Test Equipment Anonymous (TEA) group therapy thread

[Vince]

Function FIRST, I collect TE not hand bags, they are pointless if they don't work properly.

Appearance second, making it look as good as possible WITHIN REASON.
What's "reasonable" is of course defined by my own self, so varies from person to person.
It also fluctuates over time, experience and knowledge.
Some things that used to bother me, don't bother me as much any more, like dents and scratches on a face plate or cabinet.
OTOH things that I thought were a lost cause, out of my reach, are slowly feeling more and more like something I will make an effort to improve. Like metal work to straighten some bent parts, remove corrosion on cabinets and panels, and repaint/refinish. Replacing rusty and missing screws as well. Making leather handles for the old Tek scopes is also tempting me more and more.
Recreating missing metal parts as well, thinking of my Tek 575 curve tracer here.

There is no rule... some things bug me so I try to do something about them, some are too hard and/or expensive to fix so I just give up and live with it... I just adapt to the situation at hand, mood of the day and budget ! Every piece of TE is a particular case ! 

[McBryce]

Anyone looking to add a "screenshot" option to their Tek 400 Series? https://www.ebay.de/itm/115332266476

McBryce.

And surprisingly you can still get the B/W film for the camera. No, not interested.

?? I thought that slot on the side is for an SD card!! 

McBryce.

[mnementh]

@zucca

Don't you ever sleep ?

When I was little my mom was responsible to turn the light off, now at night it is just me and my shit in my lab (wife and kid are in sleep mode).
Quoting one of my favorite writer, I am again the biggest problem in my life....

Chesterton was very much about the big picture, and wrote to describe what he saw in that picture with eloquence and detail (even when the subject of the moment is the smallest, most personal thing), something I strive to do in most aspects of my life.

For those who might be interested, the text of "What's Wrong With the World" is here: https://www.gutenberg.org/ebooks/1717

A bit dated in flavor, but still relevant in context. 

mnem
 

[mnementh]

Function FIRST, I collect TE not hand bags, they are pointless if they don't work properly.

Appearance second, making it look as good as possible WITHIN REASON.
What's "reasonable" is of course defined by my own self, so varies from person to person.
It also fluctuates over time, experience and knowledge.
Some things that used to bother me, don't bother me as much any more, like dents and scratches on a face plate or cabinet.
OTOH things that I thought were a lost cause, out of my reach, are slowly feeling more and more like something I will make an effort to improve. Like metal work to straighten some bent parts, remove corrosion on cabinets and panels, and repaint/refinish. Replacing rusty and missing screws as well. Making leather handles for the old Tek scopes is also tempting me more and more.
Recreating missing metal parts as well, thinking of my Tek 575 curve tracer here.

There is no rule... some things bug me so I try to do something about them, some are too hard and/or expensive to fix so I just give up and live with it... I just adapt to the situation at hand, mood of the day and budget ! Every piece of TE is a particular case ! 

Like I said, man...  It's a compliment.

I'll drop it now... I didn't mean to make a big thing out of a couple stoopit little coils of wire. 

Cheers!

mnem
 

[tggzzz]

Mouser sells 1000ppm/C thick film resistors. SMD, so you'd have to take account of heat dissipation.

Wow... incredible ! I will look into that then, see I can find them locally and with the right value.

If you do stick in a modern voltage ref, they can drift a lot in the first few weeks. IIRC I saw 1mV in 5V in one example (5.0005 -> 5.0015V)

Change of plan, Robert prefers to keep the old Zener and its quantum patina, and instead use a current source to stabilze the Zener, then I don't need 1050 tempco resistors anymore, just regular precision resistors with low tempco.

I'd have thought it was quick and easy to have a hack at the existing resistors, even if there is only a 10% chance of them working.

If not, I would try to get the right tempco resistors, since that probably balances out the tempco of the diode. But first I would work out the power dissipation, since the SMD resistors are smaller and will get hotter.

Alternatively, just use ordinary resistors and accept that the Vref tempco will be out of spec.

[TERRA Operative]

Yellow heatshrink will make those resistors look almost factory fresh if they do get repaired.

[Robert763]

   

Hi Vince,
I would NOT replace the zener with "modern" reference. The well aged zenner is likely much more stable than most modern references. There are a number of high prformance meters that use this type of zener reference.
Keeping a constant current through the zenner is more important.  The current in the existing design is about 7mA
A LM317L and 180R (178R if you want to go to E48) resistor in place of the existing 820R resistor would do the trick. Replace the "special" resistors with standard metal film ones.
The 317L circuit is: output pin and one end of 180R to the -12V suply, other end of 180R to Adjust pin, input pin to the zener anode.

There is a significant flaw in the design of the "test" circuit of this meter. You can't use a voltage derived from the meter reference to test the meter accuracy. The voltages will be ratiometric. So if the reference goes down the so will the test voltage. This makes the test meaningless in terms of accuracy checking.

Robert -

You evidently missed it in one of V's later posts... there is a completely isolated, dedicated Vref just for the test voltage. It just happens to be on the same PCB.

The one he was talking about replacing was this second Vref; I believe he fully intends to repair the circuit in the main Vref, as he has not damaged the temp compensating resistor for that ckt.

mnem
 

I don't think so. There apperars to be a single 6.2 V zenner biased from -12V and with two specified tempco resistors connected to it. One (at the top of tha diagram) feeds the main meter circuits and the other one a preset to give -4V to the test switch. The other Vref he refered to is in a second meter.

@vince, can you confirm if there is one or two zeners in each meter?

[Vince]

Robert -

You evidently missed it in one of V's later posts... there is a completely isolated, dedicated Vref just for the test voltage. It just happens to be on the same PCB.

The one he was talking about replacing was this second Vref; I believe he fully intends to repair the circuit in the main Vref, as he has not damaged the temp compensating resistor for that ckt.

mnem
 

I don't think so. There apperars to be a single 6.2 V zenner biased from -12V and with two specified tempco resistors connected to it. One (at the top of tha diagram) feeds the main meter circuits and the other one a preset to give -4V to the test switch. The other Vref he refered to is in a second meter.

@vince, can you confirm if there is one or two zeners in each meter?

Yes you are right Rob. The schematic posted earlier is all there is to it. One Zener but two "taps"...
Sorry if I confused the Dwagon when I said there were two "references"... I meant two outputs which each serve a completely different purpose and don't interact, but of course as the schematic shows they stem from the same single 6.2V Zener.

Communication is a difficult skill... 


Anyway, just powered up the meter for the first time today... bad idea : doesn't work any more ! 
It looks like all Nixie tubes are counting relentlessly, they never stop... obviously this is controlled by the comparator board which generates the "gate" signal for the counting. So I swapped that board and ... works again. Better yet : the 50V and 500V ranges which were last night as I said, completely out of whack, now appear to be reasonable ?! How can that be.... how is this board concerned with ranges... it's the attenuator board that's supposed to handle that...
This meter is confusing me 
The manual is not good enough to help me as much as it could.. there is no detailed block diagram, not enough detail in the theory of operation chapter, and the schematic is a bit messy, hard to see the structure inside that comparator board, or even the attenuator board either really. None of the signals / wires are labelled, other than the power supplies. It's just a bunch of discrete components thrown on a piece of paper with spaghetti wiring everywhere. It's hard to understand in detail what signal is what, where it goes and how the circuitry is organized 
There is n,o board layout either, and on the board none of the components are identified ! Good luck Vince !

But clearly I need to concentrate on the comparator board, the heart of the instrument. Need to try to make sense of the schematic and try probing around.

What annoys me is that the polarity Nixie also stopped working on the GOOD board... weird. Did I do something wrong when swapping these boards... did I short or damage something... 

Lots of work left to do on this meter for sure !!!

[mnementh]

Sorry, my misunderstanding. When you said the schematic wasn't exactly right, I thought you had determined that there were in fact two separate reference circuits. If they both derive from the same zener, then yes of course the results will be ratiometric, exactly as Robert said.

mnem
 

[Vince]

I'd have thought it was quick and easy to have a hack at the existing resistors, even if there is only a 10% chance of them working.

I will send it to you !

People keep saying I am anal, yet people keep insisting on me fixing a resistor when I keep saying no.
But I am the one being anal ?! 

Stop insisting or I may well give it a try just for fun now !

If not, I would try to get the right tempco resistors. But first I would work out the power dissipation, since the SMD resistors are smaller and will get hotter.

10 Watts should do it, 150 quid a piece 

[mnementh]

*currently shopping sutures on Amazon because I can't find small curved needles to fix a leather chair...*

So I picked this easy chair up at the Thrift for me and my dad to use in the living room; crazy cheap because there's a fault in the mechanism that makes it jam up once tilted back. While not the best furniture, it's still half-decent quality leather (1.2mm or 3oz), and nowadays even "panel-cut" leather still costs thousands in this size, which is both big enough for my fat dwagon arse and feels very solid underneath it. Not a thing that happens often.

Anyhoo... when I took it apart to fix the mechanism, I found one of the stay wires in the seat had worked loose (now fixed) and made this hole in the side of the base; while not visible yet, if I leave it alone it will be, and I feel this chair is worth a little work. Some coat thread, a patch cut from some castoff slacks, and these smallish (25mm dia arc) curved needles which just arrived, so down to work. We'll see how it all turns out in a bit.

mnem
*makes mental note to look for some saddle soap online*

[mnementh]

I'd have thought it was quick and easy to have a hack at the existing resistors, even if there is only a 10% chance of them working.

I will send it to you !

People keep saying I am anal, yet people keep insisting on me fixing a resistor when I keep saying no. But I am the one being anal ?! 

Stop insisting or I may well give it a try just for fun now !

If not, I would try to get the right tempco resistors. But first I would work out the power dissipation, since the SMD resistors are smaller and will get hotter.

10 Watts should do it, 150 quid a piece 

mnem
150 quid apiece...? Are you including tggzzz's "Consultancy Fee" in that...? If so, don't forget the dwagon's slice of the action... 

[cyclin_al]

Anyone looking to add a "screenshot" option to their Tek 400 Series? https://www.ebay.de/itm/115332266476

McBryce.

And surprisingly you can still get the B/W film for the camera. No, not interested.

I wonder if there is a way to mount a CCD sensor inside that?  You could then get digital imaging and keep that nice retro hardware.

[Cubdriver]

Anyone looking to add a "screenshot" option to their Tek 400 Series? https://www.ebay.de/itm/115332266476

McBryce.

And surprisingly you can still get the B/W film for the camera. No, not interested.

I wonder if there is a way to mount a CCD sensor inside that?  You could then get digital imaging and keep that nice retro hardware.

Unfortunately, I don't think so - at least not without changing the lens.  The image plane is the film face, so unless you change the lens focal length you'd need a sensor the same size as the film is, and given the price of medium-format digital cameras, I don't want to even think about how much something like that would cost. 

I agree that it would be pretty cool to somehow rig a digital scope cam in the original camera body, but just can't easily think of a way of practically doing so.

-Pat

[McBryce]

Anyone looking to add a "screenshot" option to their Tek 400 Series? https://www.ebay.de/itm/115332266476

McBryce.

And surprisingly you can still get the B/W film for the camera. No, not interested.

I wonder if there is a way to mount a CCD sensor inside that?  You could then get digital imaging and keep that nice retro hardware.

Well the analogue camera is big enough to fit an entire compact camera inside plus some more, so I don't think that should be a problem.

McBryce.

[ch_scr]

Anyone looking to add a "screenshot" option to their Tek 400 Series? https://www.ebay.de/itm/115332266476

McBryce.

And surprisingly you can still get the B/W film for the camera. No, not interested.

I wonder if there is a way to mount a CCD sensor inside that?  You could then get digital imaging and keep that nice retro hardware.

Well the analogue camera is big enough to fit an entire compact camera inside plus some more, so I don't think that should be a problem.

McBryce.

With a slight 3d printed attachment it could be a smartphone holder that also images the CRT

[mnementh]

...Some coat thread, a patch cut from some castoff slacks, and these smallish (25mm dia arc) curved needles which just arrived, so down to work. We'll see how it all turns out in a bit.

mnem
*makes mental note to look for some saddle soap online*

   

Ehhhhh... I was off to a good start; had some nice even stitching going up until right around the shredded leather at the panel seam. By the time I'd gotten that mess pulled together, hands were so stiff I could barely hold the needle.

Fuck, getting old ain't for wussies.

At least it won't be visible.    I hope my pieces-parts arrive sometime soon, I'd like to get to work on the mechanism.

mnem
 

[tggzzz]

So, place your bets...

I'm going to a small country hamfest this weekend. Will it be

• deserted: fear of covid, crusty hams become "silent key"
• seething: pent up demand after 2 years

I'll see, but what's your guess?

[Vince]

My bet is deserted due to people losing interest in ham over the years ?

If you find an old glowing Tek scope there, please rescue it !

[mnementh]

My guess: 2 actual HAMs, the rest of the occupied tables operated by various different entities flogging the same exact household and makeup wares from the nearest Freight-reclamation liquidator.

And one crusty old bastard selling crusty-ass and broken hand-tools for more than they cost new; may or may not be the same person as one of the two actual HAMs.

mnem
 

[factory]

Seemed plenty of people at the two local sales I've been to this year, picked up a few items of TE at the first one and the Tek 422 at the second one, the seller was reluctant to sell it as it wasn't working, but later on I managed to buy it.

Vince, the Rochar DVM, is it possible the range switching problem was just dirty switch contacts, I noticed it has relays for the auto ranging too. I also find the diagrams quite confusing. They provide waveforms measured at numbered transistors, but you found no layout or markings.
Something I just noticed is some pages indicate Rochar were part of Schlumberger.

The comment I made about trying to repair the resistors was because I've seen Shango066 occasionally repair radio/TV coils, that have suffered corrosion where the wire is soldered to the pins, this was often caused by poor storage conditions, battery leakage, or flux residue. I guess the resistance wire could be much harder to solder anyway, I wouldn't worry about it now it's temporarily fixed, but look at the other problems first.

David

[med6753]

So, place your bets...

I'm going to a small country hamfest this weekend. Will it be

• deserted: fear of covid, crusty hams become "silent key"
• seething: pent up demand after 2 years

I'll see, but what's your guess?

What is the British equivalent of Hobos?

Here it would be a bunch of shabby dressed Hobos sitting around drinking coffee and eating donuts.

So over there (Blank) sitting around drinking tea and eating crumpets? 

Seriously, I suspect you might be surprised at the large size that attends.

[tggzzz]

The ham lifestyle is on the decline, for sure.

I've never seen makeup wares, and doubt that a ham/hobo/tramp would know what to do with them! I've never seen end-of-line stuff at hamfests, only at computer sales.

The stuff I've seen in the past is a random collection of decent old stuff, some new small accessories, and some forgotten things scraped off the attic floor. Plus the odd silent key sale.

I have too many scopes, so it would have to be a very unusual one for me to buy it!

[factory]

Some ebay items that might be of interest.

Not seen one of these with the four channel plug-in for a while, looks in nice condition too, HP 175A scope (in Germany).
https://www.ebay.de/itm/363790727925


I've heard of barn finds (which probably aren't), but never found in a field, quite poor condition bunch of HP 174x & 172x scopes, thankfully too far away for me (in UK). 
https://www.ebay.co.uk/itm/165418915392


Same seller has a Tek Wreck 576, probably too far gone, but maybe a challenge for the brave. 
https://www.ebay.co.uk/itm/165418931698


Someone please rescue this Racal counter from getting parted out, again too far for me (in UK), I did find one a year or two ago, expect lots of bad germanium transistors, I see they had to take the picture of it powered up in the dark too. 
https://www.ebay.co.uk/itm/115331251339


David

[m k]

How much HP 34401A 2W ohms digits usually differ from its outputting measurement voltage?

Now HP says 0,15013 kOhms and Fluke 8505A says 0,14909 V.
Leads are around 0,0001.

BTW,
Temperature dependency of one Volt Ref. AD584-M.
As in room temperature oven with a fish.

0,15 mV / 9,5 C sharp