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Fluke 8125a Multimeter

Phones- Digital, Analogue, PABX, Receivers, transmitters & military equipment.
 
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Fluke 8125a Multimeter

Post by Lloyd » Fri Nov 16, 2012 9:48 pm

Hi :)
As promised, here's some pictures of the 8125a I bought off ebay earlier this week! It arrived today, very well packed.
It's in fairly battered condition, but internally it looks nice and clean (smells a bit funny though!)
I have fitted a plug and put some power into it, and it flickered a bit then settled with zero's on the Nixies. One thing I did notice is that I'm getting more than one digit lighting up in each tube, so when there's supposed to be a '1' on, I have '2' lit up as well, but at about half the brightness of the '1'. I don't know if this is just a feature of Nixie's though, as I've never seen any in use close up before. From what I could make out on the display, it was reading the voltage I tested it with very close to my newer Fluke meter!
A label on the case states it has the option for battery power too, there aren't any inside it, so does anyone know what voltage and where they connect to?
I need to repair the test leads that came with it, as the original wire has gone the way of rubber wiring in old radio's - rock hard!! I'm pleased it came with all it's leads too, and a sealed bag with some different probe ends.
Anyway, here's some pictures!

regards,
Lloyd.
Attachments
IMG_1764.jpg
IMG_1760.jpg
IMG_1763.jpg
IMG_1768.jpg
IMG_1770.jpg

 
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Re: Fluke 8125a Multimeter

Post by freya » Fri Nov 16, 2012 10:11 pm

Now thats built to last, the camera possibly make the tubes look brighter than they actually are.

Only things maybe to check are the smoothing caps, a scope on the supply rails will give the answer.

Nice one :thumbl:

stephen

 
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Re: Fluke 8125a Multimeter

Post by Refugee » Fri Nov 16, 2012 11:17 pm

I have a counter that i intend to use on a transformer winder.
It had a partly lit 1 all the time and it had taken a 7490 out with it.
I tested the tube with an HT power supply and a 100K resistor and it was faulty.

 
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Re: Fluke 8125a Multimeter

Post by Lloyd » Sat Nov 17, 2012 12:59 pm

Hi Stephen,
the camera does make them look a lot brighter than they are, although they are nice and bright in reality too. My iphone camera seems to be overexposing all photo's for some reason :|
It certainly does feel built to last, also easy to get into as there's just 6 screws and the whole lot pulls out of the case. I'll dig out a scope later and see what's happening on the supply.

Refugee, I'll possibly give the nixies a shot on a psu too, hopefully their not at fault, as the problem does seem to be across all of them!

I had a look at some video's of Nixies working on youtube last night, and they do seem a lot clearer than the ones in the fluke. I did consider putting a piece of darker filter material over the display to try and cancel out the dim glow, but I'd rather get it right!

Cheers,
Lloyd.

 
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Re: Fluke 8125a Multimeter

Post by Lloyd » Sun Nov 18, 2012 12:31 am

Ok, some progress :=D
I had the thing in bits today, mainly because I wanted to clean the front and buttons. I also took the Nixie's out and gave them a quick test on external power, and they all seem fine, all the digits light individually without any of the others lighting at the same time. I also pulled off the plastic parts of their sockets and gave them all a damn good scrub with IPA, and also cleaned the PCB with it around the sockets. This seems to have partially cured the problems with more than one digit lighting at a time, I had 1 and 2 appeared stuck together, 4 and 5, and 9 and 0. Now I'm left with 9 glowing dim in the background, no matter what number is supposed to be glowing. This is present in all 4 tubes all the time. I pulled the DM7441 from it's socket and powered up without it, and the 9's go out, I also scrubbed the IC socket and the IC itself, and even removed the socket from the board to make sure there were no shorts under it, then put it and the IC back and the fault remained. I compared voltages on the IC pins and found that each pin for each digit that wasn't lit was at about 45-50 volts, but pin 2 (connected to no.9 in the tube) was at about 15v when the digit wasn't supposed to be lit. I came to the conclusion the IC may be faulty, maybe it leaks a bit? I haven't got another to try in the socket, so I've left it for now.
I didn't get to scope the power supply lines either, as I couldn't get to my scope! I was having a tidy up before the Fluke arrived, and the only scope I could get to was a Hameg that doesn't work... :roll:

Regards,
Lloyd.

Oh, I also found a date stamp inside it - Jan 20 1977 :)
Attachments
IMG_1775.jpg
Just after cleaning the board - notice the '9' dimly lit
IMG_1784.jpg
All back together

 
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Re: Fluke 8125a Multimeter

Post by freya » Sun Nov 18, 2012 9:48 am

looking much better now, well done.

Stephen

 
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Re: Fluke 8125a Multimeter

Post by Lloyd » Sat Dec 01, 2012 8:24 pm

Just a quick update:
Managed to get 4 N7441 IC's off ebay to try in place of the DM7441, the results are promising, the permanently half-lit '9' in every tube is now gone :=D so the original chip seems to be at fault. the only remaining issue is that after the meter has been on for 15 mins or so I get other digits lighting faintly inside the tubes! it appears that if a digit is lit in one tube, it'll light in all 4 tubes, just very dimly. Similar to the first fault. I'm guessing there's a cap going leaky somewhere...
When I get my workshop revamp finished I'll get back to it, I'll dig the interweb for a manual of some sort too.

Regards,
Lloyd.

 
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Re: Fluke 8125a Multimeter

Post by freya » Sat Dec 01, 2012 8:43 pm

I know what the manual looks like, maybe he is contactable ?

http://www.epier.com/BiddingForm.asp?1817064

Also David Simpson on UKVRR had/has the same model so may be worth a PM ?

Stephen


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