Seeking Fluke 27/FM Service Manual

[Dave Wise]

Does anyone have a Service Manual for the Fluke 27/FM DMM?  Not the Operators Manual part number 828558, I mean a real service manual with schematics.

Thanks,
Dave Wise

[Fungus]

Did you try google?

https://www.google.com/search?q=Fluke+27%252FFM+service+manual

[Gyro]

Did you try google?

https://www.google.com/search?q=Fluke+27%252FFM+service+manual

Not very helpful... Fluke 27 User and Service - of course. Fluke 27/FM User - yes. Fluke 27/FM Service - not that I've ever been able to find!  The FM is the [Edit: Mil?] true RMS one.

[Fungus]

You need to be very specific about the model, "27FM" doesn't mean much. The one in Dave's video is model "27FM".

Maybe that manual doesn't exist. I found some old threads here asking the same question, no reply.

Here's another clue:
https://www.eevblog.com/forum/testgear/fluke-27fm/msg589796/#msg589796

[bdunham7]

Fluke 27/FM Service - not that I've ever been able to find!  The FM is the [Edit: Mil?] true RMS one.

There is a "service manual"

https://radionerds.com/images/5/58/TM_11-6625-3199-14.PDF

But that still isn't very helpful and there is no schematic to be had within.  Unless you need to troubleshoot the AC converter part of the circuit, the regular 25/27 manual should do AFAIK.

[bdunham7]

You need to be very specific about the model, "27FM" doesn't mean much. The one in Dave's video is model "27FM".

Anyone have any idea what the heck /FM means in either context?  A/AF = Air Force, or perhaps Army/Air Force, /AN = Army/Navy (I think)  but /FM?

[Kean]

I suspect there was intentionally no detailed service manual published.

The Army operation manual (TM 11-6625-3199-14) for the AN/PSM-45A specifically states:

No general support troubleshooting is authorized or required. Upon failure, return the entire contents of the end item to unit level for disposal

There is the mentioned support maintenance & parts list (TM 11-6625-3199-24P-1) but it is of pretty limited value.

https://radionerds.com/index.php/AN~PSM-45 - note that the AN/PSM-45 is a different model DMM, only the AN/PSM-45A files apply to the 27/FM.

Maybe the /FM is "For Military".  Seems too obvious...

[Fungus]

Unless you need to troubleshoot the AC converter part of the circuit, the regular 25/27 manual should do AFAIK.

Yep. They should be very similar inside.

[AVGresponding]

I suspect there was intentionally no detailed service manual published.

The Army operation manual (TM 11-6625-3199-14) for the AN/PSM-45A specifically states:

No general support troubleshooting is authorized or required. Upon failure, return the entire contents of the end item to unit level for disposal

There is the mentioned support maintenance & parts list (TM 11-6625-3199-24P-1) but it is of pretty limited value.

https://radionerds.com/index.php/AN~PSM-45 - note that the AN/PSM-45 is a different model DMM, only the AN/PSM-45A files apply to the 27/FM.

Maybe the /FM is "For Military".  Seems too obvious...

Interesting, given that there are service manuals for the mil versions of the 87V and 18xII/28x meters, which are far more complex and modern

[Gyro]

Unless you need to troubleshoot the AC converter part of the circuit, the regular 25/27 manual should do AFAIK.

Yep. They should be very similar inside.

Side by side comparison... https://www.eevblog.com/forum/testgear/fluke-27-27fm-side-by-side-tear-down/  [Edit: Note, the 27 shown is the later single thermistor revision, the original was the same thermistor configuration as the /FM]

[Dave Wise]

Thank you all for your comments.  I guess I should have said that yes, prior to posting I read all Eevblog 27/FM posts, Fluke's 27/FM Operators Manual, and TM_11-6625-3199-14, and searched the web for '"Fluke" "27/FM" "service"' and '"Fluke" "27/FM" "schematic"'.

Regarding recommendations that I use the 27 manual, since 27______smeng0100.pdf is ten years newer than the 27/FM, mightn't the contemporaneous 8025B be closer?  (Instruction Manual, P/N 824482, 1988.)  Are there other sister models (TRMS and averaging) where both have schematics, so we can see how Fluke connects their RMS chip in a circuit that was designed to average?

Dave Wise

[bdunham7]

The manual that you should use for everything other than the AC converter section is https://assets.fluke.com/manuals/25_27___smeng0000.pdf right from the Fluke website.  It is scanned a bit oddly because it was published in a booklet format and you'll have to piece together the wiring diagrams but AFAIK it is all there.

There is no datasheet that I can find for the SC77174 TRMS chip so your idea of looking at other models using the same chip would be the logical next thing to try.  I haven't looked at various schematics of the earlier 80xxA/B models and I'm not familiar with them, but if you do find two that have the same main ASIC but one is averaging and one uses the SC77174 then that should be your guide.

[Dave Wise]

After a casual (half-hour) examination of the two manuals, 25_27___smeng0000.pdf P/N 738138 1984 and 8025B___imeng0100.pdf P/N 824482 1988, I believe the early 27 and the 8025B are identical except for the name.  Either manual is fine.  The 8025B manual has an error, the schematic omits the REL and MIN/MAX buttons as if it's a Fluke 25 instead of a 27.

Oh, and at https://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg391860/#msg391860, Robomeds says the same... in 2014.

At https://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg364468/#msg364468, Excavatoree says the 8026 is an 8020 plus SC77174 TRMS, so I will compare those manuals.  But they use an older measurement chip, the DIP-40 P/N 429100.  I don't think there is another instrument with TRMS that also uses the 27's measurement chip.  (P/N 700112.)

The SC77174 has different part numbers, 637801 in the 8026B, 605063 in the 8060A.  Any idea why?

[bdunham7]

The 8025B manual has an error, the schematic omits the REL and MIN/MAX buttons as if it's a Fluke 25 instead of a 27.

You're going to find all sorts of errata and revision discrepancies in these old instruments.  The schematic probably just didn't get updated from the 8025A.

I don't think there is another instrument with TRMS that also uses the 27's measurement chip.  (P/N 700112.)

Probably not, I had a look in some old catalogs and I don't see any candidates.  The 27 ASIC and design is quite different from the earlier 8020 and 8060 types.  8025A/B excepted of course.  And the TRMS circuit on the other models seems to reduce down to a single DC result that is sent to the main ADC.  The converter circuit is not connected in the involved way that the averaging circuit seems to be on the 27. 

The SC77174 has different part numbers, 637801 in the 8026B, 605063 in the 8060A.  Any idea why?

The 8026A part is listed as "select", the 8060A as "custom".  IDK what the means but multiple part numbers for similar things is a another quirk of these old manuals and instruments.  I don't think they had a second source for this.  It's a pretty arcane subject, the 8026A is pretty rare.