Seeking Fluke 27/FM Service Manual - Page 1
Forum section: electronics / testgear

author: Dave Wise
author_rank: Regular Contributor
timestamp: April 11, 2025, 02:27:08 pm
content: 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

author: Fungus
author_rank: Super Contributor
timestamp: April 11, 2025, 04:32:01 pm
content: Did you try google?https://www.google.com/search?q=Fluke+27%252FFM+service+manual

author: Gyro
author_rank: Super Contributor
timestamp: April 11, 2025, 06:01:27 pm
content: Quote from: Fungus on April 11, 2025, 04:32:01 pmNot 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.

author: Fungus
author_rank: Super Contributor
timestamp: April 11, 2025, 06:39:15 pm
content: 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

author: bdunham7
author_rank: Super Contributor
timestamp: April 11, 2025, 06:40:30 pm
content: Quote from: Gyro on April 11, 2025, 06:01:27 pmThere is a "service manual"https://radionerds.com/images/5/58/TM_11-6625-3199-14.PDFBut 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.

author: bdunham7
author_rank: Super Contributor
timestamp: April 11, 2025, 06:43:57 pm
content: Quote from: Fungus on April 11, 2025, 06:39:15 pmAnyone 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?

author: Kean
author_rank: Unknown
timestamp: April 11, 2025, 07:10:16 pm
content: 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:QuoteThere 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...

author: Fungus
author_rank: Super Contributor
timestamp: April 11, 2025, 08:27:00 pm
content: Quote from: bdunham7 on April 11, 2025, 06:40:30 pmYep. They should be very similar inside.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 12, 2025, 09:52:20 am
content: Quote from: Kean on April 11, 2025, 07:10:16 pmInteresting, given that there are service manuals for the mil versions of the 87V and 18xII/28x meters, which are far more complex and modern

author: Gyro
author_rank: Super Contributor
timestamp: April 12, 2025, 10:05:33 am
content: Quote from: Fungus on April 11, 2025, 08:27:00 pmSide 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]

author: Dave Wise
author_rank: Regular Contributor
timestamp: April 12, 2025, 03:15:10 pm
content: 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

author: bdunham7
author_rank: Super Contributor
timestamp: April 12, 2025, 04:36:30 pm
content: The manual that you should use for everything other than the AC converter section ishttps://assets.fluke.com/manuals/25_27___smeng0000.pdfright 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.

author: Dave Wise
author_rank: Regular Contributor
timestamp: April 13, 2025, 02:52:50 am
content: 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 areidenticalexcept 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 athttps://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg391860/#msg391860, Robomeds says the same... in 2014.Athttps://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?

author: bdunham7
author_rank: Super Contributor
timestamp: April 13, 2025, 06:06:27 am
content: Quote from: Dave Wise on April 13, 2025, 02:52:50 amYou'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.QuoteProbably 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.QuoteThe 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.