[SOLVED] Fluke 8842A DMM - no display

[enut11]

My Fluke 8842A DMM  has a blank display. I checked all the supply voltages, replaced the electros, re-soldered the transformer PCB traces, checked for any burnt or overheated parts, all to no avail. Also checked the 4.5vAC and 5v DC bias to the display and all good. Finally got around to dismantling the front panel and I found what looks to me like a dead display with two 'smoke' traces at the top - see pic. In the process of dismantling the meter I managed to break the mains power switch
So, now looking for a replacement VFD and they seem to be very scarce. I also have a vague memory of someone who produced a custom LCD drop-in for the 8840/42 but could not find a lead on that one.
enut11

[TheDefpom]

Have you checked the driver IC's for data in/voltages out? (check on a scope for the pulses)

The drivers are U215, U217, U218 they also have a -30V rail just to drive the display, make sure that is present.

[J-R]

https://www.ebay.com/itm/155853129116
https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/

[enut11]

Have you checked the driver IC's for data in/voltages out? (check on a scope for the pulses)

The drivers are U215, U217, U218 they also have a -30V rail just to drive the display, make sure that is present.

The rail at the regulator output measures -5v with the display connected and -30v when I unplug the display.
This seems to indicate a dead VFD?

[floobydust]

To my eyes, the VFD display is dead - it's got air in it   The Getter in the two corners, once it turns white and flakes off inside, is a clear indicator. I would look for cracks or chips on the display that let air in. Healthy Getter is usually black or chrome.
If this is true (air in tube) the filaments will keep drawing higher than usual current and not glow orange.

[enut11]

https://www.ebay.com/itm/155853129116
https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/

Thanks everybody for your suggestions.
Just bought the Ukrainian LED module, currently the cheapest solution for my problem.

[enut11]

I received my display kit  from @AHOL. 3 weeks earlier than forecast!
The only problem was that we were about to go on holidays 
Back now and looking forward to getting my 8842 back in service.
enut11

PS
5 stars for customer service

[enut11]

Just finished installing @AHOL's LED display in my Fluke 8842A and it mostly went well. My experience notes in Reply #96 at

https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/new/#new