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Electronics => Repair => Topic started by: Denis1024 on November 08, 2019, 02:49:14 pm

Title: Scopemeter 97 poor contrast
Post by: Denis1024 on November 08, 2019, 02:49:14 pm
Hello,
I bought an old Fluke 97, but unfortunately it was down. I repaired it, one of the failures was the backlight. Now everything is fixed, but the LCD has a very poor contrast, at the limit, hard to read, even with a strong light or even with the backlight.

The pixels are not dark, but gray.
I wonder if such an LCD screen can be damaged for years?
Is there someone who owns a 97' with a good contrast?

I found this thread:
https://www.eevblog.com/forum/testgear/old-philips-fluke-97/100/ (https://www.eevblog.com/forum/testgear/old-philips-fluke-97/100/)

It seems that a polarizer can be damaged over the years?
Could someone confirm that?
Thanks
Denis
Title: Re: Scopemeter 97 poor contrast
Post by: rvalente on November 08, 2019, 04:25:27 pm
Ive had this trouble with my ths720p, bad polarizer, had to replace it. The contrast is not the same as the genuine material from sharp but, is very useable.

You should post a picture but, if the screen is inverting colors from the center to the edges in a circular form, its very probable the polarizer ia bad.

check https://www.eevblog.com/forum/repair/fluke-744-display/ (https://www.eevblog.com/forum/repair/fluke-744-display/)
Title: Re: Scopemeter 97 poor contrast
Post by: testpoint1 on November 12, 2019, 05:38:05 am
yes, very old, the plastic need to be replaced it.
Title: Re: Scopemeter 97 poor contrast
Post by: george.b on November 19, 2019, 12:13:33 pm
Like rvalente said, bad polarizer. Extremely common in 90s LCDs.

I reuse polarizers from broken, modern LCD screens for repairing those with some success. The color is usually a bit off, but meh :-//
Title: Re: Scopemeter 97 poor contrast
Post by: pocal on August 13, 2020, 10:16:24 pm
bonjour le mien est en panne je sais pas dans quel état est l’Écran, je cherche des infos sur l'alimentation,je n'ai pas de tension nulle part sauf sur le transfo ou j'ai 20 volt et le schéma de l'alimentation est mal détaillé , je trouve les éléments sur la sérigraphie, mais sur le schéma
avez vous un schéma de l'alimentation détaillé?  merci pour la réponse 
Title: Re: Scopemeter 97 poor contrast
Post by: rvalente on August 13, 2020, 11:37:53 pm
bonjour le mien est en panne je sais pas dans quel état est l’Écran, je cherche des infos sur l'alimentation,je n'ai pas de tension nulle part sauf sur le transfo ou j'ai 20 volt et le schéma de l'alimentation est mal détaillé , je trouve les éléments sur la sérigraphie, mais sur le schéma
avez vous un schéma de l'alimentation détaillé?  merci pour la réponse 

Altought I speak french, thats a english language forum.

Could you try better describing your troubleshooting?

https://www.cl.cam.ac.uk/manuals/pm93_95_97_fluke_93_95_97.pdf (https://www.cl.cam.ac.uk/manuals/pm93_95_97_fluke_93_95_97.pdf)
Title: Re: Scopemeter 97 poor contrast
Post by: shakalnokturn on August 14, 2020, 06:31:00 pm
Altought I speak french, thats a english language forum.

Could you try better describing your troubleshooting?

https://www.cl.cam.ac.uk/manuals/pm93_95_97_fluke_93_95_97.pdf (https://www.cl.cam.ac.uk/manuals/pm93_95_97_fluke_93_95_97.pdf)

Would be worth the bother trying englische even the French is very average.
Title: Re: Scopemeter 97 poor contrast
Post by: rvalente on August 14, 2020, 09:24:19 pm
Altought I speak french, thats a english language forum.

Could you try better describing your troubleshooting?

https://www.cl.cam.ac.uk/manuals/pm93_95_97_fluke_93_95_97.pdf (https://www.cl.cam.ac.uk/manuals/pm93_95_97_fluke_93_95_97.pdf)

Would be worth the bother trying englische even the French is very average.

Nice, how is your portuguese? Probably better than mine...
Title: Re: Scopemeter 97 poor contrast
Post by: shakalnokturn on August 14, 2020, 09:59:21 pm
No chance... I can hardly make any difference between Spanish and Portuguese.
I do find the Brazilian easier on the ear than the Portuguese though.