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

[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.