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

[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?