Fluke 27 AN Manual Needed - Page 1
Forum section: electronics / testgear

author: radiotek
author_rank: Contributor
timestamp: December 14, 2024, 09:56:59 pm
content: Fluke 27 AN Manual NeededI found the Fluke 27 FM but why is it so difficult to find the manual for the Fluke 27 AN ?Any help would be appreciated.Frank

author: daisizhou
author_rank: Super Contributor
timestamp: December 15, 2024, 03:05:04 am
content: They are 80% the same, the only difference is the TRMS conversion part.27/FM has a dedicated conversion chip

author: pinpassion
author_rank: Contributor
timestamp: April 04, 2025, 08:37:05 pm
content: Hi gang,I just picked up a Fluke 27/FM on Ebay sold as parts or repair. Of course, I want to repair it.I found a component on the board that is cracked straight through. In the manual for the 27 it is listed as RT1. I think it is associated with the input protection circuitry. It is located just above the MOV's on the main board. There are two of them, the other being located on the opposite side of the board. In the manual, the description of the part is:Thermistor, Rect., POS., 1K, +/- 40%, 25c Manufacturers Part # 911P84E102YU13 On the part it is labeled:TDK 8049I searched Digikey and got no hit. The other one on the board looks perfect. The rest of the board looks like new.Can anyone suggest a decent substitute? I am attaching two pictures. One is the cracked component, the other one is the second undamaged part.Any help is appreciated.Mike

author: AVGresponding
author_rank: Super Contributor
timestamp: April 05, 2025, 08:44:36 am
content: I don't think that's a thermistor, I think it's R2, which is a 3.5k 5% 5W wirewound

author: BU508A
author_rank: Super Contributor
timestamp: April 05, 2025, 08:53:30 am
content: Quote from: AVGresponding on April 05, 2025, 08:44:36 amCongratulations to your 5k posting.SCNR

author: Gyro
author_rank: Super Contributor
timestamp: April 05, 2025, 09:06:04 am
content: Quote from: AVGresponding on April 05, 2025, 08:44:36 amNo, it is a PTC thermistor. The high wattage resistors (R1 and R2) are down by the V/jack connection pad.R2 is actually a fusible metal film, not a WW - correct in the parts list, wrong on the schematic.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 05, 2025, 04:46:19 pm
content: Curiosity got the better of me so I took apart my turn of the millenium vintage 27-AN. It has a much simpler arrangement

author: Gyro
author_rank: Super Contributor
timestamp: April 05, 2025, 05:50:11 pm
content: Yes, the AN is different (and simpler).

author: daisizhou
author_rank: Super Contributor
timestamp: April 06, 2025, 02:05:45 am
content: They are different, the difference is the average value and the effective value (AC voltage)

author: AVGresponding
author_rank: Super Contributor
timestamp: April 06, 2025, 09:56:35 am
content: Quote from: daisizhou on April 06, 2025, 02:05:45 amYes but that should have no effect on the protection circuitry. I suspect the reason is they found fewer/cheaper parts would do the job just as well.

author: Dave Wise
author_rank: Regular Contributor
timestamp: April 10, 2025, 12:31:17 am
content: Upper right corner of your 27-AN photo, isn't the disc-shaped part to the left of the 3.5K WW resistor a PTC thermistor?Dave Wise

author: bdunham7
author_rank: Super Contributor
timestamp: April 10, 2025, 01:26:11 am
content: The Fluke 27/AN is a much newer model than the others (mine is from 2006) and the only one with a CAT III rating. It replaces the old design using a 1k fusible resistor R2 as overload protection and a 220k regular resistor R1 for the second input circuit (voltage sense for ohms, etc) The new design replaces these with a surge resistor plus PTC for input overload protection and the high-voltage 1M ceramic resistor for the secondary voltage input. The surge resistor is 3.5k, other later models used a 1k version. The YS4020 PTC and the 1M ceramic HV resistor (p/n 103454) are both used to this day in current models. With the more robust YS4020 earlier in the circuit, the PTCs further in were unnecessary.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2025, 03:42:58 am
content: Quote from: bdunham7 on April 10, 2025, 01:26:11 amI thought the newest one was the yellow/grey one as shown in Dave's video:It has CAT rating, etc.

author: bdunham7
author_rank: Super Contributor
timestamp: April 10, 2025, 03:55:02 am
content: You're right, some of them were labeled other than 27/AN on the back and IIRC that 27/FM version was confusing because people thought it was TRMS. The model number is actually still just "27" and there might be labels other than AN or FM applied to CAT III meters but I haven't seen them. The /AN was a military contract version. My 27/AN has the grey face with the yellow body so I don't think you can go by that.So lets just go with "CAT III Model 27"

author: daisizhou
author_rank: Super Contributor
timestamp: April 10, 2025, 04:00:49 am
content: Quote from: bdunham7 on April 10, 2025, 03:55:02 amNO.27/FM is a TRMS multimeter.Because there is an RMS chip inside.The others may be average values.

author: bdunham7
author_rank: Super Contributor
timestamp: April 10, 2025, 04:04:55 am
content: Quote from: daisizhou on April 10, 2025, 04:00:49 amIf it says 27/FM on the front it has TRMS. These meters were never made with CAT ratings AFAIK and had the old input circuitry.If it says 27 on the front and there is a sticker on the back that says 27/FM, as in the video just above, then it does not have TRMS. Again, AFAIK, these were all CAT III/1000V and had the new input circutry.

author: boggis the cat
author_rank: Regular Contributor
timestamp: April 10, 2025, 06:07:33 am
content: Quote from: radiotek on December 14, 2024, 09:56:59 pmI think this is the correct manual.

author: daisizhou
author_rank: Super Contributor
timestamp: April 10, 2025, 06:36:47 am
content: Quote from: boggis the cat on April 10, 2025, 06:07:33 amIt doesn't look like 27/FM，Because there is no TRMS chip

author: bdunham7
author_rank: Super Contributor
timestamp: April 10, 2025, 02:05:14 pm
content: Quote from: boggis the cat on April 10, 2025, 06:07:33 amThat version contains the parts list from the old models which doesn't match the schematics.Here is the revised version with the correct parts list.PN 690206November 1998 Rev.1, 9/03Fluke-27-service-manual.pdf(3854.21 kB - downloaded 26 times.)