The inside of the green case shows, if you look carefully and know what you are looking for, a 1" gap between the inner frame (and electronics) and the green outer case. (It would be easy to see in a stereoscopic photo, but very few people have suitable red/blue anaglyph viewers to hand!). That gap prevents "unauthorised repair by kicking" or, more charitably, reduces damage when run over by a car. Under the perforated metal grille there are paper bags of dessicant, and there is a humidity indicator visible.
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782814)
Removing the metal box on the top of the guts shows us the battery compartment is clean; maybe the 21.6V 1.2Ah battery will work and I won't have to replace the 18 cells.
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782403)
But then since the battery is from 1981 and last charged in 1982 (yes there is a printed record!), maybe not
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782409)
Anyway, now we can see the interior in all its glory. Shiny.
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782445)
But when we look more closely, it looks like someone has been bodging. Odd heatshrink, jumper leads clipped and with solder blobs. That would be a real pain, since there isn't a manual let alone a schematic.
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782421)
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782427)
But then maybe not, since the bodged jumpers are inserted into dedicated PCB holes and there are other intact jumpers.
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782433)
Looking around at more of the guts, there are the usual blue Philips electrolytics and some wet slug tants. None of them show any leakage. I also find a large 250mA fuse that has blown. I don't have one in my stock cupboard, but there is an intact fuse clipped into the cover.
There's no manual for the 8125A, so for the next steps I have to use the manual for the 8120A, which appears to be a bench DMM rather than a muddy field DMM. Fortunately it is pretty similar in most (but not all) respects.
It turns out that the bodged jumper leads are designed in bodges, a variant of select-on-test components. The ones that have been fiddled with are for the DMM zero, for when the DC zero trimpot isn't sufficient!
So, replace the fuse, turn on, apply a 9V input and .... bingo!
![](https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/?action=dlattach;attach=782439)
The lighthouse has almost disappeared; the bulb limits currents through the NiCd battery. It looks like that was shorted so I removed it, and the current is back to normal.
I fiddle around with the calibration and find that the jumpers that were cut shouldn't have been cut. Typical.
Trying it with 1/10/100k resistors also gives good measurements, and I can't be bothered to try it with AC volts.
So, while not in wonderful calibration, it is certainly working well enough for me be satisfied that I have nixies, and to call it a day. That also means I can ignore recapping and buying NiCd cells.
Since it is military and my house is
full, at least I can legitimately keep it in the garden shed
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)