Test Equipment Anonymous

Posted: **Thu Feb 13, 2025 5:36 pm**

Finally, managed to buy one from someone who isn't a scammer/ham/fuckwit. Also, today, finally went and picked it up from the Post Office, where it has languished since last Friday.

Firstly, here's some messages that flew back and forth between the seller and myself:

Seller: "Hiya ! Many thanks for buying this classic multimeter - i had nearly 20 other parcels to do today and as this one is a little bit bigger and heavier than the rest I'm finding a decent way to pack it so it will arrive to you in as good as condition as it is today (i.e with all the nixies working) I should be able to ship it tomorrow and Wednesday at the very latest - i will keep you upto date. Thanks again ! "
AVG: "Ok, thanks for the update"
Seller: (pics of the packing process)
"hello there - the meter is in the post I've wrapped it in bubbles, then put in a plastic container box, then wrapped that in bubble then packing material double thanks again for the buying the meter - i hope it is well used, its a lovely bit of historical kit "
AVG: "That's great, thanks. An acquaintance who used to own one said he reckons they are so robust that you could just slap a label on the case and ship it as is, but then he's also known for throwing a Solartron 7075 (in a carry case) on the ground from the boot of his car... I now own that meter and take better care of it! I own two Fluke 8300A's and numerous nixie counters, so I can assure you it will be well cared for."
Seller: "thats made my day ! thank you so much - all funds go towards my research / phd - so you are really helping me out - and i feel really good about the meter has gone to a good home, you obviously know exactly how good they are. Yes, tough as hell, but even then I wouldnt risk it to the post office - its probably survived enough to write a small book about, and now a new chapter begins."

Seems like a nice bloke. Hopefully we see them on one of the forums at some point.

I did make the mistake of dropping my car off at the garage, and then walking to the PO, instead of driving to the PO and picking the thing up and taking it home before dropping the car off...

It's been packed in a plastic organiser box, which I don't expect to have survived:

IMG_20250213_164335446.jpg

IMG_20250213_164926201.jpg

Yep, it's dead, Jim. But it did its job as a sacrificial element, the meter case has just the usual dents you'd expect from being manhandled by monobrow squaddies:

IMG_20250213_165711886.jpg

IMG_20250213_165831159.jpg

No rattling or tinkling, seems all good. And of course I'm just dying to use that power lead and those test leads...

IMG_20250213_165910028.jpg

IMG_20250213_170213837.jpg

Once it's sat for a day or two acclimatising, and I inspect that mains lead, I'll give it some juice and make another post with the results.

Posted: **Thu Feb 13, 2025 6:23 pm**

Nice!!!!

-Pat

Posted: **Thu Feb 13, 2025 6:57 pm**

AVGresponding wrote: ↑Thu Feb 13, 2025 5:36 pm Once it's sat for a day or two acclimatising, and I inspect that mains lead, I'll give it some juice and make another post with the results.

Acclimitisation is robably unnecessary. Mine had a large bag of silica gel floating around the big gap between the meter and the case.

Inspect the mains lead? That's why ELCBs were invented.

Have gloves handy, for when you enter the toxic waste dump, and think of how you are going to dispose of all that yummy cadmium.

Once you have the case open, hope the torch is lit due to shorted NiCds.

Sellers on fleabay claim it is good to 20g acceleration, so it ought to survive without being bubble wrapped.

Posted: **Thu Feb 13, 2025 8:21 pm**

I'd be surprised if a courier broke that even with that shitty packaging.

Nice haul though!

Posted: **Thu Feb 13, 2025 8:48 pm**

bd139 wrote: ↑Thu Feb 13, 2025 8:21 pm I'd be surprised if a courier broke that even with that shitty packaging.

Nice haul though!

Haul indeed; they ain't small!

I got mine for 99p partly because it was badly described, partly "collection only". I drove to the shipyard(!) To pick it up, and he said he got it from somebody (?a ham?) who had bought it as a desk meter - but didn't use it as such.

It isn't a desk meter; it is too big for that!

Posted: **Fri Feb 14, 2025 1:28 am**

Nice! I can't wait for you to post a few pictures of it lit up in action!

Posted: **Fri Feb 14, 2025 2:28 pm**

tggzzz wrote: ↑Thu Feb 13, 2025 6:57 pm
AVGresponding wrote: ↑Thu Feb 13, 2025 5:36 pm Once it's sat for a day or two acclimatising, and I inspect that mains lead, I'll give it some juice and make another post with the results.
Acclimitisation is robably unnecessary. Mine had a large bag of silica gel floating around the big gap between the meter and the case.

Inspect the mains lead? That's why ELCBs were invented.

Have gloves handy, for when you enter the toxic waste dump, and think of how you are going to dispose of all that yummy cadmium.

Once you have the case open, hope the torch is lit due to shorted NiCds.

Sellers on fleabay claim it is good to 20g acceleration, so it ought to survive without being bubble wrapped.

Fortunately the battery had been removed by a previous owner. By and large it works, though it needs a cal and adjust, and digit two stopped working after a few minutes. Do you still have the scan of the 8120 manual by any chance?

Posted: **Fri Feb 14, 2025 2:35 pm**

I've used the 8120 manual, https://assets.fluke.com/manuals/25_27___smeng0000.pdf

See https://www.eevblog.com/forum/testgear/ ... -teardown/ for what not to do. For specific calibration information, see reply 26.

Posted: **Fri Feb 14, 2025 3:43 pm**

tggzzz wrote: ↑Fri Feb 14, 2025 2:35 pm I've used the 8120 manual, https://assets.fluke.com/manuals/25_27___smeng0000.pdf

See https://www.eevblog.com/forum/testgear/ ... -teardown/ for what not to do. For specific calibration information, see reply 26.

LOL dude that's for the 25 and 27 handhelds...

Posted: **Fri Feb 14, 2025 5:11 pm**

AVGresponding wrote: ↑Fri Feb 14, 2025 3:43 pm
tggzzz wrote: ↑Fri Feb 14, 2025 2:35 pm I've used the 8120 manual, https://assets.fluke.com/manuals/25_27___smeng0000.pdf

See https://www.eevblog.com/forum/testgear/ ... -teardown/ for what not to do. For specific calibration information, see reply 26.
LOL dude that's for the 25 and 27 handhelds...

How embarrassing. IIRC I searched, found link, downloaded to check, then re-found the link and posted it. Except clearly I didn't re-find it and I still can't re-find it. History ain't what it used to be.

The manual I have is 38MB, so too big to email or put on this forum. ko4bb is still down, but I'll try to put it on BAMA

Posted: **Sat Feb 15, 2025 9:52 am**

Ooops, meant to upload some more pics. I opened it up to try and find the cause of the failed digit. Ran it on DC from the HP 6633B, and naturally the digit was working. At this point I'm convinced it's either a dry-ish joint, or a slightly grotty pin/socket. I did monitor the temperatures of the 7441 and nearby components, it reached about 40°C, and a nearby diode made it to 38°C. The diode isn't in the 8100A schematic unfortunately, but I think it's part of the inverter.

Overall view of the main board

IMG_20250214_133544920_HDR.jpg

Some of those unobtainium Fluke custom wirewounds

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The input divider is on a daughter-board, unlike the 8100A

IMG_20250214_133708695.jpg

Dual jfet, first stage input amp

IMG_20250214_133735108.jpg

Digit drivers

IMG_20250214_133804728.jpg

The BCD-10 segment decoder/driver

IMG_20250214_133912341.jpg

These big 'uns are on the underside, not divined their purpose yet

IMG_20250214_134110980.jpg

IMG_20250214_134126267.jpg

Overall it's very clean inside, helped no doubt by a previous owner removing the NiCd's from the battery pack.

Posted: **Sat Feb 15, 2025 10:05 am**

tggzzz wrote: ↑Fri Feb 14, 2025 5:11 pm The manual I have is 38MB, so too big to email or put on this forum. ko4bb is still down, but I'll try to put it on BAMA

Apparently it is up on BAMA, at https://bama.edebris.com/manuals/fluke/8120a/

Posted: **Sat Feb 15, 2025 10:15 am**

AVGresponding wrote: ↑Sat Feb 15, 2025 9:52 am Overall it's very clean inside, helped no doubt by a previous owner removing the NiCd's from the battery pack.

Mine was too, even though the NiCds had made their presence known.

For fun make sure you understand the function of Qx/Cx, x=1,2,3,4. It come from the era where people made decade counters from three transistors and a handful of passives.

Posted: **Sat Feb 15, 2025 1:21 pm**

tggzzz wrote: ↑Sat Feb 15, 2025 10:15 am
AVGresponding wrote: ↑Sat Feb 15, 2025 9:52 am Overall it's very clean inside, helped no doubt by a previous owner removing the NiCd's from the battery pack.
Mine was too, even though the NiCds had made their presence known.

For fun make sure you understand the function of Qx/Cx, x=1,2,3,4. It come from the era where people made decade counters from three transistors and a handful of passives.

Doing more with less is always the most fun.

Here are the final communications between myself and the seller:

AVG: "Hi,
Just to let you know I picked it up from the Post Office yesterday (I wasn't in when they tried to deliver it last Friday), and the packing did its job.
The mains lead is a bit sketchy, as expected, will get some nice new rubber insulated flex for that. The test leads are definitely for display purposes only xD
Powered it up and been playing with it today, glad to see someone removed the NiCd's, that would have been a pain to clean up!
Chasing a dry joint/dodgy socket (digit two), some good fun!
Left you top feedback, and thanks again. Last time I tried to buy one of these, the seller cancelled the sale as the price wasn't what he wanted.

best regards and good luck with your phd,
AVdG"

Seller: "Hi ! I'm so pleased the meter arrived ok and the packing done its job. I'm so pleased that its gone to a good home. The meter was restored by the person I bought it from, undoubetly the reason the NiCd. The price is no issue with knowing its gone to a good home. Thanks again for the postiive feedback - i had a few disappointments where I had to give refunds, so its always cheers me up when I get good news
Thanks again and cheers for the good luck - i've got tough supervisors, but its all in the name of research !"

Such a pleasure to deal with good folks on ebay, and such a contrast to the last time I tried to buy one of these.

Posted: **Sat Feb 15, 2025 1:43 pm**

AVGresponding wrote: ↑Sat Feb 15, 2025 1:21 pm Doing more with less is always the most fun.

Such a pleasure to deal with good folks on ebay, and such a contrast to the last time I tried to buy one of these.

Yes and yes.

Looks like you got it for a decent price; I sold mine for more than that at a hamfest.

Posted: **Sat Feb 15, 2025 4:56 pm**

Thanks for the 8120A upload to BAMA, though interestingly enough, the 8100A is closer...

The inverter and display driver in the 8125A are closer to the 8100A, on the board, though interestingly the schematic for the 8120A is closer, but the parts list shows lots of the components that are in the 8125A as "not used".

Posted: **Sat Feb 15, 2025 5:48 pm**

I never needed to look at the PSU, and was only interested in the DVM stuff

Posted: **Sat Feb 15, 2025 5:54 pm**

Did you figure out what the 800Ω 30W resistors are for? Are they a heater I wonder?

Posted: **Sat Feb 15, 2025 6:04 pm**

AVGresponding wrote: ↑Sat Feb 15, 2025 5:54 pm Did you figure out what the 800Ω 30W resistors are for? Are they a heater I wonder?

ISTR I did, but I forget

Clearly "follow the wires" and RTFSM is in order

Might they have been part of the battery charger?

Posted: **Sat Feb 15, 2025 9:50 pm**

AVGresponding wrote: ↑Sat Feb 15, 2025 4:56 pm Thanks for the 8120A upload to BAMA, though interestingly enough, the 8100A is closer...

The inverter and display driver in the 8125A are closer to the 8100A, on the board, though interestingly the schematic for the 8120A is closer, but the parts list shows lots of the components that are in the 8125A as "not used".

Any idea what tape machine that is?

Posted: **Sun Feb 16, 2025 8:30 am**

25 CPS wrote: ↑Sat Feb 15, 2025 9:50 pm
Any idea what tape machine that is?

An obsolete one!

My guess would be upper consumer level deck from Technics or perhaps Akai. If I never have to work with tape again, I am a happy person.

OTOH, my record player:

The Mono/Stereo button on the built-in RIAA preamp suffered from a dearth of working Midget Flange 14V lamps, that was fixed by ordering #382 lamps from Mouser.

Posted: **Sun Feb 16, 2025 11:25 am**

tggzzz wrote: ↑Sat Feb 15, 2025 6:04 pm
AVGresponding wrote: ↑Sat Feb 15, 2025 5:54 pm Did you figure out what the 800Ω 30W resistors are for? Are they a heater I wonder?
ISTR I did, but I forget Clearly "follow the wires" and RTFSM is in order

Might they have been part of the battery charger?

They aren't shown in any of the manuals I have seen so far (two versions of 8100, the 8120)

Posted: **Sun Feb 16, 2025 12:35 pm**

AVGresponding wrote: ↑Sun Feb 16, 2025 11:25 am
tggzzz wrote: ↑Sat Feb 15, 2025 6:04 pm
AVGresponding wrote: ↑Sat Feb 15, 2025 5:54 pm Did you figure out what the 800Ω 30W resistors are for? Are they a heater I wonder?
ISTR I did, but I forget Clearly "follow the wires" and RTFSM is in order

Might they have been part of the battery charger?
They aren't shown in any of the manuals I have seen so far (two versions of 8100, the 8120)

Hmmm.

All the same value, 800 ohms, possibly 20W.

Suspect two identical sections, the black wires and the white wires, each section in parallel.

If wired in series 2400ohms 60W => 120kV

if wired in series 266ohms 60W => 16kV

No help there.

Follow the wires.

Posted: **Mon Feb 17, 2025 4:08 am**

mansaxel wrote: ↑Sun Feb 16, 2025 8:30 am
25 CPS wrote: ↑Sat Feb 15, 2025 9:50 pm
Any idea what tape machine that is?
An obsolete one!

My guess would be upper consumer level deck from Technics or perhaps Akai. If I never have to work with tape again, I am a happy person.

OTOH, my record player:

The Mono/Stereo button on the built-in RIAA preamp suffered from a dearth of working Midget Flange 14V lamps, that was fixed by ordering #382 lamps from Mouser.

I remember that scene from Pup Fiction being used as a standalone music video for the Girl You'll Be A Woman Soon song and I did some digging and it's a Teac X2000.

Why the dislike for magnetic tape though? For me, it's Pro Tools and 16mm film because I'm fed up with taking on more and more work so the professional slackers can watch more Youtube.

Posted: **Tue Feb 18, 2025 6:10 am**

25 CPS wrote: ↑Mon Feb 17, 2025 4:08 am
I remember that scene from Pup Fiction being used as a standalone music video for the Girl You'll Be A Woman Soon song and I did some digging and it's a Teac X2000.

Why the dislike for magnetic tape though? For me, it's Pro Tools and 16mm film because I'm fed up with taking on more and more work so the professional slackers can watch more Youtube.

Where do I start?

Noise
Lacking treble
Dropouts
Rewinding
Having to bake old tapes
Degaussing
Alignment, and to what standard?
Oh, the alignment tape is broken
Worn out rubber roller
Wow and flutter
Phase misalignment between channels
Saturation
CCIR or NAB hubs
4-track 1/4" vs 2-track 1/4 and the resulting incompatibility
...

Making ones and zeroes of the sounds ASAP and then committing them to SSD and possibly spinning rust (while magnetic still, an evolved form good enough) is the only sensible way.

Test Equipment Anonymous

Fluke 8125A

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