Metex Universal combined test instrument systems/stations - a look inside

[Fraser]

I saw a unit on ebay UK described as an 'S.J.Electronics  Universal Electronics System' selling on a 'buy it now' of GBP50 with free postage. The description peaked my interest and after a quick look, GBP50 was winging its way to the seller 

The unit is in fact a Metex combined test instrument system and these were popular a few years ago and found homes in schools, colleges and home workshops. They were not a cheap purchase at around $1000 but they offered the buyer an 'all in one' test equipment solution for the bench. Specifications were nothing amazing. You got four decent quality instruments in a single box.

The unit provides a 250MHz frequency counter, 2MHz function generator, Multimeter with Capacitance + RS232 logging capability and finally a PSU that can supply 0-30V @2A, 5V@2A, 15V @ 1A. The frequency counter also provides an accurate display of the function generator frequency if required.

All this for GBP50....was it money well spent.....let us see what is inside the big box 

Pictures attached.

[Fraser]

More pics 

[Fraser]

Its actually a very well constructed unit and performs to a decent standard. I have not done full calibration checks but all components appear accurate to hobbyist standards at least.

I liked what I saw and decided to use the unit as a relatively compact multi instrument for use in the house when I just want to do some quick checks on a piece of kit. The seller turned out to be a recycling specialist who is located only 2 miles from my home.....I popped down there today and bought another two of these units for friends who like the design.

I attach the similar Metex 9160 model that is the revised version with an improved frequency counter & function generator.

The schematics for the similar 9150 are also attached.

So was it worth GBP50..... I believe so 

Aurora

[alm]

I've used the similar MS9160. One thing I hated was the loud AC fan, this unit appears to be fanless. Power supply was OK, though not terribly stable. Frequency counter was not bad for its price.

Amplitude of the function generator varied a lot with frequency. The manual actually hints at this. Square and triangular wave were a joke near its max frequency (though the specs claim it can do all up to 10 MHz). I felt like they pushed the bandwidth of the function gen too far beyond the limits of the original design. I considered that it may need adjustment, but I never found instructions or a description of all the trimmers.

DMM was a horrible piece of crap that would take seconds to respond (continuity test was absolutely useless) and was battery powered (too lazy to provide a proper isolated power supply?) and used a standard LCD, which defeated most of the point of a bench meter. The 'advanced' features like min/max, data hold or range hold were infuriating to use, requiring too many button presses (something like 6x function, then set just to enable range hold).

Build quality was quite good except some bodge jobs on the DMM.

Not a bad buy for £50 I guess, the power supply alone should be worth that.

[Fraser]

Hi alm,

As you say, these units are a compromise and the specs will not set the world on fire. I would never have bought one new as I found better individual pieces of equipment on the new or used marketplace that met my needs for less money.

The unit appealed at GBP50 and the fact that it was a relatively tidy 'all-in-one' package appealed for some strange reason. The build quality in my unit looks decent enough but I note your comments regarding the multimeter. If it doesn't fit my needs, it will be going to a new home. These things would be great for students or youngsters starting out in electronics....GBP50 does not go far these days.

If anyone wants a unit like this, here is the auction detail and you can contact the seller direct. He does have more in stock but I have not seen their condition so check first. Mine is in great condition though.


Auction:

http://www.ebay.co.uk/itm/270874526811?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

GBP50  with free delivery and these things weigh about 10kg !

[hacklordsniper]

Im watching one quite long time on local ads (probably more than a year now) but the seller continually asks for 500 $ , great buy!

[Neganur]

Ah nice, I have the MS-9150. Bought it some 14 years ago and still happy with it.
The price back then bundled with the LG-5020 20 MHz oscilloscope, was I think 899 German Marks (= roughly 450 EUR).  50 GBP is a tad much for my taste.
The amplitude of the function generator changes quite a bit when you change the frequency but you can just check it with the scope and adjust.

I totally loved the unit when I bought it.

[mianchen]

sorry for digging the old thread. I bought the same unit for the same seller on ebay uk. everything works except the DMM. it's such a heavy unit, I don't really want to return it, as it might cost quite a bit for the postage. £50 isn't too bad just for the power supply. my real question is: is it worthy of repairing? I've got 3 DMMs, but some times an extra spare one won't hurt. I'm a noob though, I don't know where to start if I want to repair it, but I think it might be a good learning experience. the LCD is not showing anything atm. any comment is welcome. thanks.

[alm]

Stupid question, but did you check the battery? At least in the models I've seen, they were apparently too lazy to design a proper power supply for the multimeter, so they used a 9V battery to power it. It may be just the battery that's flat or missing.

It may depend on the exact model, but as I remarked earlier, the DMM in the MS9160 sucked and was essentially unusable in my opinion. I would only use it if I didn't have any other DMM available or desperately needed an extra DMM. I wouldn't waste any time/money fixing it.

[Dawn]

I maintain a group of 9140 & 9150 units for about 9 years now for a tech school.

 There's a little compartment on the rear, upper, left corner that you have to open and you'll see a DB25 and a slot for a 9V battery. That's most likely the cause and well hidden. It's independent of the power supply. I'm surprised you didn't get it missing that cover. I don't think I've ever seen one that has the cover intact for frequent battery access.

[mianchen]

Stupid question, but did you check the battery? At least in the models I've seen, they were apparently too lazy to design a proper power supply for the multimeter, so they used a 9V battery to power it. It may be just the battery that's flat or missing.

It may depend on the exact model, but as I remarked earlier, the DMM in the MS9160 sucked and was essentially unusable in my opinion. I would only use it if I didn't have any other DMM available or desperately needed an extra DMM. I wouldn't waste any time/money fixing it.

thank you for your fast reply.

I've noticed the battery supply when I took it apart, nothing is showing up on the LCD with a brand new 9v battery. how can I tell this DMM unit is dead or not?

[T4P]

Stupid question, but did you check the battery? At least in the models I've seen, they were apparently too lazy to design a proper power supply for the multimeter, so they used a 9V battery to power it. It may be just the battery that's flat or missing.

It may depend on the exact model, but as I remarked earlier, the DMM in the MS9160 sucked and was essentially unusable in my opinion. I would only use it if I didn't have any other DMM available or desperately needed an extra DMM. I wouldn't waste any time/money fixing it.

thank you for your fast reply.

I've noticed the battery supply when I took it apart, nothing is showing up on the LCD with a brand new 9v battery. how can I tell this DMM unit is dead or not?

Most definitely dead, check the transmissions lines to the LCD with a scope, it's directly connected to the ICL7129

[Fraser]

Mianchen,

A suggestion that may repair your unit 

Remove the top cover. Look at the rear of the multimeter section (directly behind the display). There is a daughter board that is held in place by only one screw. The daughter board PCB interconnect often becomes detached from the main board due to shock in transit. Simply press the daughter board back into place and the meter should work fine again  The Meter power on/off button can also cause this PCB disconnect problem if pressed too hard. A design failure.

Kind Regards

Aurora

[Chipset]

Ah nice, I have the MS-9150. Bought it some 14 years ago and still happy with it.
The price back then bundled with the LG-5020 20 MHz oscilloscope, was I think 899 German Marks (= roughly 450 EUR).  50 GBP is a tad much for my taste.
The amplitude of the function generator changes quite a bit when you change the frequency but you can just check it with the scope and adjust.

I totally loved the unit when I bought it.

Neat, I used one of those for my introductory electronics classes in highschool. My teacher had some less than savory things to say about the fact the DMM was battery powered but we had a bunch of decent quality handhelds anyway. We didn't get to use it a whole lot as the class only covered basics & basic components, we got a new classroom for the first analog electronics class which had better scopes, dedicated function gen & frequency counter and a nice standalone dual linear supply.

[mianchen]

Mianchen,

A suggestion that may repair your unit 

Remove the top cover. Look at the rear of the multimeter section (directly behind the display). There is a daughter board that is held in place by only one screw. The daughter board PCB interconnect often becomes detached from the main board due to shock in transit. Simply press the daughter board back into place and the meter should work fine again  The Meter power on/off button can also cause this PCB disconnect problem if pressed too hard. A design failure.

Kind Regards

Aurora

Aurora

Thanks for the tip. Unfortunately, no luck....

The eBay seller is kind enough to offer return+full refund or I keep the unit and get a part refund. I think I'll take the second offer and maybe hack something into the space of the DMM in the future. An LCR meter comes into my mind...

[Neganur]

The DMM module is fairly easy to repair, do you need the schematics?

[mianchen]

The DMM module is fairly easy to repair, do you need the schematics?

Thanks Neganur!

Could you please send me a copy? or post a copy here so other member can download it? I've tried looking for it online, but all I could find was metex9106, 9105. the DMM module was different.

Thank you very much

[Neganur]

Turns out it's the same file as Aurora linked on the first page, I probably got it from him back then:

https://www.eevblog.com/forum/product-reviews-photos-and-discussion/metex-universal-combined-test-instrument-systemsstations-a-look-inside/?action=dlattach;attach=19367

[mianchen]

Turns out it's the same file as Aurora linked on the first page, I probably got it from him back then:

https://www.eevblog.com/forum/product-reviews-photos-and-discussion/metex-universal-combined-test-instrument-systemsstations-a-look-inside/?action=dlattach;attach=19367

I've got this one, but my machine is using MAX ICL7129 chip instead of the 7106 in the schematic. I'll need to take a good look and see if other parts are actually same as shown in the schematic.

Thanks anyway

[Dawn]

I take it that you own what appears to be a Metex 9150 as I don't believe that you've specifically mentioned the model or brand it's labeled as. Be aware that the OEM models that were made under electronic distrubutor's brand names can be quite different inside even though they appear similar to the Metex stock models externally. Two of the lot that I maintain are branded Elenco while the others are Tenma. The ones that appear to be 9150's vary with the counter and DMM section in features and specifications. I'll see if I can pull the file tomorrow and see if any of the versions I have prints for have a 7129

[mianchen]

I've removed the DMM unit completely out of the case today. When I poked it on the bench with a scope, everything seemed working. Cleaned the contact points of the LCD and the rubbery connector thingy. Balanced the LCD on top of the  connector --- it worked !!!

Because I had to hold the LCD with one hand, I only managed to measure a few resistors 'single handed' -- the results were accurate (well, more or less same as what my other DMMs' reading). At least I've proven that it's not dead.

My problem now is how to make sure the LCD display have good contact with the DMM board when I put them back to the case. I've tried a few times and gave up. It didn't work at all in the case, but worked fine when I took them out and pressed the LCD very hard on to the board via the rubbery thingy...

Any advice?

Thanks

[SeanB]

If you can get a new zebra strip ( or find an old one that will be a fit or can be cut to fit, then that will work. Otherwise place a thin clear spacer on top of the LCD in the area of the zebra strip to press it slightly and reduce the gap and provide better contact.

[mianchen]

If you can get a new zebra strip ( or find an old one that will be a fit or can be cut to fit, then that will work. Otherwise place a thin clear spacer on top of the LCD in the area of the zebra strip to press it slightly and reduce the gap and provide better contact.

Sorry I'd have looked for this thread again and said thank you ages ago. I cut a piece of plexi glass same size but thicker to replace the clear plastic LCD window, and the DMM worked after everything was put back to place! Cheers!

[jucole]

Blimey. hehe I think I bought mine from the same guy!

Amplitude of the function generator varied a lot with frequency. The manual actually hints at this. Square and triangular wave were a joke near its max frequency (though the specs claim it can do all up to 10 MHz). I felt like they pushed the bandwidth of the function gen too far beyond the limits of the original design. I considered that it may need adjustment, but I never found instructions or a description of all the trimmers.

Ah that makes sense; When I gave mine the once over, on the Frequency Gen. the square and triangle waves turned into sine past ~2MHz, I thought it might have needed tweaking but like you say the specs. hint at it.

It's ok for £45 though,  I was doing some 3.3v stuff a while back and the voltage pot is far too course, even with your tongue at the right angle it's a pain :-p

[Dawn]

I hate to bring this old thread up again, but I've run into a bit of a problem with one of the 9150's in the DMM module. Is the DMM subsection inside equivelent to any of the handheld models? Even the 9160 buttons and switch are identical on the panel with similar features. I would guess from the insides being orange/yellow, that the guts originated from a handheld meter. I have the scopeview software that never worked very well with the original meter being too slow. Just wondering if there's either a direct replacement or another meter chassis that can be substituted in one of these.

[jancumps]

The meter is not an exact replacement, but a close sister of the 3640 (although that one has more options like frequency and transitor test).
I have a schematic of the all the modules of the 9150.

[free_electron]

Ah nice, I have the MS-9150. Bought it some 14 years ago and still happy with it.
The price back then bundled with the LG-5020 20 MHz oscilloscope, was I think 899 German Marks (= roughly 450 EUR).  50 GBP is a tad much for my taste.
The amplitude of the function generator changes quite a bit when you change the frequency but you can just check it with the scope and adjust.

I totally loved the unit when I bought it.

i got one of those. mine is a Tenma ... but looks exactly the same

[jancumps]

I've hacked the function generator in mine to get at the sweep trigger and ramp.
That was fun. I can use the trigger to trigger my scope, or the ramp (lin or log) as horizontal signal in XY mode.

[alm]

Neat hack. So the TTL/sync output doesn't act as sweep trigger but is also swept?

[jancumps]

Yes, It is swept just like the 50/600 ohm output. It's a ttl level square wave with the same frequency and duty cycle as the normal output.
The generator has a separate VCF in that can be used to alter the frequency.

[Dawn]

Thanks for the hint on the module. I haven't a clue yet what's wrong besides it's not the batteries, it may even be the zebra strip. I was just wondering about options that I had. I've mainted a bunch of these and their predecessor; 9140/Tenma 72-1005 for about 10 years now. Same power supply problems, and one by one, the veneer failing from an impact on the function generators and the pots failing as well. Both repairable although the veneer/pots are impossible to obtain a replacement from any source, a 2" long, shaft multiturn pot works very well in it's place using the counter and the linear pots with the pull switch in groups of two in a bracket are off-the-shelf replacements from electronic musical instrument repair sources. The function gen boards need occasional alignment as well. I've repaired a few of the older counters in the 9140 pulling chips from F-150 clone GW type counters, I have yet to have experienced a failure with the DMM's. I was given this one because not only is the DMM dead, the power supply's variable section is out which means the '723 is probably dead like usual. I've been in this one before, so that's socketed. I was hoping that there was a direct replacement or perhaps a newer model could be installed as the panel arrangement after the '9140 is the same on the 9150 and 9160. This one is actually a Tenma version 72-5085. I've still own one of their written off 9140's on my secondary bench. It's one of those things you tend to dismiss over individual instruments until you use one. Despite the limitations of the earlier unit, especially in the counter, it usually is the first instrument that I go to before powering up anything on the prime bench because of convenience. I should have the correct docs for the this unit, but since I've never dealt with any issues on the DVM's, I might find a surprise inside of something different.

[tig1]

Hi!!  I'm looking at the Metex MS-9150. Just started restoring old tube radios from the 30's and 40's,mostly am. Will this be good enough for my needs? I was also going to get an oscilloscope.  Thanks!

[jancumps]

I have a 9150 and it's a convenient tool. I thought they were not for sale anymore.

[jucole]

I took out my DMM module to have a look the other day, and took some pics;  this one uses the MAX134 chipset.

[jancumps]

That is completely different than the DMM in my Metex MS-9150. That has a rotating selector and LCD display.
You also mention that the function generator doesn't output a proper square at 2MHz. I attached what the signals look like at te highest frequency on mine when loaded with 50 Ohm coax and terminator.

[Dawn]

Same here. Doesn't look like mine either. The 9170 I've seen photos with either a red or green display. That on also has buttons for direct entry on the function generator and outputs serial info from the frequency counter in some adverts. There was both Metex and UniT making the 9150/9160's with different sets of features every time you seen an advert on page on the net. Both with and without counter/timer functions and 2/10mhz capability, fan mentionion in some and not others, and even RMS metering touted at times in the 9160 and other times not. Some had temp measurement inputs, some don't. I have both the 9140 and a 9150. Mine has the full counter with 3 channels A,B,&C to 1.2ghz, 2 meg upper limit on the gen, and a 4000 count display. Both units are labeled as Tenma from MCM

[jancumps]

My counter goes to 1.3 GHz on channel B. It's a 3 channel counter where channel A is switchable between function generator and BNC input.
The generator goes up to 2MHz.
DMM has capacity, no temp or frequency (although I can make the display show the freq label when I enable the 'DUAL' func in voltage mode - but it doesn't measure that frequency ) 

Action Screen Shot:

[jancumps]

Anyone who has a similar but slightly different version has the moral obligation to post an action shot too.

[nctnico]

They have one where I used to work which has a grey housing. I think these are sold under various brand names. I'm not a fan of these units though. They are big and heavy especially if you only need the function generator part.

[Dawn]

I think I'm being repetitive, but this is one of those odd things that it would make more sense to have separates by logic. Yet, using one of these stations or something similar like a TEK TM-500 series frame populated by commonly used equipment rapidly becomes something you can't do without, if only for the convenience. There's nothing in one of these boxes that I don't have a high end, lab quality separate, but it's my choice go-to box for the power supply and DMM before I reach for the big guns. The frequency counter has a TCXO in it and is quite accurate, so unless there's something I really need beyond 1.2ghz or timing function and need my Keithley or HP service monitor, this suffices for the run-of-the-mill frequency counter. Same with the function generator. When I do use it, it's typically for a test tone. I have a 10mhz DDS unit, low distortion audio generators, and an assortment of specialized signalling generators for communications that can provide the same function. The little Rigol DSO, Simpson 260, and this station is generally enough to tackle most repairs. I've even added a simple signal tracer to my older one that functions both as a substitution speaker and a general purpose amplifier for added versatility. I haven't done that to the newer one, but it gives you the idea of how much utility a little unit like this can have as an integrated unit. No sense in being an equipment snob and blowing it off any more then discounting a full featured service monitor in the place of separate bench components for RF. This is about convenience more then precision that in 99% of the time is sufficent for most tasks.

[jancumps]

This matches my experience.

(Except that I don't have the high end separates )

[jancumps]

I just saw that our member free_electron has the same one
http://circuitcellar.com/community/workspaces/a-prolific-engineers-two-bench-workspace-in-silicon-valley/

[pxl]

It is (was) the freq. generator part. The output was connected to an old analog scope (1Mohm). It was ok for about 5 mins then it smoked. The schematic is from these topic (thanks ), however, it is for 9150, it is about the same, not entirely, though.

Any thoughts what could happened? I plan to repair it, of course.

[jancumps]

No idea of what happened. It looks as if someone has revised it before. My kit doesn't have any of these long leads and strange solder joints like you have in your photo of the copper side.

[pxl]

Well, it worked well before I connected my old scope, so I guess, probably this killed it. My assumption is that it was particularly the input impedance of the scope, which is 40pF. Probably this, pairing with the high output + high freq (1MHz) + square wave was too much load for these small resistors.

[buenavista]

I have Metex MS-9140, and DMM does not work normaly. With EEPROM in socket he wont turn ON, but when I pull out EEPROM DMM turns ON but it can not be used because it shows values that have nothing with measuring values.
Do anyone of you have EEPROM dump of this Metex unit?

[Hydrawerk]

There was also an updated version MS-9170. It was good back in 2005 or so. But only the DMM was improved.

[Hydrawerk]

You need an external 9V adapter to use the DMM. That is very strange.

[nctnico]

I have Metex MS-9140, and DMM does not work normaly. With EEPROM in socket he wont turn ON, but when I pull out EEPROM DMM turns ON but it can not be used because it shows values that have nothing with measuring values.
Do anyone of you have EEPROM dump of this Metex unit?

A first try could be to install a new EEPROM and see what happens.

[buenavista]

Do you mean empty EPROM?

[t1d]

Yep, I know this is a really old thread. But, it is one of the very few about this unit.

In another thread about the device (on EEVBlog, IIRC,) I posted that I have various files about it... Schematics, etc., that I have gathered... And, that I would be glad to provide the files to anyone that will send me a private message with their direct email address... This forum's email service does not accommodate attachments. Note: My files contain the information from this thread... The Function Generator hack... The photos of the inside of the unit (But, not just face shots.) ..and other threads.

To be clear, the files do include the seven page schematic for the 72-1005 model. It was graciously provided by MCM Electronics.

However, you should go through the files and make sure that I have provided everything from the thread that you would like to have. I make no guarantees of the content, or that I missed something.

I have also reached out to JanCumps and Dawn to ask questions about Jan's hack and to Dawn for general maintenance advice. I will say that I never did hear from either of them... Not to find fault, but to say we would all very much like their expert help.

I am presently troubleshooting the voltage offset of the function generator. I may post a separate thread about that. If I do, I will post the link, here.

Update: 01/18/21 I continue to receive requests for my files. Accordingly, I set up a GitHub repository, to make it easier to download. I also posted a separate thread, with the address, to make it easier for search engines to find. Here's the GitHub link: https://github.com/TeeOneDee/Tenma-72-1005 Let me know, if the link does not work; I am a GitHub noob.

[MKK]

Hello,

I got a MS-9140 really cheap but the DMM shows no sign of life at all (the rest is all good). While debugging it I found a weird bridged IC near the power feed, see image attached. There are indications of rework here and there, so this might be a fix of sorts?? If so, I can't really understand it.

I've seen photos of the backside of the board in this thread but not of the front (where the user buttons are mounted). Does anyone happen to have a front side image? I wonder if this a production thing... Seems strange...

I cant seem to find a schematic either. The ones I've seen (in this thread only I think) match my unit in all regards except the DMM. Any help is much appreciated!

[t1d]

It has been a long while, since I researched my unit. But, as I recall, the DMM in these units were a direct copy of the hand-held DMMs that they were manufacturing at the time. In my unit, that circuit duplication extends all the way back to the power supply for the DMM. The power supply is a 9V battery clip/compartment. lol  Maybe using a battery was to isolate the meter from the DUT, for the sake of beginner user safety. Or, maybe it was just cheap and easy. So, research their hand-helds, too.

MKK, whatever information that you find, please deposit it somewhere that it can be found easily.

I am getting old enough to start clearing out some of my gear. I might be interested in selling my unit, to a person that would love it as much as I do. Yes, I could donate it, but I am looking for a better home for it than that. It needs love, too. lol. For purchase inquiries, just send me a Private Message with a legitimate dollar amount. Shipping/pick up is from USA/36619. Yes, I know I could post it in the "For Sale" section. Too old to bother?

[MKK]

It has been a long while, since I researched my unit. But, as I recall, the DMM in these units were a direct copy of the hand-held DMMs that they were manufacturing at the time. In my unit, that circuit duplication extends all the way back to the power supply for the DMM. The power supply is a 9V battery clip/compartment. lol  Maybe using a battery was to isolate the meter from the DUT, for the sake of beginner user safety. Or, maybe it was just cheap and easy. So, research their hand-helds, too.

MKK, whatever information that you find, please deposit it somewhere that it can be found easily.

I am getting old enough to start clearing out some of my gear. I might be interested in selling my unit, to a person that would love it as much as I do. Yes, I could donate it, but I am looking for a better home for it than that. It needs love, too. lol. For purchase inquiries, just send me a Private Message with a legitimate dollar amount. Shipping/pick up is from USA/36619. Yes, I know I could post it in the "For Sale" section. Too old to bother?

That makes sense, thanks for the tip! I'll do that.

An earlier post in this thread pretty much sums it up. He compiled what he had available on github https://github.com/TeeOneDee/Tenma-72-1005. There are other schematics in the thread, for sister models. They apply in part to the 9140 as well. The DMM seems to basically be what differs. In my case, the DMM schematic on the github is closest but not quite. It appears there is also some kind of APO not found in the schematics.