Fluke 87 IV missing a chip - Page 1
Forum section: electronics / repair

author: bluke
author_rank: Newbie
timestamp: September 02, 2023, 02:30:22 pm
content: Hey, I found an old dirty Fluke in the trash and it's missing a chip. From pictures I found in the forumi guess it should be a white chip labeled "CTX 01-13905" and the third line I think is a serial number or a specific config of this chip.Does anyone know what this chip does and where I can get one?

author: wasedadoc
author_rank: Super Contributor
timestamp: September 02, 2023, 03:03:35 pm
content: That is not an IC. It is a transformer. Part of the DC-DC power supply. The 1307 IC nearby ishttps://www.analog.com/media/en/technical-documentation/data-sheets/1307fa.pdfThe missing part is probably custom made for Fluke. I'd guess your one is missing because it was taken to fix another meter.

author: bluke
author_rank: Newbie
timestamp: September 02, 2023, 03:17:11 pm
content: Thanks for the quick reply! I had more luck searching for 187 instead of 87IV and found this post:https://www.eevblog.com/forum/testgear/fluke-187/msg536864/#msg536864"LT1307 DC-DC converter driving a transformer. It appears to generate three separate output rails based on the output diodes and caps. I think I read something saying that it can run the batteries down to above 1 volt each, which seems pretty good. The transformer is by Coiltronics, who appear now to be owned by Cooper Bussmann."Couldn't find the specific part online so you're probably right about it being customMaybe I'll try my luck with Fluke support.

author: donlisms
author_rank: Frequent Contributor
timestamp: September 02, 2023, 04:08:12 pm
content: Are you hoping this meter can easily be brought back to life by replacing this part, or are you thinking of it as a more challenging project? It seems unlikely that someone would pull a part from an otherwise working meter... and especially if it's value is then declared "zero!"

author: bluke
author_rank: Newbie
timestamp: September 02, 2023, 05:03:54 pm
content: I'm definitely up for a challenge, but if I can't get this transformer replaced, why even start?I'm measuring a few shorts across the capacitors/MOVs? in the attached image.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 02, 2023, 06:43:36 pm
content: Quote from: bluke on September 02, 2023, 05:03:54 pmNone of your red box outlines contain a MOV. That cylinder in the upper right corner is cell, battery or supercap, probably backup voltage for the clock.

author: bluke
author_rank: Newbie
timestamp: September 02, 2023, 07:13:53 pm
content: Yeah the big one is a 5.5V 0.1F Capacitor.Are the smaller ones burnt capacitors or are they supposed to be that color?

author: wasedadoc
author_rank: Super Contributor
timestamp: September 02, 2023, 07:24:14 pm
content: They are supposed to be that colour. Multi Layer Ceramic Caps can develop shorts caused by physical damage.

author: bluke
author_rank: Newbie
timestamp: September 03, 2023, 01:52:25 pm
content: I desoldered a few things and measured them on their own:the 3 small capacitors are all shorteda slightly longer capacitor from the other side of the board is also shorted4 diodes "33-16 J6 2" are OL with the diode test. There's another one that measures 0.7V so I think it's fineThe supercap is shorted in one direction (think I have to wait a very long time for the resistance to go up) and MOhms in the other direction so I think it's also fine.My guess is this Fluke took a good drop because the transformer pads look like it was ripped out.

author: Zoli
author_rank: Frequent Contributor
timestamp: September 04, 2023, 07:19:11 am
content: Quote from: bluke on September 03, 2023, 01:52:25 pmThose are ferrite beads; they suppose to be conductive. And the 33-16 "diodes" are in fact tantalum capacitors...

author: jchw4
author_rank: Regular Contributor
timestamp: September 11, 2023, 06:37:44 am
content: You need this transformer. I don't know where you would get one, but there is nothing you can do unless you have it.I posted some tracinghttps://www.eevblog.com/forum/repair/sick-fluke-89-iv-(fluke-189)/msg3574496/#msg3574496that might be useful in your analysis.