Author Topic: Metrix OX 2000 digital oscilloscope  (Read 1659 times)

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Offline shakalnokturn

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Metrix OX 2000 digital oscilloscope
« on: April 16, 2018, 09:13:36 am »
I recently bought a couple of these DSO's plus spares, they are 4 channel full digital oscilloscopes with 150MHz bandwidth and 200MS/s (?) sample rate.
Thy have GPIB and RS232 connectivity, internal monitor is a green CRT, there is also a VGA output with non-configurable color for the traces.


I have:

1 repaired skynet PSU.
2 green VGA monitors, only one tested so far.
3 frontend boards, 2 are working with cal. errors, one is beyond repair due to something serious happening on the PSU.
3 CPU/Acq. mainboards, only one tested and appears to be working normally so far.
3 Front panel boards, only one tested so far.

The first aim is to get one fully working scope out of all this before trying to throw a second one together, not an easy task as there is no service information out there.

The F.E. boards are both failing the self test "randomly" mostly for bad offset on most channels but also for bad gain at times on some channels.
I'm suspecting the relays could be the cause for the gain fails although all the N.C. contacts measured a decent resistance so far.

Each channel has:
Two RA12W-K, three A12W-K and one Hamlin (Littlefuse) HE3651A6490 reed relay.
One AD711KR fast OP-AMP
One TL084C
Two SL3227
One SL2364C
One MC14053B
One ULN2003A (relay drive).

There is some time sharing as CH1+CH2 are sent to one ADC (AD9002AJ), CH3+CH4 are sent to another ADC on the acquisition board, there are only 2 ADC's.
I haven't identified where the switching happens yet, the last chunk on F.E. before the coax to the Acq. section is mainly discrete.

Any clues on what to look for and how this could all tie together are welcome!

Scans of the F.E. board here:

https://photos.app.goo.gl/lsmE1pMSz0d0s6Sx2
https://photos.app.goo.gl/vJFXiwfXi71yETf73

 

Offline shakalnokturn

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Re: Metrix OX 2000 digital oscilloscope
« Reply #1 on: May 18, 2018, 02:02:20 am »
BUMP

Still playing around with these, it really looks like the person who sold them threw all the worst parts of a dozen identical scopes together, then threw the scopes on fleabay so I could have hours of fun for a moderate price.

Getting in touche with Chauvin-Arnoux or Manumesure has not helped in any way so far.

All the same I seem to be getting somewhere, although the one I've been working on so far was failing self-test randomly on all channels, it is starting to look like it was mainly out of calibration. The last cal. dating back to 2011.

After many hours of trying to follow tracks around the F.E. board, I have a very slight better understanding of the machine.

I have also dumped the two 27C4001 EPROMS, grouped them as a single 16bit image and found in the text strings that there was a hidden FULL 45" CALIBRATION (!) other than the FAST 5" CALIBRATION in the user menu. (Think SPC on the Tek scopes.)

The point of leaving the 5" Cal. accessible to the user is that these bi*ches drift a helluvalot! Of DSO's of the same era I still find the LeCroy 9300's did best with their automatic re-cals freezing the UI for a few seconds.

Also desoldered, dumped, socketed the M28C64C EEPROM holding the cal. data before finding the way to access the full cal. menu and fooling around with it.

 

Offline shakalnokturn

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Re: Metrix OX 2000 digital oscilloscope
« Reply #2 on: May 30, 2018, 09:24:29 am »
The only documentation I've found on this DSO is the attached commercial overview.

It mentions a 200MS/s rate on CH1, and 100MS/s on the remaining three channels.
I can understand how the acquisition system could be combined to reach 200MS/s when only one channel is used (two AD9002 ADC's are used in here) but no matter the setup the single shot acquisition remains the same.

The brochure also states FFT in the math functions, nowhere in the scope's menu or even searching the ROM dump can I find FFT. Maybe this required another ROM version...

I almost have two working scopes, all I'm missing now is a second PSU of course they are the main failure cause and pretty much unobtainium.

Outputs on the original PSU are rated at:

-16V / 0.7A
-5.2V / 5A
+5V / 3.5A
+14.5V / 3.5A

They all have OCP and possibly OVP.
I have not yet measured actual current on each rail.

I'm either thinking of using a cheap MeanWell 24V PSU (that I already have) followed by independent buck regulation for each rail or re-wiring (re-winding) an ATX PSU to suit the job.
Given I have plenty of repair experience (including SMPS) but little design experience, which option would be more reasonable?
(Unless anyone has a suitable PSU for sale of course...?)

 

Offline shakalnokturn

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Re: Metrix OX 2000 digital oscilloscope
« Reply #3 on: May 30, 2018, 11:45:47 pm »
Here are the real life current requirements for whoever needs to know:

-16V / 0.8A
-5.2V / 4.6A
+5V / 1.3A
+14.5V / 3.12A
Totalling around 90W, that's without PCMCIA card inserted and without using any ports.

 

Offline shakalnokturn

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Re: Metrix OX 2000 digital oscilloscope
« Reply #4 on: June 04, 2018, 10:25:49 pm »
Still updating for the sake of documenting the instrument a little.

The SkyNet AKE-9110 SMPS runs at 60kHz, the primary side PWM is a SK-6080, a custom design from Unitrode for SkyNet. (About the same era there were also similar PWM custom designed by Fuji-Electric with the same SK-xxxx part numbering)

Auxiliary supply for housekeeping is +7.1V from a separate transformer.

Main supplies come as -17.3V, -5.4V, +5.7V, +15,41V before LDO linear regulation using MOSFET's.

Positive supplies share a common ground right from the main transformer, negative windings are independent allowing to use N-MOS pass transistors on the "high" sides of the negative rails before the regulated high side joins the common ground.

Power rails do not appear to have any predefined startup sequencing.

Line trigger output is built around a Sharp PC900V opto.
 

Offline shakalnokturn

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Re: Metrix OX 2000 digital oscilloscope
« Reply #5 on: June 06, 2018, 05:27:21 pm »
People, I'm feeling lonely here!

https://youtu.be/OdqC9nBVFFQ

Oh well I found this video remotely appropriate...  ;D

Here goes a bit of reverse engineering: The line trigger section and the -16V regulation. The PSU has 4 similar regulator daughter boards, the only changes are resistor values to adapt the voltage range. The negative rails have ZD1 in place the positive ones have it shorted out.
I hope I got my schematic right as this is intended to become the reference topic on this oscilloscope.
 

Offline cheeseit

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Re: Metrix OX 2000 digital oscilloscope
« Reply #6 on: June 06, 2018, 06:19:39 pm »
I don't have anything to add but you're not alone so please continue updating as I enjoy reading repair stories like this :)
 

Offline Vince

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Re: Metrix OX 2000 digital oscilloscope
« Reply #7 on: June 06, 2018, 09:36:40 pm »
Hi Paul !   :)

Looks like you have just got yourself yet another challenge !  ;D 

A full blown Metrix DSO without a service manual, as "always" with Metrix stuff... you like a challenge don't you ?!  ;D

I must say I am overwhelmed... you have two scopes and so many spares, I am not even sure I understand what it is exactly that you are trying to fix at the moment ? ... What board, what fault ? Do you have a fully working scope and using it as test bed to fix all your spare boards one by one, each at a time ?!

Anyway, it's late and I most likely should not be reading your topic, seeing as half my neurons are already in deep sleep mode... doesn't help.

I see pictures of the FE board... I also see lots of pesky electrolytic caps !  ;)
I assume you have already recapped that board, and searched real good for any signs of corrosion around all these caps ? Solder joints that look a little bit more dull than the average joint on that board ? I am sure you did... sorry for that  :-//
But on my TDS 544A remember, when it failed again after a year or so, with all sorts of weird and wonderful error messages... it was all fixed just by reflowing a handful of slightly dull looking solder joints on a few passives !  So it really doesn't take much at all to upset these complex boards...

Anyway, just saying that since you don't have any schematics, it's even more vital not to overlook the basics... especially as it might be all it takes to fix that board... simple things first !  ;D

Anyway, I wish you the best of luck, will be following your progress, I want to see the gory details of your fight, and ultimately how you will win ! Because you WILL win ! You always do. Might take a " Minitel " (1) to fix it, but you will fix it, I am sure of that !  8) 

(1) Private joke, sorry !

As for me, I prefer simple things. Look what I just bought last week, a Tektronix 2215, fixed it last night for literally 10 cents, the price of a Zener diode !  ;D

https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1591156/#msg1591156


Keep us posted Paul, don't give up on it , we are all watching your progress !  :)

« Last Edit: June 06, 2018, 09:40:34 pm by Vince »
 

Offline shakalnokturn

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Re: Metrix OX 2000 digital oscilloscope
« Reply #8 on: June 07, 2018, 11:34:08 pm »
Thanks for the encouragements!

I do realise my first post was not that clear...

I first bought one full DSO in good cosmetic state but not working. Seller specified that two transistors were missing on the PSU.
When the scope arrived I replaced the missing transistors and tried to power-up, it was dead. Did a little testing around for shorts on the PSU itself and on the Acq./CPU board where the PSU connects. Nothing obvious.

Looking closely at the brown Nichicons on the PSU there were dull grey solders around, the PSU has many hot spots and the smaller electrolytics were very compact models often squeezed into those hot spots.

Replacing most of them brought the PSU back to life, and the scope powered up displaying the boot splash screen with a distorted picture (monitor problems to see to later...), the traces were not on screen though, shortly after the scope restarted and appeared stuck in a boot loop, I started investigation on the CPU reset (TL7705AC), but before long there was no display at all and the PSU was hiccuping.
Checked for shorts at the PS connector again, nothing too obvious, found the rail that looked lowest and gave it a push with the lab supply. Display came back up, no traces though...

So then I went for a first peek at the frontend board on the down-underside (not far off Australia) of the scope, uncovering there was a nice spluttered burn mark on the aluminium shielding.
That turned out to have previously been a 0ohm SMD on one of the 5V rails, on the underside (getting way down south!) of the frontend PCB same scene, another fused 0ohm resistor.
This one was on the ground though (not something I'd recommend in any design...) I'll never know what the original problem was, but possibly thanks to blowing this ground link, among other-things the AD767 and the P87C52 were gone making any repair hopeless.

I had a quick look for another parts scope and the same seller was selling another in poorer cosmetic condition, missing PSU, fan, but with spare parts: An extra frontend, front panel and Acq./CPU board.
I'm guessing that these two scopes plus spares were the worst parts the seller had left after rebuilding a few scopes swapping boards around.

However, a week later I had more junk to play with and with a "new" F.E. board a scope now showing 4 traces, although 2 are often so far offset that they can't be seen.
From one 5" calibration followed by self test in the menu to the next, the results are not the same.
Things are looking like either automatic calibration failure or self test failure.

From there I checked as many supply voltages and ripples as I could find, basically at all electrolytic capacitors on Acq./CPU and F.E. boards, nothing really worrying, I did hesitate a little at 60mV spikes on a 8V supply, the caps were OK though.

Resoldered the whole worst channel, tested and swapped some relays, things did get a little better, still far from good.

I had dumped the EPROMS right at the start but being high and low data separately for a 16bit SCC68070, they needed to be grouped as a 16bit image before looking for any meaningful text strings. Anyway, a Full 45" calibration did show-up in the dump, so I then desoldered and saved the EEPROM containing the calibration data just in case...

After that I found the way into the cal menus, did a pinch of manual calibration (AD767 reference and frequency compensation on one channel) and let the 45" calibration see to the rest. It does the job by itself, although 45" takes forever....
After that all self tests passed time after time on a warm scope, a cold scope will fail offset on all channels, but I'm guessing that is why the 5" cal was left accessible to the user, to compensate the drift when needed.
(Right, being used to LeCroy this sounds awfully awkward, so I feel I must quote another manufacturer for clarification :bullshit: : SPC is the acronym for Signal Path Compensation. SPC's.  Running Signal Path Compensation corrects for DC inaccuracies caused by temperature variations and/or long-term drift. The benefit of running SPC is that is optimizes the oscilloscope's capability to make accurate measurements based on the ambient temperature.)

So from there I considered I had working scopes, as they were happy with their self-tests and conforming to my own checks.
Note that at the best, DC balance is poor on these OX2000 scopes.

All the monitor took was a good spraying and reajustment.

In the end I don't think I actually repaired much other than the PSU, but considering there is not even a user manual to be found on the WWW, it was a handful to actually look for a way to get at the calibration rather than go round in circles looking for a fault that wasn't there without schematics. (I did a few hours of circling all the same!)

I do like the challenges Vincent  :-/O   (Sorry long post... :-DD)

So now all I need is a PSU for the second scope, the easy way out would be using one of the spare TDS400 PSU's I have around, I/V requirements for each rail are similar enough, they also have the line trigger circuitry, all the same I'd like to see where I get with a modified ATX supply.

That will be later though, for now I have a leaky TDS620 I want to get out of the way before it corrodes through to OZ land, I just hope it won't turn out to need a sacrificial Minitel too.
 

Offline Vince

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Re: Metrix OX 2000 digital oscilloscope
« Reply #9 on: June 08, 2018, 06:21:25 pm »
Wow... loved the story !  :D

Yes, long, but hardly boring, was captivating...

In your first message, I was left with the impression that you basically were facing a huge pile of hopeless junk boards, desperately trying to get anything good out of it...... so in your last message, I was literally taking notes in Notepad, to keep track of what boards you have, their symptoms, what work was carried out.... then in the last few lines, that huge pile of junk suddenly turned into a couple of working scopes, and that you don't need any help any more !  :P

See, I told you you would win ! I just did not anticipate you would win THIS fast  !  :-DD

You are my hero !  ;D

I hope one day, I will be 5% as talented and successful as you consistently are !

Boy, you are giving me the motivation to get back to my TDS 310 !  I blew the hell out of the primary side of the SMPS... will try to rebuilt it (again, no documentation on it, as you know, third party etc etc..). Then if I can find a spare membrane keyboard for the bezel, scope would be fixed...

Do update this topic when you get round to transplanting that TDS400 SMPS, wanna see that  !   ;D

Good luck with the TDS 620... I hope for you that it's not as far gone as "our" TDS 544A !  ;)

And if you ever get your hands on a cheap TDS380 (400MHz 2GS/s), think of me, I want to add one to my ever growing "collection" of (mostly) Tek  scopes   8) Right now, a guy on LBC is selling a few of them, working, pristine, for 250 Euros..  for once it's somewhat reasonable I find.. but I don't have that kind of pocket money right now, sadly... in a year maybe.
« Last Edit: June 08, 2018, 06:29:52 pm by Vince »
 


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