Test Equipment Anonymous (TEA) group therapy thread

[mansaxel]

Why did they put this in the description if they don't ship outside Germany? 

Versand ins Ausland nur mit Telefonangabe !!!
Bieten Sie nicht wenn Sie damit nicht einverstanden sind oder wählen eine versicherte Versandoption.

Translates to; Shipping abroad only with telephone information !!!
Do not bid if you do not agree or choose an insured shipping option.

David

Because I did not read thoroughly enough, thats why! 

[Specmaster]

A company I prevously worked for made equipment that was sold all over the world. Most had IEC power inlets. We used a Seward Supernova or two for production testing. However for some reason the senior manaement decided we could not do our own PAT  So they emplyed a contractor. He came in over the weekend. Amonst otherthings the passed a diecast box withe a IEC inelt but nothing else, not even earth connection, that was on my bench.  They had been told not to go into the R&D section. They alss took all the safety (T earth pin) plugs off the high power lasers. these were only supposed to be plugged ito the door interlocked outlets.
In production they took all the new and bagged IEC leads in stores and tested them. For the EU North American and Austrailian leads they cut the plugs off and fitted 13A ones 
His tester was a battery powered one with no high current earth or flash capability. He didn't get paid........

 

EDIT: It does beg the question though, why the hell wasn't he chaperoned?

Well they would not pay overtime for a competent employee to do the testing so why would they pay for one to watch a contractor? 

It also just highlights the difference between the average contractor and an engineer, especially if said contractor used to be a house basher, then he'd never ever come across such plugs and sockets, equally never come across clean earth varieties either.

Or an old style competent Technician.
These days it's all "monkey see, monkey do"----he probably did a one week course!

"Just last week I cudn't spell teknishun, now I are one!"

A week?  PAT is 1/2 day. at most.
In the UK they brought in a requirment for sparkies working on higher risk  domestic installations to be "Part P" registered. I checked on one of the smaller registraion bodies requirement. It was a 3 day course. There were no entry requirements but "if you have done no electrical work before we suggest you take our 5 day bsic course". You do of couse have to pay there annual registration fee to keep the "qualification". Two weeks from zero to qualified to do any domestic electrical insallation 

Yes, its really stupid, I think it had more to do with making money for the authorities than anything else and also a way of forcing labour costs down for the employers.

I could see the way that my easing out of the company I worked for was engineered, being qualified I was commanding a reasonable wage and my bosses took away my external role and did all design, quotes etc inside, and I was the last person doing the external role, at the same time the owners' son was sent on a 5-week course at the end of which he could do part P and also PAT testing. This was his first and only involvement in anything electrical.

When he passed the final test, he joined the internal team and I was relieved of my duties and given a new role for the company, zero support and over the following year they proceeded to pile the pressure on, so I resigned and retired. So the basic result was that I (with 8 years of training to HNC standards and many years of actual hands-on experience), was replaced by a person with just 5 weeks experience, dubious qualifications

[Specmaster]

No TEA.

Wow, clock those lovely Cossor 1035 or 1049 scopes on their carts, they were proper dual beam as well, not dual trace, they actually had 2 guns in their CRT, and they had their own timebases as well so you could display 2 separate traces of different frequencies and both traces would be locked solid, beautiful machines.

[ch_scr]

[...]
I could see the way that my easing out of the company I worked for was engineered, being qualified I was commanding a reasonable wage and my bosses took away my external role and did all design, quotes etc inside, and I was the last person doing the external role, at the same time the owners' son was sent on a 5-week course at the end of which he could do part P and also PAT testing. This was his first and only involvement in anything electrical.

When he passed the final test, he joined the internal team and I was relieved of my duties and given a new role for the company, zero support and over the following year they proceeded to pile the pressure on, so I resigned and retired. So the basic result was that I (with 8 years of training to HNC standards and many years of actual hands-on experience), was replaced by a person with just 5 weeks experience, dubious qualifications

Only upside: Companys that do this dig their own grave IMHO.

[Vince]

Oh a minter then, great find that some gorilla hasn't been at this one. For sure that adapter has been fitted since early on and preserved the dielectric. 

Picture of the two bottom UHF connector so you can compare. Honestly I do'nt see the point of restoring these scopes unless you also replace all UHF connectors. The old ones look so crusty and ugly, it does not matter how much you clean the face and polish the knobs, the scope will only really come to life visually, once it has good looking UHF connectors. I noticed that when I restored my first type 317.  Unfortunately replacing those UHF connectors is a lot work as you need to remove the face plate which of course requires to take every single element composing the front panel, out of the way. I remember that power switch being a pain. The 317 being very compact makes it all a nightmare. I am hoping my larger 500 scopes will be easier...

As for rework, I take that back ! I just flipped the scope on its side so I can pull the bottom cover and have a look in there... oops !
Nothing massively wrong mind you, but not perfect eitehr. Will need some rework, again, from me this time, to tidy things up a bit.

So what I spotted :

1) Of course the guy put a modern power cable in, but this was done properly, nothing to complain about. Unlike the job that was done on my 575 where the guy clearly attempted to murder me....

2) Guy rewired the primary of the main transformer to accommodate for the higher mains voltage we have these days. You can clearly see that the corresponding ceramic strip is full of flux residue + the jumper is hardly factory looking shall me say ! But what is a bit strange is that his jumper connectzs pin 8 and 3, which is not a valid combination according to the table printed on the transformer ?! 
He should have wired 8 and 1 not 8 and 3. Looking at the schematic for the power supply, using pin 3 instead of 1 make for a higher voltage. Either the guy screwed up, or the other way around he was anal custom wired the primary to try to adjust as closely as possible to his local mains voltage. So would need to wire it properly between 8 and 1 as that's meant for 248 Volts which is what we get around here these days.

3) Next to the transformer, there are a couple small ceramic strips that hold the test points for the power rails (-150v, +100V, +300V and +400V UNREG ).
Strips also hold 3 beefy 10 ohm resistors, which Tek always pus in these scopes, in series with every rail, right after the full wave bridge rectifier.
One of those 3 10ohms resistors, clearly has been replaced with two 27ohms resistors soldered in parallel. Correct type of resistor, power rating less per resistor but since there 2 of them, seems appropriate. Value well... two 27 in // makes for 13.5 ohms instead of 10, close enough I guess he thought. I guess he didn't have a 10ohm at hand and/or not of the proper wattage. The solder joints look clearly how you doing, his iron clearly was not powerful enough for the job... so that would need redoing, with a proper 10ohms resistor as well of course.

This resistor belongs to the 300V rails, which also gives you the 400V UNREG rail. The latter's only purpose in life is to power the primary winding of the HT  transformer for the CRT. I have had this rail fails on several hollow state Tek scope, so I guess that's what happened here as well, hence had to replace this resistor. If I were to remove the shield of the CRT circuit, I bet I would find some more rework/repair in this area as well...

I think the reason this circuitry likes to fail might be because there is a can cap in the CRT section in the upper deck, that filters this 400V UNREG rail. It's voltage rating has not much headroom to begin with, so when you plug the scope today on a 250V outlet, the cap that's already old and tired, sees a voltage that's actually in excess of its rating. But I am not sure it's all the story because there is also a 3.3K resistor in series with the supply, upstream of the cap, hence limiting the current to 120mA which should be plenty low enough to not cause the beefy 10ohms resistor in the power supply to blow.
So I don't know...

Anyway, I know it' s a common failure mode so am not surprised at all to see it here.

This is probably what prompted the guy to rewire the transformer, I would guess....

Which leads to the next question knowing how anal Vince can be......replacement of any/all rusty nuts and bolts ? 

Again there is not rust on this scope so no hardware to replace !    Well other than the UHF connectors I mean.
I have never replaced any screws so far ! I am only considering it strongly for my 575 curve tracer because it's really in a terrible, terrible condition compared to any of my other Tek scopes !  
So much stuff wrong with the 575, some being not fixable within reason/budget/time, that my reasoning is "let's try to improve as much stuff as reasonably possible, hoping it would make the few remaining issues more acceptable".... kind of mindset !  See ?

Obviouslty the nice thing is that the effort I put into researching this screw stuff for my 575, will then benefit all my other Tek scopes potentially, or any other old gear I might buy in the future. So it's not just for the 575.. it's also an "investment" 


Anyway, could not help myself sorry, I powered the thing up, have no variac yet, SUE ME !!! 

Went just fine 

Scope basically works, but does some funky stuff of course, so needs some electrical debugging, most likely as always, a few caps and tubes to be replaced.. but all the fundamentals are good ! 

Cooling fan starts on the button, this alone is an achievement.. I have never managed to get it working properly in my restored 317... so might swap the motors ! 


I can display a signal, trace is sharp and bright, stable, trigger works perfectly, sweep too. Can display the calibrator output. Squares are clean, no undershoot nor ringing. Nice clean square wave. You will I hope appreciate the quality of the screen shot. ZERO reflection, excellent contrast, sharp clean trace... COURTESY of .... well I happen to have a viewing hood for the 317 !!!    Make a world of a difference when trying to take pics of the screen.

I wish I had a hood for my 500 / 5 inch scopes !!!    If I can't find one at a reasonable price, I might try and fabricate one.


What needs fixing :

1) Horizontal amp : trace spans only 50% of the width of the screen.

2) Vertical amp : DC balance out of wack + none of the attenuator settings are good, needs calibrating. Probably just tired 6AU6's again, that make all the attenuation settings out of wack in unison.

3) Now for the really funky stuff that I can't quite explain where it comes from. The trace gets distorted in the following way. It's most obvious when you feed no signal and just display a flat horizontal trace on the screen. So that's what I did. What happens is that when you use the Vertical control knob to move the trace up and down the screen, as you do so, the trace is not horizontal anymore. Instead it develops a "slope", it tilts a bit. The farther away you move the trace from the center line, the more pronounced the slope becomes. If throw the trace to say the upper edge of the screen, you get maybe I don't know, a 25+  degree angle.  The issue is perfectly symmetrical : if you move the trace toward the bottom edge of the screen, it will develop a similar slope, just negative instead of positive.

I can't see how this could be cause by the H or V amps. It's like the CRT is doing it... maybe it got damaged during shipping, the internals of it got bent/out of shape and the beam is not deflected properly anymore. Not a big deal as I have 6 of these scopes so I am sure I will have a good CRT somewhere  ! 
However the fact the problem is 100% symmetrical makes me think, just gut feeling, I am incompetent bear in mind, that it's probably not an internal damage. CRT HV problem ? It's certainly not low nor tired.. .trice if sharp and bright, even when I cranked up the sweep speed. I also had it running of well over an hour and still going strong. Could be TOO Strong maybe ? Could check that cathode and PDA level to make sure it's not too high.
However I am not sure the symptoms are compatible with a HV out of spec...

My best bet is just dirty contacts at the CRT neck connector. Had that in my 575 and it cause not these exact symptoms, but stuff in the same vein where the trace would get distorted depending on where it was located on the screen.

Some pics, then off to go do some work on the house, 3 interior doors / frames to paint. Bought expensive fancy lacquer from my local Pro Tollens paint shop... hoping the result will be worth it !

See you later....

[Andrew_Debbie]

I'm guessing you meant Q3 is a 2N1304 (Ge) and not the 2N3104 (Si), the diagram & parts list both mention 2N1304. 

Oh and a hp 419A would probably be out of budget too, since a certain Carlson did a video on them  , they used to sell for bugger all.

David

Yes - typo.  My fingers aren't used to Ge transistors

[xrunner]

Gah - why do people leave nasty flux all over when they fix things? 

[Cerebus]

On most older dmm high input impedance is only at something like 30V and less depending of the DMM and ranges. My Prema 5017 drop at 10M\$\Omega\$ at 30V

Edit: just checked the Keithley DMM6500, DMM7510, Keysight 3458a, and on the 100V range they drop at 10M\$\Omega\$. I'm not sure it's that common to keep the high impedance input on the high voltage ranges. Electrometers always had a bootstrapped intput amp, so they are able to keep the high input impedance. DMMs on the other hand, normally have voltage divider.

Yeah, designers are only going to do this if ether (A) high input impedance at high(er) voltages is a must for the design (e.g. electrometers) or (B) they already have high voltage rails around to run a bootstrap from so it essentially comes for free.

[med6753]

Some work on the Type 1A1 plug-in. In order to satisfy my compulsive disorder this crusty crapacitor had to go.  So 5uf/150V replaced with new 4.7uf/160V. This will be the only work I get done on this plug-in today. Other non-TE stuff to do but I should be on Discord later today.

 

[Martin.M]

my psu arrived.

[med6753]

And shake up on the torture rack. The Type 321A and RCA scope back on the shelf. Some power up time on the 2465 DMS plus more burn-in on the mini 212.

Saskia, did you get that mini 211?

[Cerebus]

I doubt it's a typo. Easily achieved with a bootstrapped input amp.

Run of the mill spec for decent multimeters nowadays is ">10G input impedance" but they don't specify how much "greater than". In practice it's often in the T region but >10G is all they'll be prepared to guarantee because testing input leakage currents at that level is time consuming and therefore expensive. Measured input leakage current on my 34461A is on the close order of 3-4 pA at 0V (and knowing the architecture, which among other things has a bootstrapped input amp, will be pretty constant and not alter much with respect to input voltage). At 10V that would be  2.5 T .

What did you used exactly to measure 4 pA ?

A good capacitor, specifically in this case a PTFE one. Connect capacitor between HI and LO inputs, short it out, then remove the short. Watch the voltage on the meter rise (or fall) as the capacitor charges from the leakage/bias currents. Pick an arbitrary start point and note the voltage, time until an arbitrary end point and note the voltage then. Calculate:
\[\frac{dV}{dt} = \frac{V_{end} - V_{start}}{t_{end} - t_{start}}\]
and from that calculate the leakage current:
\[I_{leakage} = C \cdot \frac{dV}{dt}\]

It can be a bit rough and ready - you're trying to measure pA without an enclosed guarded test fixture - which is why I'm only quoting a range to one significant figure. It's more of a measured estimate than a precision measurement. With guarding and shielding one could turn this into a precise measurement but for my purposes (just checking the input leakage of my 34461A) it wasn't worth the bother.

Edit: Another reason that this is rough and ready is that you can't account for the input capacitance of the meter itself, it will appear in parallel with your test capacitor. This may or may not be significant depending on the exact internal meter topology and amount of deliberate input capacitance (as opposed to stray capacitance). The input switching on some meters may isolate you from a lot of that capacitance (i.e. capacitance appearing after the input switching may get auto-zeroed on every reading).

[Saskia]

@Martin oh, I got the same one ....

[TERRA Operative]

Will be researching thermal adhesives for Beryllium Oxide. 

Superglue!  
Once it heatsoaks, the thin layer of superglue won't make much of a difference.


Also, not TEA related, but still irresponsible spending of stupid money...  Somehow I got this approved by SWMBO too!
Finally got my new rims delivered today after almost 4 months lead time. Not just chips that are on back order.......
Forged monoblock alloy rims, made with love in Japan with the blessing of the emperor, or something.

[Vince]

Also, not TEA related, but still irresponsible spending of stupid money...  Somehow I got this approved by SWMBO too!
Finally got my new rims delivered today after almost 4 months lead time. Not just chips that are on back order.......
Forged monoblock alloy rims, made with love in Japan with the blessing of the emperor, or something.

Oh boy I would not want to put too much money on alloy wheels, for it's only a matter of time before they get damaged by some kerb when parking, or of course by a tyre shop every time they will have to replace the tires. I did replace an alloy wheel on my car a couple months back... because it was leaking badly, tyre would go flat in a matter of 3 weeks, drove me nuts.  Replacement alloy wheel cost me zero, was donated by a guy from the Safrane forum I frequent. Granted it's all scratched up and looking crap, but not much worse than the other 3 wheel and most importantly... it does not leak ! 

How good it feels not to have to go inflating that tyre every week, not having the handling of the car degrade badly every few weeks, fuel consumption increasing, not to mention the brand new Michelin tyre overheating, deforming, degrading at the speed of light.  Now I can move on and turn my attention to the other issues on the car ! 

Just replaced the cam belt, now need to do the clutch... come spring I think.

[Brumby]

Ah ... I see we have the red valve body and cap.  For tyres that go faster ... right?   

[Saskia]

*sniff* had to let go of my reasonably performing car.

Bye bye kittie  ...

(Jag XKR 4.2 w/ 416 brp and no limiter)

[tautech]

Ah ... I see we have the red valve body and cap.  For tyres that go faster ... right?   

Maybe nitrogen filled although valve caps for that are normally green here in NZ.

[TERRA Operative]

Oh boy I would not want to put too much money on alloy wheels, for it's only a matter of time before they get damaged by some kerb when parking, or of course by a tyre shop every time they will have to replace the tires. I did replace an alloy wheel on my car a couple months back... because it was leaking badly, tyre would go flat in a matter of 3 weeks, drove me nuts.  Replacement alloy wheel cost me zero, was donated by a guy from the Safrane forum I frequent. Granted it's all scratched up and looking crap, but not much worse than the other 3 wheel and most importantly... it does not leak ! 

How good it feels not to have to go inflating that tyre every week, not having the handling of the car degrade badly every few weeks, fuel consumption increasing, not to mention the brand new Michelin tyre overheating, deforming, degrading at the speed of light.  Now I can move on and turn my attention to the other issues on the car ! 

Just replaced the cam belt, now need to do the clutch... come spring I think.

What caused it to leak? I've heard of rims being porous on occasion, or was it the where the tyre seated was damaged somehow?

I've been lusting after these rims for 15 years (since way back when I was a boy racer back in Australia) but had to give up then to save a few $$ to make it to Japan, but now I can have them nothing can stop meeeeeeeee! 

Ah ... I see we have the red valve body and cap.  For tyres that go faster ... right?   

How did you figure out my secret! My minivan (Yes, minivan) needs all the help it can get! hahaha.
Wife wouldn't let me get a sports car because #justfamilythings, so I'm stuck putting lipstick on a pig. It is a nice pig though.

*sniff* had to let go of my reasonably performing car.

Bye bye kittie  ...

(Jag XKR 4.2 w/ 416 brp and no limiter)

A Jag, nice! I was ropeable when my dad sold his XJS without giving me a chance to buy it. 

[tggzzz]

I doubt it's a typo. Easily achieved with a bootstrapped input amp.

Run of the mill spec for decent multimeters nowadays is ">10G input impedance" but they don't specify how much "greater than". In practice it's often in the T region but >10G is all they'll be prepared to guarantee because testing input leakage currents at that level is time consuming and therefore expensive. Measured input leakage current on my 34461A is on the close order of 3-4 pA at 0V (and knowing the architecture, which among other things has a bootstrapped input amp, will be pretty constant and not alter much with respect to input voltage). At 10V that would be  2.5 T .

What did you used exactly to measure 4 pA ?

A good capacitor, specifically in this case a PTFE one. Connect capacitor between HI and LO inputs, short it out, then remove the short. Watch the voltage on the meter rise (or fall) as the capacitor charges from the leakage/bias currents. Pick an arbitrary start point and note the voltage, time until an arbitrary end point and note the voltage then.

Even PTFE capacitors have some dielectric absorbtion. Have you done any calculations to estimate whether that affected your measurements?

Would reversing the capacitor reveal anything?

[tautech]

Oh a minter then, great find that some gorilla hasn't been at this one. For sure that adapter has been fitted since early on and preserved the dielectric. 

Vince's 317..........

What needs fixing :

1) Horizontal amp : trace spans only 50% of the width of the screen.

2) Vertical amp : DC balance out of wack + none of the attenuator settings are good, needs calibrating. Probably just tired 6AU6's again, that make all the attenuation settings out of wack in unison.

3) Now for the really funky stuff that I can't quite explain where it comes from. The trace gets distorted in the following way. It's most obvious when you feed no signal and just display a flat horizontal trace on the screen. So that's what I did. What happens is that when you use the Vertical control knob to move the trace up and down the screen, as you do so, the trace is not horizontal anymore. Instead it develops a "slope", it tilts a bit. The farther away you move the trace from the center line, the more pronounced the slope becomes. If throw the trace to say the upper edge of the screen, you get maybe I don't know, a 25+  degree angle.  The issue is perfectly symmetrical : if you move the trace toward the bottom edge of the screen, it will develop a similar slope, just negative instead of positive.

I can't see how this could be cause by the H or V amps. It's like the CRT is doing it... maybe it got damaged during shipping, the internals of it got bent/out of shape and the beam is not deflected properly anymore. Not a big deal as I have 6 of these scopes so I am sure I will have a good CRT somewhere  ! 
However the fact the problem is 100% symmetrical makes me think, just gut feeling, I am incompetent bear in mind, that it's probably not an internal damage. CRT HV problem ? It's certainly not low nor tired.. .trice if sharp and bright, even when I cranked up the sweep speed. I also had it running of well over an hour and still going strong. Could be TOO Strong maybe ? Could check that cathode and PDA level to make sure it's not too high.
However I am not sure the symptoms are compatible with a HV out of spec...

My best bet is just dirty contacts at the CRT neck connector. Had that in my 575 and it cause not these exact symptoms, but stuff in the same vein where the trace would get distorted depending on where it was located on the screen.

I hope it's not the CRT and IMO more likely the HV grid biasing IME. Old drifted carbon comp resistors is where I looked in the past and replaced heaps of them especially those in M values.
Short sweep can be something similar although checking sweep timing is worth a look at too.

At least it's a runner so shouldn't be too difficult to get right. 

[med6753]

Oh boy I would not want to put too much money on alloy wheels, for it's only a matter of time before they get damaged by some kerb when parking, or of course by a tyre shop every time they will have to replace the tires. I did replace an alloy wheel on my car a couple months back... because it was leaking badly, tyre would go flat in a matter of 3 weeks, drove me nuts.  Replacement alloy wheel cost me zero, was donated by a guy from the Safrane forum I frequent. Granted it's all scratched up and looking crap, but not much worse than the other 3 wheel and most importantly... it does not leak ! 

How good it feels not to have to go inflating that tyre every week, not having the handling of the car degrade badly every few weeks, fuel consumption increasing, not to mention the brand new Michelin tyre overheating, deforming, degrading at the speed of light.  Now I can move on and turn my attention to the other issues on the car ! 

Just replaced the cam belt, now need to do the clutch... come spring I think.

What caused it to leak? I've heard of rims being porous on occasion, or was it the where the tyre seated was damaged somehow?

I've been lusting after these rims for 15 years (since way back when I was a boy racer back in Australia) but had to give up then to save a few $$ to make it to Japan, but now I can have them nothing can stop meeeeeeeee! 

Ah ... I see we have the red valve body and cap.  For tyres that go faster ... right?   

How did you figure out my secret! My minivan (Yes, minivan) needs all the help it can get! hahaha.
Wife wouldn't let me get a sports car because #justfamilythings, so I'm stuck putting lipstick on a pig. It is a nice pig though.

*sniff* had to let go of my reasonably performing car.

Bye bye kittie  ...

(Jag XKR 4.2 w/ 416 brp and no limiter)

A Jag, nice! I was ropeable when my dad sold his XJS without giving me a chance to buy it. 

Let us pray that you are not doing this stupid shit.   

[Saskia]

Looking at a Tahoe now to replace my Expedition

[mansaxel]

Let us pray that you are not doing this stupid shit.   

The best a car looks is when it is stock. Half-witted motorheads who tried to set fire to things in art class rarely have the formal language or the skillset to improve on something made by a professional, and this is proven over and over again by example.

[Cerebus]

Even PTFE capacitors have some dielectric absorbtion. Have you done any calculations to estimate whether that affected your measurements?

The little box of Russian PTFE caps I keep for this sort of thing I've actually tested for DA when I first got them using the usual "soak 'em for days" method and at these kinds of voltages (<10V) the DA is unmeasurable. A quick sanity check is whether you're seeing a linear charging slope or a classic exponential slope - DA rebound has an exponential characteristic whereas leakage currents are typically constant and give a linear slope.

Would reversing the capacitor reveal anything?

In this case no, but in theory yes.