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ajgriff 2nd Dec 2019 12:27 pm

Fluke 77 Series II Repair Using Donor
5 Attachment(s)
It’s now around thirty years since these meters were in production and it’s often necessary to find a donor if repairs are needed to a cherished example as parts are now in short supply. However, it is not always appreciated that there were some significant design changes towards the end of the production run and that some parts are not readily interchangeable between the two versions. The attached photos show some of the differences. The earlier version is on the left with the later type on the right in each photo.

Photo 1 - On the earlier version the yellow button symbol under the legend ‘PRESS’ is a solid colour whereas on the later example it’s a yellow outline. This represents a simple way to distinguish between the two versions.

Photo 2 - The lugs for the lower fixing screws on the upper half of each case are of a different design.

Photo 3 - The later version has an additional lower case moulding (arrowed) that protrudes through slots in the circuit board. Also, the pillars through which the case screws pass are taller and on the circuit board the components themselves are in different positions or have disappeared altogether.

Photo 4 - The ‘FLUKE 77 SERIES II MULTIMETER’ legend and the analogue numbering are printed on the LCD mask of the late version and the mask is blank on the earlier one.

Photo 5 - The ‘FLUKE 77 SERIES II MULTIMETER’ legend and the analogue numbering is printed on the inside face of the LCD window on the earlier version and the window is completely clear on the later one.

Some consequences and considerations regarding these design changes are highlighted below for the benefit of anyone wishing to swap parts from one version to another:

1. Fluke documentation refers to the circuit board and the attached LCD unit as the ‘PCA’ (Printed Circuit Assembly). An early PCA can’t be fitted to a later lower case because of the additional case moulding (Photo 1). However, a later PCA will fit an earlier lower case.

2. An early upper case can’t be mated to a later lower case because of the changes to the design of the case screw mounting lugs (Photos 2 & 3). In fact if this swap is attempted and the screws are tightened the upper case will break just below the LCD window. However, a late upper case can be fitted to an earlier lower case.

3. If a case half and/or a PCA can be interchanged (as above) it becomes necessary to swap the LCD window or mask in order to avoid a rather disconcerting shadow effect with the legends or their complete absence (Photos 4 & 5). It is better to swap windows rather than masks because the masks crack easily when being removed. Alternatively, the whole LCD assembly can be swapped (4 screws) allowing the contacts to be cleaned at the same time.

4. It is possible to carefully reduce the height of the lug pillars of a late lower case with a small file in order to make an earlier upper case fit. Similarly, and with great care, it should be possible to break out the additional moulding from a late lower case in order to fit an earlier PCA. The latter isn’t something I’ve tried due to the risk of causing peripheral damage to the case.

5. It should be noted that any case swapping, with or without modifications, will have some effect on Fluke’s original efforts to meet safety standards applicable at the time of manufacture. It is a matter of judgement as to whether or not this has significant implications in terms of using the meter being repaired.

6. I can’t comment on the interchangeability of individual components between the different PCAs as I’ve never found any definitive documentation covering the later type. The downloadable manuals I’ve come across on the Fluke website and elsewhere are unhelpful in this regard. As far as a serial number change point is concerned the best guess I can offer is somewhere around 68000000 based upon the relatively few meters I’ve seen.

7. If a donor meter is required it may be best, in the first instance at least, to try and find a suitable candidate of the same type as the meter needing repair.

Finally, if anyone is contemplating trying to find a replacement upper case because of the commonly occurring fault of sheared switch end stops it’s actually quite straightforward to a carry out a satisfactory repair. Simply remove the range control knob, drill a small hole where the end stop used to be and replace the stop with a small piece of hard plastic super-glued in place. When the control knob itself is re-positioned and the meter is re-assembled the repair is invisible.

I hope that some of this is helpful to anyone contemplating the acquisition of a Fluke 77 Series II meter as a donor, either now or at some point in the future. If not, it was fun compiling this write up anyway. :)

Corrections, general comments or additional information would be most welcome. I don’t know for example whether or not the same issues apply to other meters in the Series II range (75, 73, 70, 23 or 21).


SiriusHardware 2nd Dec 2019 1:55 pm

Re: Fluke 77 Series II Repair Using Donor
Alan, thanks, this write up is especially timely for me as I have just such a project ongoing. It was a good idea to put the information in a forum thread.

SiriusHardware 3rd Dec 2019 12:30 am

Re: Fluke 77 Series II Repair Using Donor
5 Attachment(s)
Some details about my 'patient'.

After reading Alan's info above my first thought was that someone must have put mismatched upper and lower casings on this unit because the damage to it is more or less identical to what Alan says will happen if someone does that - however it looks to me as though both the lower casing and upper casing are both 'early version'.

I should stress that no meter of mine would ever be allowed to get into this state - it was damaged by another department where I work and was about to be discarded - I'd like to send it to the person whose meter it was for many years before he retired, but ideally not in this sorry condition.

ajgriff 3rd Dec 2019 1:03 am

Re: Fluke 77 Series II Repair Using Donor
Definitely an early version meter although I'd guess that some joker tried to fit the top half of the case to a later version, realised their mistake and reunited the (now) broken case with its original partner. The damage to the upper case screw lugs tends to confirm this theory. The battery box also has a chunk missing, not that it matters much since the top half of the case is scrap anyway of course. I notice too that the LCD support frame is broken which usually happens when someone tries to dismantle things by levering with a screwdriver (not a good idea). Incidentally, the low current fuse is the wrong type.


SiriusHardware 3rd Dec 2019 1:20 am

Re: Fluke 77 Series II Repair Using Donor
Thanks for the info about the fuse - I don't have another one with an original fuse to compare it with.

I can only imagine someone trying to lever the top half open if the upper case screws were originally hidden by bungs or something, but that would make little sense since you have to take the case apart at some point to replace the battery.

The display frame certainly has taken a beating at the sides, but luckily everything still works. I would not be looking to replace that since it will be out of sight if the casing can be repaired, hence my request (in wanteds) for a no-hope or blown-up but cosmetically OK 77 series II. I'd better now go and add that it's an early version I'm looking for as well.

ajgriff 3rd Dec 2019 1:47 am

Re: Fluke 77 Series II Repair Using Donor
I imagine the levering would only have come in to play when someone decided to try swapping LCD assemblies to solve the legend mismatch issue. The elastomeric strip contacts tend to stick over time making the assembly tricky to release even after the fixing screws have been removed. I guess this would have been before they broke the case. A tale of woe all in all.

The fuse should be an HBC/HRC ceramic type (630mA 250V fast).


SiriusHardware 3rd Dec 2019 1:54 am

Re: Fluke 77 Series II Repair Using Donor
Since the meter does actually work, I'm trying to imagine what issue it was they were trying to resolve by removing the casing and putting it on the wrong type of chassis before putting it back, broken, on the original chassis.

It has a rubber boot (grey) on it by the way, so it's hard to imagine it could have suffered drop damage, those protective rubber shrouds work pretty well in my experience.

I'll just have to be patient until the right one comes up. Thanks for the info about the correct fuse, do you know off hand whether they are available from mainstream sources like RS / Farnell?

ajgriff 3rd Dec 2019 10:21 am

Re: Fluke 77 Series II Repair Using Donor
It's a shame Fluke meters can't talk. I suppose we'll never know what fate befell this poor meter.

With regard to fuses, anything associated with the Fluke brand sold by mainstream suppliers tends to carry a price premium so I last bought some from here:

I'll have another rummage through the spares box to see if I can come up with anything suitable to help with the repair and will check for spare fuses at the same time. I'll send a PM if I have any success.


defender 4th Dec 2019 10:50 pm

Re: Fluke 77 Series II Repair Using Donor
Can new parts still be bought from Fluke?
I bought a new front and window for mine a while ago.

SiriusHardware 4th Dec 2019 11:00 pm

Re: Fluke 77 Series II Repair Using Donor
You know, I never actually considered that. I have a Fluke 'Scopemeter' in my loft which has the common fault of the adhesive display ribbon cable no longer sticking to the display. (Otherwise the instrument is OK, it just has a lot of black lines running across the monochrome LCD display).

I contacted Fluke a few years ago now when it still wasn't really very old and was told that spares were no longer available for it, so I had assumed that the same would apply to this 30-year old multimeter design.

SiriusHardware 5th Dec 2019 12:40 am

Re: Fluke 77 Series II Repair Using Donor
Well, I've fired off an email to them so we'll see what they say (I'll report any feedback from them here).

SiriusHardware 5th Dec 2019 11:07 am

Re: Fluke 77 Series II Repair Using Donor
I got a response to my query, very rapid, but rather cool, see below.

I've had this experience before with Fluke where they tell me the necessary parts are unavailable and then in the next sentence either invite me to send the item to Fluke for repair (when the part is obsolete, how would they do that?) or, as in the case below, to quote me (For what, when the parts are unavailable?)

The link just takes me back to the page where I found their contact details originally.

I emailed them again to query this and they clarified that the part is not available to purchase, and that I should contact the fluke service people, who originally sent me somewhere else, to see about the possibility of a repair by Fluke.

I have a feeling that if I send it to Fluke they will charge me for looking at it, and then tell me what I already know - that the necessary parts are no longer available. For the time being, I'm going wait for a 'spares or repair' specimen to come up.



Good Morning
Thank you for your enquiry.
This is now an obsolete part.
As you do not hold an active account with Fluke UK, we are unable to provide you with a quotation.
Please use the link to find details of your local wholesalers:

ronbryan 5th Dec 2019 11:33 am

Re: Fluke 77 Series II Repair Using Donor
It is just remotely possible that Fluke service department keep parts from scrapped DVMs.

For example Roberts Radio offered me a repair of a faulty DAB module on a Stream 202 (WM202), but because the module was obsolete, they would only quote for repair using a second-hand module. They would not sell the used module separately.


SiriusHardware 5th Dec 2019 12:14 pm

Re: Fluke 77 Series II Repair Using Donor
Well, in my original email to

I explained that I would be happy with cosmetically average but otherwise intact parts from a scrapped example, but they sent me straight through to another department which doesn't sell the parts new any more. I suppose they thought (reasonably) that in the first instance I would prefer new parts.

I'll go back to service on the above email and ask them specifically about the scenario you suggest, but if there is a minimum repair charge I think the time charged for would be well in excess of the two minutes it would take to swap a different casing onto it - granted, they would want to fully test it as well.

ajgriff 5th Dec 2019 1:33 pm

Re: Fluke 77 Series II Repair Using Donor
All sounds very typical of Fluke's policy towards parts and repairs. However, I'm intrigued by the fact that 'defender' managed to buy parts and would also be interested to know the costs involved? Also, did the parts come from a Fluke approved source or a third party?


defender 6th Dec 2019 12:08 am

Re: Fluke 77 Series II Repair Using Donor

Originally Posted by ajgriff (Post 1196920)
All sounds very typical of Fluke's policy towards parts and repairs. However, I'm intrigued by the fact that 'defender' managed to buy parts and would also be interested to know the costs involved? Also, did the parts come from a Fluke approved source or a third party?


It was a while ago but, it was Fluke, perhaps they changed their policy since then maybe a health and safety thing where they are scared of getting sued.
I think I still have the old bits somewhere, It was rather used I seem to think it cost 25 to 30 for the parts.

SiriusHardware 6th Dec 2019 12:12 am

Re: Fluke 77 Series II Repair Using Donor
I think if the meter had been a relatively recent or current model they could have been quite helpful with respect to parts supply - the reply wasn't 'No, we don't supply parts', it was 'No, we can't supply that obsolete part' which was not unexpected given the age of the design. I have contacted Fluke service again to see what they might have in the way of second hand / scrap casing parts, even if they insist on fitting them.

defender 6th Dec 2019 12:30 am

Re: Fluke 77 Series II Repair Using Donor
I found the front and the bag it came in but not the window the part number leads to this

ajgriff 6th Dec 2019 1:09 am

Re: Fluke 77 Series II Repair Using Donor
Interesting and many thanks to 'defender' for digging out the information. I might be wrong but I don't think that Galco is an official Fluke Service Centre and is therefore a third party supplier. As such Galco won't be obliged to comply with Fluke's long standing policies on supplying parts or undertaking repairs. The challenge might be the shipping costs as US rates have risen alarmingly in the last few years. Probably more cost effective to buy a used meter from a UK source.


SiriusHardware 6th Dec 2019 1:31 am

Re: Fluke 77 Series II Repair Using Donor
Arggh, what a shame as that's a 'late version' upper casing, not the 'early version' I would need. I'd also need the display window (with logo) as well.

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