Fluke 77

[Raptornet]

Hi guys

I have a much loved fluke 77, I've not used it for a while. Took it out my toolbox today and it's not reading AC. When i plug it in to a wall socket it will not give me a reading, the little bar graph at the bottom is flicks about.

Anyone know it it's repairable?

[ian_rodger]

Service manuals are available online from Fluke. Is it only the a.c. volts range that is not working? If so I'd start by checking C1 and R2 (based on series III diagram).

[ajgriff]

It probably is repairable. The most likely cause is dirty/oxidised switch contacts after a long of period without use.

Alan

[Raptornet]

Idk if this means anything, but having watched a couple of Fluke 77 YouTube videos. I've noticed when set to either AC or DC it will not settle on a zero reading, it will float around with a value between 200-400.

I did take the unit apart and spray switch cleaner over the main rotary selector switch, but didn't make much difference.

It's also probably worth mentioning, when I initially removed it from my tool box, it was dead. When I opened it up, I discovered the 9v had gone bad, outer labelled was stained, battery had apparently leaked. I couldn't see any PCB damage, used a cotton bud and some white vinegar to neutralize any acid on the contacts etc. Not ruling out that could be a factor. But I'd read online that there are one or two resistors in the 77 that if bad, can cause bad AC / DC readings. Servicing a multi meter is a little outside my wheel house.

[ldreossi]

More than likely the 9volt battery needs to be replaced. Its accessible after you undo the four Phillips-head screws at the back.

[Raptornet]

Yes, I replaced it with a rechargeable 9v. Wondering if that's what's causing my issues. ATM the only other meter I have is my AVO 12C. I have a variable PSU which I set to 9v.

On the AVO it's just a little over 9v, on the Fluke it's more like 12v

[murphyv310]

I'd try a non rechargeable battery even just to eliminate that from the list to check. Some devices don't like rechargeable batteries.

[SiriusHardware]

I've owned / used several Flukes and they were all able to operate well down to about 7.5V from the battery, although by that time the battery low symbol ought to be lighting up.

The OP didn't quite state whether any / all other ranges are working - reading it one way, the OP went to measure some AC voltage and found that it wouldn't, therefore ACV must be faulty. But how many of the other ranges are or are not working, has that been checked out? Knowing what works and what doesn't would narrow the field a lot.

Start out by using the continuity range to check the meter's own leads and probe sockets?

[Raptornet]

Hey guys

So I thought i'd get back to you. I went out to the Range and bought one of the delightful £8.99 Saber Multimeters, just so I could get a digital reading of the things I'm using to test the Fluke on.

So I have a variable DC power supply which can output max of 12v, it's a built old in the tooth but when set to 12v outputs 11.93v. Least according to the Saber when checked it just now. The Fluke is another matter, when hooked up it gives me a reading of 23.xx volts and the value slowly decreasing the longer I hold the probes to the barrel jack.

Continuity check, if I cross the probes it'll beep and show -.026
When i switch it to VAC the first thing is shows is .039 and then starts counting down slowly
Set to VDC and it's , 172
So something must be up, as it should read zero if nothing is connected to the probes.

Is there anyone on the forum who services meters? As I would REALLY like to get this working again, it was a gift from my late father-in-law, not to mention it's become my main meter for doing all my small electrical projects.

[Outrun_uk]

I'm the repair engineer at a calibration lab. If you get stuck PM me and will work something out.

Kev

[Raptornet]

Originally Posted by Outrun_uk

I'm the repair engineer at a calibration lab. If you get stuck PM me and will work something out.

Kev

PM sent, thank Kev!

[Outrun_uk]

Received the meter earlier and happy to say it’s now repaired, here’s some pictures connected to a calibrator and one of the failed component.

Kev

[Raptornet]

Blooming eck! That was quick! Honestly, I can't express enough thanks. Yeah it's just a meter, but also sentimental value which is priceless. Thank you

[Station X]

Spark gap. I had the same problem with my Fluke.

[ex 2 Base]

I also have Fluke 77, works OK on all ranges, but the sounder does work any more, had for many years and to me was expensive, any advice on fixing it will be much appreciated. Ted

[ajgriff]

Have a read through this thread:

https://www.vintage-radio.net/forum/...d.php?t=199252

Alan

[ex 2 Base]

Many thanks Alan and other members, I've read the article and kept a copy for future use.
As I lifted away the PCB I noticed a thin aluminium foil piece which I think was originally attached to the common terminal and the foil screening in the lower part of the meter case, Please tell me if I've got it wrong.
Unfortunately the two lower screw posts were really misaligned / damage, it made it difficult to get the PCB out. I haven't any IPA but thought Meth will be much the same, so will use that. I have located the beeper connections, one is really dirty. I'll later post the rate of progress.Ted

[ex 2 Base]

Back again, all reassemble and is now working, the sounder is quite loud pleased to say, as I have two hearing aids. Ted

[Diabolical Artificer]

Nice one Ted. Flukes are pretty repairable compared to DMM's by Tenma for instance.

Andy.