Test Equipment Anonymous (TEA) group therapy thread

[Brumby]

How hard is it to produce a Lissajous figure on a scope?   

X-Y mode on the scope, two oscillators and play with frequencies, right?  Way too hard for me, it seems.

Scope: BWD 539A ... check
Osc 1: HP 8656B  .... check
Osc 2: Hmmmm....
Advance Instruments J2E - nope.  Last time I checked it only had a level issue.  Now I have to fiddle to get what looks like a 1st and 3rd harmonic of a roughly 1Hz square wave.
BWD 170 Wavemaker - nope.  Well, fair enough - I hadn't checked it since I got it as a rescue.
There's two more for the repair queue. 

What else...?
There's the Wien bridge oscillator I made back in the 70s, complete with bead thermistor - but where the heck is that?
I'd also made a simple transformer based component tester - which was ... somewhere (probably keeping my Wien bridge oscillator company).

Thinking ... thinking ...  (Do I resort to some components and a breadboard??!)

Aha!  I have a Nano VNA and a TinySA - and one of them can produce a signal!  Fortunately, these were close by and I was soon sifting through the menus and found what I needed on the TinySA.

SO (as promised) ... Lissajous on the 539A!:




I really need to get some SMA cables and adapters...........

(Now I can go to bed...)

[med6753]

The longer I let the Type 105 cook the lower the -150V creeps. I did perform an experiment. I have an isolation transformer where I can lower the line down to approx 110VAC and 105VAC. It made no difference. The reference is still out of spec so there is definitely an issue in the PSU that I will address.

[AVGresponding]

Will someone please buy this, so that I don't have to?  https://www.ebay.co.uk/itm/255419336197

[ch_scr]

The longer I let the Type 105 cook the lower the -150V creeps. I did perform an experiment. I have an isolation transformer where I can lower the line down to approx 110VAC and 105VAC. It made no difference. The reference is still out of spec so there is definitely an issue in the PSU that I will address.

Is that a zener or glow tube based reference? At least with zeners, a bit of drift after a really long off time might be normal.
One could speculate reasons for similar behaviour in glow tubes. (Does anyone know?)
A drifting resistor influencing the current through whichever reference device used is also a likely culprit.
I've had glass encapsulated "low tempco" zeners go bad and get become temp sensitive but otherwise working 
(Maybe "just" the zero-TC current changed in that case?)

[Vince]

Wow... didn't think one could write so much about a 3 wire plug !     I don't understand half of it, will need to read it 3 or 4 times I guess.... yes pics would help here.. while you search for them, I will do my own research to figure out what the hell is this " polyolefin " that you are talking about...

Hey, buddy... we don't mind when you get all anal about our knobs, lovingly hand-crafted of PLA and hand-painted to the finest detail we can muster... now you get to hear it about how you fab cables. 

I couldn't find the pics I was thinking of... but I have a extra-long 90° IEC cord that I need but has the GND lug borked off, so here's how I do mine. I'll try and be as detailed as I can, so you can understand not only the technique, but the thought process as well.

Wow..... all these pics, even annotated... I am speechless Dwagon, thanks a lot for the trouble, I sure appreciate !   
That's a very nice little Dwagon that you have become in 2022 !
I am stunned... may it continue tis way !

So the "polyolefin" thing is just the name for the clear type of heatshrink tubing then, OK... I will know what to search for then. I do like the stuff when I see it on terminals on line voltage selector switches, fuse holders, line filters etc, looks professional I find.

[Neomys Sapiens]

<SNIP>

I looked in the parts list but they don't list these connectors sadly ! 
.. so short of getting some from work, if you could if just find some old databook or something to identify them, that would be a big help, I could try and Google for them and maybe with some luck find some for sale. I guess I could salvage a male/female pair from the donour counter, but I would rather try to keep it complete as much/ as long as possible, in case I get the silly idea one day of restoring it.

<SNIP>

Those Hypertac connectors are VERY expensive. Very unlikey to find a cheap set.  They should have part numbers on the connector body though.

They were also made in France by ATI and Sourieau.

[med6753]

The longer I let the Type 105 cook the lower the -150V creeps. I did perform an experiment. I have an isolation transformer where I can lower the line down to approx 110VAC and 105VAC. It made no difference. The reference is still out of spec so there is definitely an issue in the PSU that I will address.

Is that a zener or glow tube based reference? At least with zeners, a bit of drift after a really long off time might be normal.
One could speculate reasons for similar behaviour in glow tubes. (Does anyone know?)
A drifting resistor influencing the current through whichever reference device used is also a likely culprit.
I've had glass encapsulated "low tempco" zeners go bad and get become temp sensitive but otherwise working 
(Maybe "just" the zero-TC current changed in that case?)

The reference is VR tube based (5651). I have one in stock which I'll try swapping but I doubt it's bad. Most likely a resistor has drifted. I will post what I find.

[Vince]

I am feeling brave today !

Got pumped up by the successul "repair" on the little Wavetek, so I decided to up my game and have a go at recapping my Tek 2467B scope who RIFA's turned the scope into a disco smoke machine the other day ! 

Never worked on a 24XX series scope before, so I am learning as I go...  looks not too bad. I think I have got the PSU assembly almost out, did 99% of the work... but it won't come out just yet. Looks like it's kept from letting go, by something really stupid !

There are two wires coming from the lien voltage selector switch that plug onto the board. Need to remove that but access is next to nil !
The terminals are at the very bottom of the board, I can't even get to them with my fingers, never mind with tools !
.. because as you can see the line filter is in the way above the selector switch !
I could remove the line filter but... no, bad idea, because of it's two retaining screws is impossible to get to, PSU is in the way. If I remove that bolt, I will never be able to put the nut back on !
Or.... maybe if I remove the fuse holder that's sitting above the line filter... that would be SLIGHTLY better access to that nut, better hope of being able to put it back on  afterwards... but that's still taking a chance. If I lose the nut, good luck getting it back out the scope ...


Dwagon said he recapped his 2465 some time ago... I guess the PSU design and integration is very similar to the 2467 no ?
Any tips to help me out there ? How did you proceed for these two last wires ?? 

Maybe I got carried away and should not have touched this scope... but it's too late now... I must finish the job, quick, before I forget how to put it all back together !!! 

[med6753]

Vince....go here.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

[Vince]

The reference is VR tube based (5651). I have one in stock which I'll try swapping but I doubt it's bad. Most likely a resistor has drifted. I will post what I find.

Yeah, if a bad tube, I wold rathe rbet on V25 the error amplifier. It's a 6AU6 which is used all over the place in the Tek scopes, in the vertical amplifiers at least, so you should have plenty on hand 

Or a drifted fixed resistor in the feedback network, so that would be R109 / 110 / 112 . Should not take long to measure them up...

[tautech]

The reference is VR tube based (5651). I have one in stock which I'll try swapping but I doubt it's bad. Most likely a resistor has drifted. I will post what I find.

Yeah, if a bad tube, I wold rathe rbet on V25 the error amplifier. It's a 6AU6 which is used all over the place in the Tek scopes, in the vertical amplifiers at least, so you should have plenty on hand 

Or a drifted fixed resistor in the feedback network, so that would be R109 / 110 / 112 . Should not take long to measure them up...

Yep, old carbon comp resistors.... 

[PA0PBZ]

R102.1 - really?

[med6753]

R102.1 - really?

Yep. 

[mnementh]

(...)   You may now critique to your heart's content.

mnem
 

I guess it's more of a critique on the style of plug and less of your technique...
but: in Germany a properly terminated plug is made in such a way, that when excessive force pulls the conductors out from under the screws, the earth wire comes out last, because it is left a bit longer. Seems like in your plugs there isn't even space for that  Apart from that, I especially like the dual heatshrink strain relief and advice on how much to tighten the clamp. 
Edit: Also a professional would use crimped ferrules on stranded wire, but it's the US I guess 

Thanks for the "measured" response.

On a bare-screw terminal strip or "Euro" barrier strip, I can see that.



These types of terminal (the screw terminals on the plug end I used are the same kind) are made specifically for bare stranded wire; the square captive  washer prevents the usual cutting action of a wire under a bare screw, and it self-levels to ensure consistent contact pressure across the entire available surface. When I used to do dB Drags, one of the first things they teach you is to only use bare wires under them, as it makes a mechanically stronger, lower-resistance connection, due to the stranded wire spreading out over a larger contact area. With larger gauge wires, it is common practice to split the strands into two bundles, then twist and trim them such that the strands form two "wires", almost like a fork spade lug terminal. As the captive washer is self-leveling, this maximizes the contact area. I would have demonstrated this practice, but the particular cord used is only 16ga, so not enough strands to split out this way.

On this particular plug end, I suppose there would be enough room to make the GND wire a little extra-long as you suggest... hmmmmm...  What I was taught in school is that it is more important to ensure that pull stress is distributed evenly across all conductors in the event that the strain relief is overcome, to minimize the likelihood of total separation and exposure to bare energized wires. If one or more wires is shorter, it requires much less force, and is much likelier to rip out one wire, then the next, then the next vs all wires at once. This is the principle behind the UnderWriter's Knot, for example.

mnem
Things that make you go "Hmmmmmmm...."

[ch_scr]

R102.1 - really?

Seems to me like they had problems with the current draw - V23 and V24 are parallel'd up series regulators. At one (late) point they realized they'd need a third one...
Solution? R201.1 to the rescue at the 11th hour (I imagine sheet metal, transformers, schematic, etc. are finished already) to pass some current to where it's needed, but not through V23 / V24.
I wonder if there is an additional circuit they had to add that pushed the allowable current over the limit,
or if it was a "purely thermal" problem (maybe like: tubes got more cooling on the bench prototype than in the actual case).
That's all mostly in my mind of course and the real story might be quite different 
Edit: looking at Med's latest picture above, R102.1 does look 15% shoehorned in there, doesn't it?
Edit2: Thinking some more, I guess an additional pass tube would also need filament power, that might be reasonably blocked by "transformers already ordered".
But overheating could also be solved with a series resistor (and without making the regulator less regulaty, unlike the parallel resistor used here).
So I guess the most likely variant is they reached the current limit of V23&V24 (or got uncomfortably close)?

[Ice-Tea]

Cried cawabunga too soon. The 8753 is behaving erraticaly now. I can smell a recappin' in the air.

[mansaxel]

You may now critique to your heart's content.

I won't, not much. 

But,

• I do not think the heating of sheath is proper, so will side with Robert here. Most Cables Where It Matters I deal with are rubber, so point is moot, anyway.  If we're going to use manufacturer catalogues as arguments, my Ericsson Components catalogue, from when they were the ITT Cannon representative, said that if grommet interferes, cut sheath longitudinally and re-seal with shrink toobing. (which makes sense, because the grommet is the main water ingress barrier) And, I really don't see why you could not have made the sheath proper length ab initio. There is oodles of room in that shitty hospital plug.
• Speaking of: All US mains connectors are made of greed, pot metal, paper and brittle plastique. Which is not your fault, and not a critique of you, but it damn sure needs saying. Præterea censeo, Carthaginem esse delendam
• I miss ferrules. They help a lot with not only fit and finish, but also with speed and ease of assembly, and they eliminate AWOL strands. If space is at a premium, there are unisolated ones, that only occupy as much space as the naked copper would. In this particular situation, they would help guide the wires  up to the terminals a bit better.  The Chinesium ferrules from The Bookstore are good enough. The Knipex does them well.
• EDIT: And, the ground wire SHALL be the longest, just as was stated by ch_scr

And, I hardly ever build IEC C13 cables. I have one I've made specially, for the inlet to my UPS. It's a 4m rubber cable, RDOE 3G1,5 | SJOOW 16/3 | H07RN-F, and has a C13 in one end, and a IEC 60309 16A-6h single-phase blue plug in the other end; because I've fitted such outlets under my raised flooring.  Other than that, I make sure I've got a beer crate full of ready-made moulded ones, mostly as CEE 7/7 to C13, but also C13-C14 "extensions" because I've saved a bunch of individually fused 19" distribution strips with C13 outlets from work. They've got Neutrik PowerCon inlets, so are good for 20A distributed load, but usually are run with just a bunch of rack devices like sound effects gear or similar.

[mnementh]

Wow... didn't think one could write so much about a 3 wire plug !     I don't understand half of it, will need to read it 3 or 4 times I guess.... yes pics would help here.. while you search for them, I will do my own research to figure out what the hell is this " polyolefin " that you are talking about...

Hey, buddy... we don't mind when you get all anal about our knobs, lovingly hand-crafted of PLA and hand-painted to the finest detail we can muster... now you get to hear it about how you fab cables. 

I couldn't find the pics I was thinking of... but I have a extra-long 90° IEC cord that I need but has the GND lug borked off, so here's how I do mine. I'll try and be as detailed as I can, so you can understand not only the technique, but the thought process as well.

Wow..... all these pics, even annotated... I am speechless Dwagon, thanks a lot for the trouble, I sure appreciate !      That's a very nice little Dwagon that you have become in 2022 !    I am stunned... may it continue tis way !

So the "polyolefin" thing is just the name for the clear type of heatshrink tubing then, OK... I will know what to search for then. I do like the stuff when I see it on terminals on line voltage selector switches, fuse holders, line filters etc, looks professional I find.

Almost... both kinds of heat-shrink are available in colors or clear; all 3 kinds of heat-shrink on the right side of this pic are polyolefin, the blue battery pack and clear heat-shrink on the left are both PVC.

The difference is whether it is intended to be flexible or not. The PVC heat-shrink is, as I mentioned, the stiff, crunchy kind most commonly used as abrasion-protection & insulation on battery packs. Polyolefin is the soft, flexible kind you used on your cable booty-fab earlier.

As for me being nice... shhhhhhh!!! I have a reputation to uphold. 

mnem
 

[Vince]

Vince....go here.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

Thanks, lots of pics and good info in there ! 

.. except it does not address the problem I posted about ! 
.. your post there make it sound like.. a non-event.
So I guess either you have tools I don't have, or you have long thin agile fingers that I don't possess for sure.
OK, so no dismantling necessary then according to you... just need to... take a deep breath and... try harder 

Dwagon what about your experience ??

[ch_scr]

Vince....go here.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

Thanks, lots of pics and good info in there ! 

.. except it does not address the problem I posted about ! 
.. your post there make it sound like.. a non-event.
So I guess either you have tools I don't have, or you have long thin agile fingers that I don't possess for sure.
OK, so no dismantling necessary then according to you... just need to... take a deep breath and... try harder 

Dwagon what about your experience ??

Could you maybe unscrew the switch and take it out together with the pcb? It's my favorite remedy for soldered in 120V/240V switches...
Edit: And yes, I've scratched my head "how did I take this apart easy the last time" until I've remembered to unscrew the switch 
Some say I had already desoldered the wires...

[mnementh]

Vince....go here.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

Thanks, lots of pics and good info in there ! 

.. except it does not address the problem I posted about ! 
.. your post there make it sound like.. a non-event.
So I guess either you have tools I don't have, or you have long thin agile fingers that I don't possess for sure.
OK, so no dismantling necessary then according to you... just need to... take a deep breath and... try harder 

Dwagon what about your experience ??

Hmmmm... I'll need to look at mine again as it's been so long since the last time. For now, this is the best help I can offer in the meanwhile:

Recapping the 2465. All the RIFAs are gone already. Now what? Get rid of all the PSU elcos? They actually look in decent shape.. What about the ones on the analog board? Do they suffer much? Should they be replaced? Don't look too bad either...

Med has an EXCELLENT article on doing the recap starting here: https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

It breaks the regulator board and inverter board into 2 easily digestible sections in 2 posts. 



Short version: You're going to replace all the electrolytics except the 2 huge blue axials. Also look for the little RIFAs & bead tants shown above and check those diodes (replace them all if any one is open or drastically different resistance than the others) and that resistor to make sure it hasn't shifted value, even if it doesn't LOOK toasted.

I've also attached a well-known .pdf of this service procedure from CondorAudio below; it is the source of the photo above. There are electrolytics on the A5 board that commonly fail causing electrolyte damage; it also has their locations. Capacitor BOM is here.

Good hunting! 

mnem
 

Download the .pdf in the link above; it has a lot of valuable info too. 

mnem
 

[Robert763]

Oh, FFS, C... if you can't trust product application notes made by the manufacturer EDIT: with their name on the bottom, what can you trust?

mnem
 

Leviton don't make cable. Show me a application note from Belden and I might look at it.

[mnementh]

Oh, FFS, C... if you can't trust product application notes made by the manufacturer EDIT: with their name on the bottom, what can you trust?

mnem
 

Leviton don't make cable. Show me a application note from Belden and I might look at it.

I didn't say they did.

mnem
 

[factory]

The longer I let the Type 105 cook the lower the -150V creeps. I did perform an experiment. I have an isolation transformer where I can lower the line down to approx 110VAC and 105VAC. It made no difference. The reference is still out of spec so there is definitely an issue in the PSU that I will address.

Is that a zener or glow tube based reference? At least with zeners, a bit of drift after a really long off time might be normal.
One could speculate reasons for similar behaviour in glow tubes. (Does anyone know?)
A drifting resistor influencing the current through whichever reference device used is also a likely culprit.
I've had glass encapsulated "low tempco" zeners go bad and get become temp sensitive but otherwise working 
(Maybe "just" the zero-TC current changed in that case?)

The reference is VR tube based (5651). I have one in stock which I'll try swapping but I doubt it's bad. Most likely a resistor has drifted. I will post what I find.

You could check the voltage across the voltage reference tube, which should be around 86V, had one fail in my Tek 502.

David

[med6753]

Vince....go here.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

Thanks, lots of pics and good info in there ! 

.. except it does not address the problem I posted about ! 
.. your post there make it sound like.. a non-event.
So I guess either you have tools I don't have, or you have long thin agile fingers that I don't possess for sure.
OK, so no dismantling necessary then according to you... just need to... take a deep breath and... try harder 

Dwagon what about your experience ??

As I recall simply pull the wires off the line filter with a pair of needle nose and the board should come out.