Fluke 99 II - Taredown-Fault find and hopefully repair (now with photos)

[little_grey]

Hi all,

Inspired by the forum i picked up a fluke 99 which has problems powering up.
i attempted to turn it on, but alas, all is did was squeak at me.

so, its come apart. I have looked at the and found much the same.
obviously with more buttons.


so without further ado, here are some photos and there i think the fault is. but as to why, thats where your help comes in.

First up the unit itself. generally looking in good condition no major marks or scratches - rubber already removed


as with the fluke in the video by dave, it opens up like a beautiful electronic book with parts nicely laid out. (EDIT) just spotted the large caps hashed on the top of the scope probes


here is a close up of the screen and keyboard side. I am condident the keyboard is working as when powering up is attempted it does squeek as i said. going to leave that for now


This is the back of the board with the BNC and bannana connectors at the top. not looking too bad... at first glance


with it being a power issue i had a closer look at the DC input, nothing obviously at fault here


front side again and there is a small dent in the cap but nothing serious though the 'sheild' to the right does look like its gotten hot. ..... better look on the other side


ahh, well that'll be making soimething unhappy for sure. question is, has it blown the track out, and which componants has it taken with it. infact, which componant failed to start with.




so now i have an area to look at my plan is to have a look at the service manual and see if i can glean anything from it, but if you can save me time and throw some ideas arround i'd be very happy to hear them.


as a bit of background I generally work with cars so this tank of a thing is ideal, very little i work with is ideal for the task. checking crank signal patterns or ensuring the ECU is firing injectors as expected.
We have a Fluke 123 at work, but it doesnt have cursors (a right faff) and i have also got a  THS710a but still getting to grips with that.

[alm]

If we are supposed to see pictures, I do not see any except Dave's video. Probably a permission issue. Try opening the same thread in a private browsing window to see what other people see.

[little_grey]

you are right, not sure wh it would appear on mine but not anyone elses.
permissions were there.

i'll try again in my work break later

[little_grey]

If we are supposed to see pictures, I do not see any except Dave's video. Probably a permission issue. Try opening the same thread in a private browsing window to see what other people see.

cheers ALM, it was more of a HTML code issue than a permissions issue.
they should all be visible now.

[EHT]

You can start by finding the service manual: Google for Fluke_93-95-97_Service_Manual.pdf. It looks very similar to your pictures, not sure what the difference between the 99 and the others is.

Those burnt semiconductors look like diodes V2539, V2533 and FET V2542 which are in the power circuit (p221). I can't easily make sense of it with it spread over a few pages.

If i had to guess, this could have happened due to plugging in a PSU which has the polarity around the usual way (+ve centre) which is NOT how this one is wired, perhaps whilst having the batteries in.

Without looking at it properly I'd say:

• remove all the obviously burnt components
• check the PCB tracks and any other damage
• test the physically close semiconductors for shorts with a meter (also use diode test mode), plus have a look for others in the path of the burnt ones
• replace (all part numbers are in the manual)
• try with batteries before trying the PSU (make sure your lead is correct polarity and see my previous post on how to make a lead if rqd)

[little_grey]

I found the 97 service manual last night but didn't get to sharing.
With you on the power side of things as the layout looks the same.
To bolster that the power pack is the same for that range.

As for how it happened I couldn't be sure as I acquired it in this condition.

I'll dig out the numbers of the affected area and post them later today.

Thanks for the reply

[little_grey]

following up on EHTs post, the service manual for the fluke 97 is avaialble here (at time of writing)
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm93_95_97_fluke_93_95_97.pdf
it appears the section i am interested in is much the same as the manual. 9-16 to be exact.


related to the photos in the first post

and the coils on the other side.


I have noted some variation as on the 99 there is a single resistor at the bottom of the image where as the diagram suggests there should be 2.

oddly a poke with a multi-meter seems to suggest that the parts are working ok. so time to get some replacement parts in and see what happens

[little_grey]

well i replaced part v2633 today and no joy.

i am open to suggestions at this point.