 - NPN dual amplifier - rare as hell - £15 a go
30x 2N3823E black - JFET N VHF amplifier with low 10pA leakage - plastic package
63x 2N3823E white - JFET N VHF amplifier with low 10pA leakage - assume this is the older ceramic package
3x 2N3866 - NPN VHF/UHF amplifier / QRP PA. 800MHz.
12x 2N4209 - PNP saturated switch. Fairly quick
100x 2N4258 - NPN rubbish switch but fairly quick so might be persuaded into RF usage
5x 2N4937 - PNP low noise dual RF transistor (very very rare) 900MHz
22x 2N5014 - NPN 900V (!) switch.
23x 2N5160 - PNP 900MHz VHF RF PA.
1x 2N5055 - PNP fast driver
28x 2N5189 - NPN common low level HF RF PA transistor / SMPS driver
101x 2N5305 - NPN darlington, fast low noise.
350x 2N5401 - PNP very fast high voltage switch
52x 2N5415 - GP PNP switcher boring

Lots of goodies in there and the price wasn't too bad and I can bounce a chunk of the ones I'm not going to use to offset the price

To note I intend to fight anyone to the death on the sellers other lot of transistors 

Edit: some images:





To note that some of the dual ones are suitable for replacing the pairs in old HP and Harrison power supplies as well as designing new circuits

You're going to extract the gold of all those shinny legs right?

[bd139]

Gold? What do I want with gold?



Gold stays on the legs. Going to use the things 

[mnementh]

Does anyone actually have a Micronta 22-220 meter and would they please measure the scale from end to end across the face of the meter rather than following the arc. Looking at the photos and knowing the physical dimensions of the meter, I really cannot believe that the meter is any bigger as that on an Avo model 7 or 8. I think it just looks bigger.

You're missing my point... it is not the absolute dimensions of the movement, but rather the fact they make the viewing window such that almost nothing but the scale itself is visible, and it is all set pretty deep inside the meter case. This drastically reduces the amount of ambient light that gets to the meter face vs a meter with a large, open rectangular viewing window.

TL/DR: The proportionate size of the viewing window is smaller vs the scale; no matter what the actual size of the movement, this will not change.

If you go back, you'll see that point right at the beginning of my original post; you probably just skimmed over that bit.

mnem
 

[mnementh]

Well, fuck-a-doodley-doo... Wouldja lookit what I just found in the bottom of a bin in my MEBBs while looking for a wirebrush...



*cue Twilight Zone dooo-dee-doo-doo music*

IIRC, this is the same meter as the 22-220, only it doesn't have beep continuity. And it is a "fixer-upper" I bought at a thrift store just before I packed everything up for the move in Houston. No idea why it was where it was, except probably end-of-loading-for-a-move exhaustion and the questionable mental state that comes with. 

It is missing a few bits and def needs some TLC... maybe even some 3DP to restore it. 

mnem
 

[AVGresponding]

Ok apparently I won that first lot of transistors 

Oh, so that was you, was it...   

[SoundTech-LG]

I almost didn't grab this before it was headed for trash/recycle. Impossibly rare/unknown/hard to find info on it, but...

https://bama.edebris.com/download/simpson/303/Simpson%20303-3XL.pdf

Great little meter.

[tggzzz]

@tggzzz, my post was not aimed at you in any way, it was in my view expanding and adding to your post and trying to make some form of sense as to why we are suddenly having the moderators popping up and stepping in when in the past we have always as a group been self-regulating and nobody has yet to my knowledge said sod this and has left the group, we continue to flourish and must be a quite a good revenue source for Dave.

Understood, accepted, and even presumed Even if not, my skin isn't very thin

I have no idea how Dave can be making money from my meagre contributions!

[tggzzz]

Ok apparently I won that first lot of transistors 

I wondered if that was you! I considered bidding for the same reasons, but decided I had too much on my plate ATM (I've just found I've spent >£350k, and it will be mine[1] on Monday!). The only ones I considered interesting for myself were the JFETs, and I couldn't be arsed with the others.

Good luck on the next batch!

I've just got 5 each of 27 different voltage zeners for £4, already bagged and labelled. They'll go in a drawer until I need one.

[1] for a loose but usable definition of "mine"

[bd139]

Ok apparently I won that first lot of transistors 

Oh, so that was you, was it...   

Um, yes.

Now I'm going to be all mnementh and sit on my pile of gold and guard it 

[tggzzz]

I bet you're older than me, by quite some margin, but I love Avometers 

Yep, if you drop them, they're donald ducked, though the movements can survive, the casing will be shattered.

I don't love them, and have a couple of carcasses I will unload for a pittance.

Long ago I was working with GPO[1] Martlesham Heath and they told me of a "competition" between Avo 8 salesmen and  a DMM salesman. Everything was evenly matched until the DMM salesman picked up his offering, threw it across the room, and suggested repeating the competition.

[1] no, it wasn't BT for a few years