Electronics > Repair

Fluke Scopemeter 95/97 AC adaptor and batteries


Hi. On my first post I'd like to share a tip with everyone.

I just got a secondhand Fluke Scopemeter (model 95) which didn't come with its rechargeable battery or AC power adaptor. I didn't think that would be a problem until I saw how much they both sell for, even copies. I managed to solve this, so here it is if you need to do the same.

The problem with the AC adaptor, is that Fluke have made a special one which is non-standard. It is very deeply recessed into the unit and the hole is very narrow. The first attempt i made to push a plug in there got stuck and i had to disassemble the unit to get it out! Also the original is a 15V DC source with the polarity unusually reversed to have the positive on the outside, ground centre. The meter can actually operate on a wide range of voltages, so 12V is fine as it is common. The meter can take alkaline or rechargeable batteries. It does this by means of a metal tab on the battery pack. Of course, these packs sell for double the price of just buying the equivalent cells..

Here's what you need:
- a standard 5mm x 2.1mm DC power plug like the type sold by Maplin in the UK
- any old 12V DC adaptor at least 400mA
- if you with to keep the existing jack on the adaptor, then a matching line socket.
- heatshrink and insulation tape
- 4 x 1.2v NiMH C-cell batteries

.. and here's what you need to do.
- unscrew the plastic cover from the 5mm plug and discard it
- take a metal file and file the metal rim of the plug down by about 0.5mm until you can push it into the recess. ONLY PUSH VERY GENTLY otherwise it will jam in there.
- solder a figure of 8 cable to the power plug using heatshrink to insulate the connection to the central pin, and then add a few layers of heatshrink over the whole thing to fashion a plug body. Best to have it exit at 90 degress, so make a bend in it. See pic.
- splice this onto your power adaptor or put the line socket on it. Remember the meter needs opposite to normal polarity.
- if you will always use rechargeable batteries, you can internally short the charging lead to the + of the battery, which is what the tab on the battery pack. You must remember and never insert alkalines if so otherwise these could explode.

The meter itself is great. You have to consider it like a super-powerful multimeter rather than a bench scope though. I also thought it useful for working on any live circuits such as SMPS, LCD monitors etc which you cannot connect a grounded scope to. Of course you could use isolation transformers or isolated probes but the scopemeter is a nice addition. Also note that the original probes are hugely expensive. You can buy insulated probes made by MC/Staubli for much less. These have plastic coated BNCs for working on live kit.



In case others want to put their lathe at work, here are the dimensions of the official plug:

It goes in up to the tapered bit.
Anything slimmer will also fit as long as the electrical connection is good.
(5x2.1 mm DC plug)

The PM8907/001 PSU is just a transformer, rectifier and capacitor.
Quite easy to make for less than the price of an official one.
All the complicated stuff is done by the PM97 and it will take any input between 8 and 20 volts.

Keep in mind that if you want to leave the PSU connected this may affect the meter's isolation.

I recently made a new plug up for mine.
I started with digikey Part No : 102-4786-ND

My original measures 6.25mm where the drawing indicates 6.1mm, so I chucked the plug up in the lathe and turned it down to 6.4mm. Perfect fit. I also tried one at 6.5mm and that was fine also.

I turned down a collar depth of 14.5mm from the tip.

The short one was the prototype. I went too deep and ate the internal thread.
There's *just* enough meat in the cover to make it work. I'll probably screw it together with a bit of epoxy for a "just in case", but it's all pretty firm.

Edit : Probably should have done this first, but the bore in my scope is actually 6.8mm. I might knock up another one with more meat on the bones!

Better than my bodge, but nonetheless mine is still working :)


--- Quote from: EHT on May 13, 2021, 10:50:54 pm ---Better than my bodge, but nonetheless mine is still working :)
--- End quote ---

It was your "bodge" that gave me the inspiration.


[0] Message Index

There was an error while thanking
Go to full version