Test Equipment Anonymous (TEA) group therapy thread

[TERRA Operative]

Just seen that too. https://www.ebay.co.uk/itm/335273185003

David

At that price, I'd buy one stratght away, except the seller doesn't ship to Japan....

[factory]

Do you want me to buy it and forward it to Japan? The LCD is listed at £75.

P.S. the HP item I was looking at in the USA is no longer available, finding an alternative method of exporting TE is still a problem, just not an urgent one ATM.

David

[TERRA Operative]

Ah ha, the front panel is for the LCD version! That's what I'm looking for!
I don't need the actual LCD panel as mine is working great once I cleaned the zebra strips.

If you can buy the front panel and send it my way, That would be greatly appreciated! I have Paypal locked and loaded ready to shoot you the funds.

[factory]

The front panel is ordered, I'll let you know when it arrives here.

David

[TERRA Operative]

Awesome, thanks!

[Vince]

I can only agree with your theory on the leakage, this is usually caused by battery leakage and made worse by the black foam that stores it AGM style.
So when you do scrub it down, make sure you rinse the foam thoroughly.
I once had one of the family so badly impregnated that the battery voltage had caused a char in the foam that I didn't spot at first (black on black) it had me searching for the leakage current once reassembled, the thermal cam showed a hot-spot on the foam.

If you come to needing readjustment I have notes on that, actually the photo might already be around EEVBlog.

Oy !

Leak (electrical and chemical....)

OK so I spent many hours working on the Metrix MX 52 DMM last night and today.

I disassembled and reassembled it way more times than I can remember, and followed many red herrings, but it's finally feeling much better and now put back together for good.

So in the end ShakalNokturn was right.... the gigantic ghost voltage, which also affected the ohms range, was all due to battery leak polluting the PCB.

I did have corrosion on the negative battery terminal, which also locally / partially dissolved the rubber mat that sits onto the PCB and around the terminals.
I cleaned that with 90° alcohol (didn't have any IPA left somehow, need to order some). Looked OK but didn't fix it.
Cutting a long story short, I was eventually led to decide it might be worth trying to clean it some more.
So since I could not trust my eyes to decide if it was clean or not, I decided to go aggressive and use some "mechanical decontamination" methods instead.
I used a fiber glass pen to abrade the surface of the PCB all around the battery terminals, on both sides of the PCB, then removed the contaminated dust using not alcohol but acetone. Told you I was going aggressive this time...
I also used acetone to rub the back side of the rubber mat where the battery terminals are.

Meter now works much better ! 

In Vdc, I now get a solid 000.0
In mVdc I also get 0.000 the moment I switch it on, then there is some capacitive coupling I guess, with the noise picked up (?), and the measured value steadily increases, slowly, by about 0.1mV per second. But of course if I short the probes it zeros out just fine. So good enough for me I guess.

In ohms mode it's much better as well. My precision resistors now read either spot on or close enough to it, be it the lowest value of 390 ohms, or the highest one I have, 50K. So a definite improvement there as well.

The "ADP" mode is not good though, it reads 'OL', or a hundreds of counts, instead of zero, when open circuit. It's basically a 500mVdc range. However the mV range itself, the "real" one, is now working fine, so not sure what's going on....
It still reads fine if I apply a voltage though, or if I short the probes, so it's perfectly usable nonetheless.


Rotary switch

Had to desolder the RF shields top and bottom to get to it 
Luckily the shields were easy to remove, their mounting tabs were soldered only to the surface of the PCB, rather than going through the PCB and be twisted on the other side.
The switch is interesting.... it does not glide over the main board, but rather over a little circular "daughter board" that holds the gold plated tracks. Not sure why they did that... to help with routing the main board ?! 
Anyway, switch contacts and tracks looked clean, but I rubbed them with a Q-tip and alcohol anyway, and the Q-tips were black.... so yeah, there again, even if it looks clean and shiny to the eye... doesn't mean it is actually all that clean.... so worth doing.


LCD

Removed / unplugged the daughter board that holds the LCD and CPU.
Pulled the two zebra strips, cleaned them with alcohol, also the matching pads on the PCB.
Found a trimmer at the back of the board, assumed it was there to adjust the contrast. It does. You can access it when the meter is assembled (bar the back cover of course...), thanks to a hole in the main PCB and another matching hole in the bottom shield.
LCD now works just fine. No weak segments anymore, and LCD now has good contrast when viewed from a normal angle.

Display looks beautiful when out of the case... motivated me to restore the plastic window of the top shell, to remove all the scratches that keep you from appreciating how nice the LCD actually is. It's the first time I try to remove scratches from a display window. I thought this meter could be my guinea pig. It didn't go well at all. Tried sanding the scratches by hand with paper. Starting at 120 grit given how big some of the scratches were, then 180, 400, 800, 1000, 1500, 2000, 5000, magic sponge then car polish.
Problem is that you can't manoeuver the sand paper properly, because the window is so small and recessed. So you have to use tiny movements and you are constantly banging against the edges. Clearly I can't do it by hand. But I will redo the job later with a micro polisher with a tiny 1" backing plate, should work much better.

Cleaning

Well I started with that actually. Took the thing completely apart so I could clean all the bits properly. It's clean now....


CONCLUSION

It works much better now, but I just don't trust it enough to actually use it....... so I think my Fluke 11 will remain my daily driver for now. I bought it 27 years ago but it's still flawless, super reliable. Unlike the Metrix, it does inspire confidence, and has proved itself for nearly 3 decades now.

[wkb]

In general: I don't understand why people try to remove battery leakage residue using alcohol?  In my experience lukewarm water, demineralised if you so prefer, works much better in removing alkaline residue.

Wilko

[Vince]

I used alcohol for general cleaning, removing all the meted/gooey residue from the degraded rubber mat, and general cleaning of the board.
Then I used white vinegar, then rinsed/neutralised with water, then used fined grit sand paper to remove the heavily stubborn corrosion on the negative terminal.

Alcohol because most people have it (IPA) in their lab, at hand, so is a good first step for overall cleaning, removing grease and dirt.
Then as second step, use more specific products for specific problems, like here corrosion.

That's my view anywho 

I think not everybody has demineralised water as handy as IPA, unless you are married and the wife irons your clothes...

[graybeard]

GR874 attenuators from the W6TRW swap meet

[Vince]

Hmmm, I am liking your avatar picture a lot... is that a Tek 575 curve tracer ?! 

[wkb]

I used alcohol for general cleaning, removing all the meted/gooey residue from the degraded rubber mat, and general cleaning of the board.
Then I used white vinegar, then rinsed/neutralised with water, then used fined grit sand paper to remove the heavily stubborn corrosion on the negative terminal.

Alcohol because most people have it (IPA) in their lab, at hand, so is a good first step for overall cleaning, removing grease and dirt.
Then as second step, use more specific products for specific problems, like here corrosion.

That's my view anywho 

I think not everybody has demineralised water as handy as IPA, unless you are married and the wife irons your clothes...

Heh.. I am married, sure, but ironing, hmm. We have a 5 l can of demiwater in the garage, e.g, for topping up my motorbike battery.

Fat & grease and all that fun I attack with alcohol, mineral residue with water, followed with alcohol if required. And, goes without saying, a very thorough drying of the whole shebang.

[tggzzz]

GR874 attenuators from the W6TRW swap meet

I have some GR874 stuff knocking around, some ordinary, some odd. I've only got three pieces of GR874 TE (Philips 200ps/1.7GHz sampling scope, Tek pulse gen, Tek levelled sig gen), so I ought to get rid of the stuff.

One of the T-connectors is a "voltmeter rectifier" containing a 50ohm resistor and Ge diode, useful for detecting envelopes and power. The grey enclosure is marked "50ohm inverter", and I guess contains ferrite-based transformers.

[graybeard]

Hmmm, I am liking your avatar picture a lot... is that a Tek 575 curve tracer ?! 

yes

[graybeard]

More stuff from yesterday's W6TRW swap meet.  Tektronix GR-874 coaxial signal pick-offs-0077-09

1 Tektronix VP-1 017-0073-01
8 Tektronix VP-2 017-0077-01
2 Tektronix CT-3 017-061

[graybeard]

More GR-874 stuff from yesterday's W6TRW swap meet.

custom made made current probe pick-offs and two elbows

[graybeard]

GR874 stuff I already had

The top drawer is opens, shorts, and a load, plus one pick-off
left and right drawers are adapters
the mixed parts are more adapters, an attenuator, a tee, and three insertion units

[graybeard]

More Tektronix GR-874 stuff from yesterday's W6TRW swap meet.

2 Tektronix 067-0555-00 variable attenuators
1 Tektronix 017-086 Pulser

[TERRA Operative]

The only GR-874 gear I have is a Tek 284 pulse gen and a GR-874 to BNC adapter for it.

The nice photos here on Tekwiki are of my unit: https://w140.com/tekwiki/wiki/284


I should sell it, my Leo Bodnar pulser is much more compact and easy to use on my small bench.

[graybeard]

The only GR-874 gear I have is a Tek 284 pulse gen and a GR-874 to BNC adapter for it.

The nice photos here on Tekwiki are of my unit: https://w140.com/tekwiki/wiki/284


I should sell it, my Leo Bodnar pulser is much more compact and easy to use on my small bench.

I had to part with most of my tube based boat anchor test equipment years ago due to lack of space.

[shakalnokturn]

My turn to work on a Metrix tonight:

I received it this afternoon, a MX54 with blue holster sold as not working / for parts, negotiated down to a little less than 30€ shipped.
It came on but no voltage measurement other than the mV range, resistance autorange all over the place, OK-ish on low values, false moving upwards.

Took it apart, the foam beneath the battery was a little oily, main PCB had seen some rework, I took the lot for a thorough scrub with hot water and washing-up liquid. Rinced, dried, reassembled. No better...

After a few measurements I was led to the thin film precision resistor decade divider, here a Vishay CNS 559 that I believe was custom made for Metrix as the whole WWW has no trace of it. 10M resistor is open. Hit by high voltage?

Looking around internet for replacement (there are some models with same values from Caddock / EBG  with differences in pinout) the Thunder resistor TC1746A looks like a drop-in replacement, no idea where to buy it though.
I've decided to swap the network from a MX53 that deserves it less than the MX54, then fit the MX53 with a precision / trimmed value as replacement for the 10M.

[shakalnokturn]

The swap is finished. Left to right:
Sacrificial MX53, MX54 repaired with MX53's divider network, reference meters. Now should I be bothered to do a software readjustment ?

While operating the MX53 out of it's case I noticed the piezo buzzer was ticking slightly, that pushed me to scope the current consumption.
In the end all these meters tick a little, most audible is while in AC or AC+DC modes, once they're reassembles it's hardly audible.

[Vince]

Wow thanks for that, that was a cool repair and experiment ! You only post once a year but when you do it's juicy   

Never noticed the buzzer ticking, but now that you mentioned it I am sure I will start hearing it now, "of course"   

Cool screenshots, what scope is that ? It looks like a combiscope but it does not look like a Fluke/Philips, based on the CRT surround that's a lighter colour on your scope.
I think it would however fit better a Hameg combiscope... is that it ? I quite like them and would not mind one, to enrich my scope collection, but they are not anywhere as plentiful / common as the "regular" Hameg scopes on leboncoin.fr.

Don't say a word, I am sure you got yours for 20 Euros and fixed it in 5 minutes for 50 cents, as per usual. I hate you 

[Robert763]

Bought a Rhode & Schwarz AMIQ I-Q modulation generator on ebay.
Been considering one for quite a while. For those who don't know the unit it is used to generate complex in phase and quatrature signals to module vector signal generators. typically used for things like cellphone signals, GPS etc. Basically a PC driving a pair of high speed DACs. They are "headless" the only control is the on off switch. It basically takes commands over either GPIB, RS232 serial of as a file on floppy disk. There are a couple of status LEDs but that is all.
Of course this one does not work. Appears to boot (runs DOS) but no response to commmands over the serial port. You set the control port and parameters by a file on a floppy disk that it reads during boot. Tried that and it trashed a couple of disks and contaminated the floppy drive I was using to write the file  :roll: A bit of head cleaning later and file appears to being read, control LED flashes if I put a deliberate error in the file. Still no response. So I opened it up. And the PC mother board has capacitor rot. So changed about 15 electrolytics but the CPU fan is siezed so I will have to replace that before doing much more. IT seems from what little service information there is that you can plug a videocard in and get somefeedback. It that doesn't help I'll try booting DOS and see ifthe serial port is OK.
Why am I doing this?  Well I have a R&S SFQ "TV Test Generator" which can take external I-Q modulation making it much more useful as the AMIQ can produce basic analog modulaton as well as complex. R&S have a couple of bits of software to generate the required data for the AMIQ.

[shakalnokturn]

Wow thanks for that, that was a cool repair and experiment ! You only post once a yer but when you do it's juicy   

Never noticed the buzzer ticking, but now that you mentioned it I am sure I will start hearing it now, "of course"   

Cool screenshots, what scope is that ? It looks like a combiscope but it does not look like a Fluke/Philips, based on the CRT surround that's a lighter colour on your scope.
I think it would however fit better a Hameg combiscope... is that it ? I quite like them and would not mind one, to enrich my scope collection, but they are not anywhere as plentiful / common as the "regular" Hameg scopes on leboncoin.fr.

Don't say a word, I am sure you got yours for 20 Euros and fixed it in 5 minutes for 50 cents, as per usual. I hate you 

Well it was an interesting repair as I almost (still thinking I should do the software readjustment if I can be bothered) got the results I wanted with what I had at hand and it didn't involve the usual contamination or dirty switch problems nor unobtainable IC's.

To be fair you really have to know what you're listening for to notice the buzzer noise, no trouble really. It got me worried because I've had Flukes before where the buzzer drive was "shorted" and current consumption was sky high with a still working meter. That and the LCD being a little faint on some segments despite the zebra cleaning made me want to look if I could correlate current spikes with what I was hearing.
Now you know, have you heard it?

You're right it's a Hameg, I caught it on Leboncoin of course, a decent catch at 90€ shipped and working, not worth any hate tough 

It's a HM1508 (First version - no USB) I'm still not sure how long I'll be keeping it... I do like the analog / digital, 150MHz, 1MB, 1GS/s but considering all the hardware is there it leaves me the impression of an incomplete product. It has been the scope getting the most attention for several months now and some of the UI just doesn't feel intuitive for a quite basic scope - but maybe I change scopes too often.
Another deception is the very limited amount of on-screen simultaneous measurements you can display for a scope of its age, I'm forgiving for the mid '90s Fluke / Philips Combiscopes to be limited, not here.

My main grunt is the component tester, my motivation to buy this (other than the price and possibility to make some benefit when letting it go) was to have analog / decent digital figures and the component tester which is something I use a lot. IMHO they completely ruined that:
You cant switch to and fro component tester in one key press, it brings up a menu then 2nd press enables C.T.
Worse you can't zoom x10 horizontally the component tester at all, that's something I like to do regularly when quickly checking electrolytics.

So the conclusion is I need at least: 1 old Hameg for the component tester, the Micsig for the serial decode, a LeCroy for the advanced math and statistics, a battery powered and isolated scope for those rare occasions. (Of course that's a bare minimum, always have some backup !)
Anyone know of a single model that ticks all the boxes?

[TERRA Operative]

Once again I'm starting to think I need a 4263B LCR meter...