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.