Fluke 75 & Fluke 73 Multimeter Spare Parts

[Degsy1962]

Firstly, apologies in advance if I have placed this in the wrong category or it has been answered before.
I have Two multimeters which have different faults but unable to find any details on repairs/answers which help. Firstly the Fluke 75 is showing 2 ohm when the lead posts are connected together. Board has been cleaned with IPA and have set calibration pot using a 3v reference on the DC volts scale. The soldered joints to the posts have been resoldered as a matter of ruling out any problems. Is this a case of a £30 calibration will fix? If so I am happy to do this.
The second meter, a Fluke 73 series 2 may be a simple fix if I can locate a supplier of spare parts. The rotary wafer switch has crumbled away and requires a new one soldering in. Unfortunately I cannot locate any suppliers other than a well known auction site offering spares or repair units for £50 upwards. Any information would be much appreciated as Fluke are not answering any Emails.

[retiredcaps]

Firstly, apologies in advance if I have placed this in the wrong category or it has been answered before.

Hitting the enter key would help us read your wall of text.

Is this a case of a £30 calibration will fix?

Calibration will not fix this.  As far as I remember, without looking at the service manual, there is no way to adjust the ohms reading.

Some suggestions.

1. Is DCV accurate?
2. Is ohms read accurate? 100 ohm? 1k? 10k? 100k?
3. Have you tried multiple IPA cleanings?  Sometimes it takes more than one IPA clean.
4. Can you post clear focused pictures of your pcb board?

Unfortunately I cannot locate any suppliers other than a well known auction site offering spares or repair units for £50 upwards.

You can try to buy a broken/as is Fluke and use it as a parts donor.  Or ask in the Buy/Sell section here.

[retiredcaps]

Ultrasonic bath helped Fluke 187 with 2 ohm offset with probes shorted.  See below

https://www.eevblog.com/forum/testgear/fluke-187-reads-2-ohms-high/

[Degsy1962]

Thanks for very quick reply.
I can confirm that the DCV readings are same as recently calibrated Fluke and an aging Beckman.
At present I can only check with resistor to hand of 100 ohm, this is reading 107.8 whilst calibrated meter is reading 99.8
I have access to ultrasonic bath but do I need to remove LCD display or any other parts. I have already soaked by spraying IPA all over board but is there any particular places to concentrate on?
Will post pictures if ultrasonic bath is unsuccessful.

Thanks again.

[retiredcaps]

I have access to ultrasonic bath but do I need to remove LCD display or any other parts.

Remove everything from PCB including LCD display, fuse and battery.  Just the bare pcb board for the ultrasonic bath.

[Degsy1962]

Will attempt to find bath in my well cluttered garage and post results and pictures if unsuccessful. From the amount of views am I correct in thinking that obtaining new parts is a bit of a non starter and that Fluke will keep all their parts for in house repairs?

[retiredcaps]

Fluke is highly unlikely to have any new parts for meters this old.  These meters are probably 25+ years old.

Your best bet is to be patient and look on ebay or try your local hamfests, craigslist/kijiji, etc for a cheap $5 to $10 USD unit to get a rotary switch.

[mzacharias]

Regarding the 75: Any chance the leads are actually 2 ohms or so?

Anyway, one could remove the 9v battery, engage the function switch to Ohms, and use another meter to measure the circuit resistance through the input jacks looking back into the circuit. I'm not sure what you'll get - I use this technique troubleshooting analog VOM's with Ohms problems, after removing the battery and shorting the battery terminals together. In any case, you might be able to compare the results to those obtained measuring another unit.

By the way - there  are schematics available on the older Fluke's.

[Degsy1962]

I have tried various leads and also temp soldering a link from com to V/ohm lead positions to no avail. Measuring back with battery removed is something not thought of. As stated earlier, this is a 25 year old meter so I suppose components "go bad". They do seem to be used by a lot of people and hold their prices well.

[retiredcaps]

Components can possibly drift over time, but since you have to take the Fluke 70 series completely apart to change battery and fuses, there is a chance contaminants are on the pcb.

[Degsy1962]

Yes, I suppose in that respect I am my own worse enemy. After having a meter written off due to a cheap battery I try and replace every 6 months or so even if the meter is reporting the battery as ok. The meter with the faulty rotary switch was dropped into a bath of a solvent called "blanket wash" and apart from the switch and clouding of the Perspex lcd cover, still works when manually set to desired function, a testament to their commercial robustness.

[SingedFingers]

You'd be surprised what an old Fluke can go through. Here's one I fixed: https://www.eevblog.com/forum/repair/fluke-8024b-won't-zero/

Service manual is here: http://assets.fluke.com/manuals/77______smeng0100.pdf

Section 3-10 has troubleshooting steps which will identify what needs testing. On the above it suggests one of the following problems if ohms isn't reading:

1. R1 shorted
2. E1 shorted
3. S1 bad
4. Q1,Q2 shorted
5. Loose pins on U1, U2
6. U1 bad

Worth checking those in situ with another meter.

TBH the things I'd expect myself with this as it's a relatively low range are the main switch contacts needing thorough cleaning or R1 (the big fusable resistor) being a short or Q1/Q2 bad as they will introduce an error into the measurement. If it's reading DC volts, from which everything else is derived, it is likely external to U1 analogue processor which is good news

[retiredcaps]

1. R1 shorted

You made a typo while posting.  It should read "R1 open".  R1 is the fusible resistor.

If R1 were open, you would get symptoms like in modemhead's blog entry below.

http://mrmodemhead.com/blog/fluke-87-fusible-resistor/

[Degsy1962]

Thanks for all suggestions, at present the pcb is on its second session in a ultrasonic bath. After the first treatment and 24hr air drying the resistance was worse with leads shorted, up to 75 ohm. Have now used soft tooth brush on rear of board and between pins on U1 and U2. I will check thru items suggested on troubleshooting chart when removed from bath and dried out.

[retiredcaps]

After the first treatment and 24hr air drying the resistance was worse with leads shorted, up to 75 ohm. Have now used soft tooth brush on rear of board and between pins on U1 and U2.

Sometimes moisture gets underneath U1 and U2 so it will affect the readings.  Scrubbing U1 and U2 is a good idea.  Modemhead uses a dental pick to drag between each pin.

If air drying doesn't help, use a computer fan/blow dryer to blow air for a couple of hours.  Although I have not tried it, some suggest putting the pcb into a toaster over at low temperature to help speed up the drying process.  Usually, air drying overnight works for me, but it all depends on your environment.

[Degsy1962]

FIXED!! My dilemma is at which point I was able to read 0.2 ohm leads joined together. Either way it was thanks to the most helpful advice from the people who suggested various solutions. So as to help anyone else, after the last soak and dry, (hair dryer on warm as suggested) also scraped out between pins on U1 and U2 using cocktail sticks (no toothpicks avail) also suggested, I put meter back together and set to ohms and achieved the magical 0.2 ohms. Thank you to all concerned.

[retiredcaps]

Glad you got it fixed.

Just remember that a Fluke 70 series I, II and III meter can run 2,000 hours on a 9V battery.  Yes, it is a good idea to take it apart annually to check for alkaline leakage, but you shouldn't have to change out the battery unless you use the meter 24x7.

Some suggest that a lithium 9V is less likely to leak, but I don't use lithium as I find them too expensive.

Nothing, today, comes even close to 2,000 hour runtime in a handheld multimeter.

[Degsy1962]

Good advice, as you said maybe I would be best to periodically check and not be over zealous (paranoid) as I fear I have done more harm than good.