Fluke 87 IV missing a chip

[bluke]

Hey, I found an old dirty Fluke in the trash and it's missing a chip. From pictures I found in the forum

i 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?

[wasedadoc]

That is not an IC.  It is a transformer.  Part of the DC-DC power supply.  The 1307 IC nearby is https://www.analog.com/media/en/technical-documentation/data-sheets/1307fa.pdf

The missing part is probably custom made for Fluke.  I'd guess your one is missing because it was taken to fix another meter.

[bluke]

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 custom

Maybe I'll try my luck with Fluke support.

[donlisms]

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!"

[bluke]

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.

[wasedadoc]

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.

None 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.

[bluke]

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?

[wasedadoc]

They are supposed to be that colour. Multi Layer Ceramic Caps can develop shorts caused by physical damage.

[bluke]

I desoldered a few things and measured them on their own:
the 3 small capacitors are all shorted
a slightly longer capacitor from the other side of the board is also shorted
4 diodes "33-16 J6 2" are OL with the diode test. There's  another one that measures 0.7V so I think it's fine
The 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.

[Zoli]

I desoldered a few things and measured them on their own:
the 3 small capacitors are all shorted
...

Those are ferrite beads; they suppose to be conductive. And the 33-16 "diodes" are in fact tantalum capacitors...

[jchw4]

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 tracing https://www.eevblog.com/forum/repair/sick-fluke-89-iv-(fluke-189)/msg3574496/#msg3574496 that might be useful in your analysis.