TDS210/220/224 polarizer replacement: I found the correct way to do it! - Page 1
Forum section: electronics / testgear

author: EduardoLM
author_rank: Contributor
timestamp: June 02, 2025, 09:36:03 pm
content: I see many pictures on the web of TDS2xx scopes with a blue tinted, low contrast LCD. These had their polarizer films replaced by the incorrect type. The correct one is of FSTN kind, I found that only recently. This video shows the procedure, and how the correct polarizer reatores correct color tint and contrast! Video is in portuguese, but auto translated captions work quite well.https://youtu.be/VWjwBSqSBJ8

author: jpanhalt
author_rank: Super Contributor
timestamp: June 02, 2025, 09:51:43 pm
content: Thank you for positing here. I have a TDS210 that I still use occasionally when my much newer Rigol doesn't show what I need. Fortunately, last time I used it, I didn't have that problem.

author: EduardoLM
author_rank: Contributor
timestamp: June 02, 2025, 10:19:15 pm
content: I'm happy that I found how to give nem life to these old scopes. Polarizer rot is a common problem, and it's easy to fix by replacing them, but some LCDs are very picky on the polarizer type. And this one was hard to figure out! I hope this helps more people with the same problem!I also made a video showing the results of replacing old CCFL backlight with a led strip, it's on the same YouTube channel.

author: temperance
author_rank: Super Contributor
timestamp: June 02, 2025, 10:31:29 pm
content: QuoteI have one of those and I've never seen this problem. The LCD contrast is temperature dependent and the scope hardware/software does not automatically compensate for that. With a 5 °C difference, the display can be almost black with something visible around the edges.Maybe a stupid question but have you tried adjusting the contrast? The contrast adjust buttons are the the two lower context sensitive buttons next to the screen after you pressed the "Display" button.

author: EduardoLM
author_rank: Contributor
timestamp: June 02, 2025, 11:46:03 pm
content: Quote from: temperance on June 02, 2025, 10:31:29 pmI don't know about yours, but I mean this, see attachment (frame taken from a random YouTube video).Where screen should be black, it's blue. Sometimes, the white / light background goes to a light green tint. These are consequences of incorrect polarizers. In my research, I found out that later mono LCD screens, mainly dot matrix ones, need the FSTN polarizer type. Simpler / older LCD screens, like those on 7 segment calculators, don't need FSTN polarizer.And yes, I'm aware of contrast adjustment. It's also interesting how the scope has great picture at 50% when switched on. Then gets darker when warmed up. Then I need to decrease contrast to 30% to compensate. This may be related to the temperature / contrast relationship you mentioned.

author: TERRA Operative
author_rank: Super Contributor
timestamp: June 03, 2025, 05:40:18 am
content: Do you have a link to the polariser films you purchased?I have a few THS700 series scopes that have the same problem and would be repaired in the same way.

author: temperance
author_rank: Super Contributor
timestamp: June 03, 2025, 09:26:01 am
content: QuoteI see. My scope is about 25 years old and has the original polarizer and still works fine.

author: squadchannel
author_rank: Frequent Contributor
timestamp: June 03, 2025, 09:45:40 am
content: Quote from: TERRA Operative on June 03, 2025, 05:40:18 amThere was no link in the video, but perhaps thishttps://item.taobao.com/item.htm?_u=33s8grt6697ca&id=610116223737or thishttps://www.aliexpress.com/w/wholesale-fstn-polarizer-film.htmlI had been looking into polarizers for DSTN (Dual scan CSTN) lcd and knew that I need a retardation film, but it was difficult to get one.my surprise, it is now available. It seems that the demand for this film has increased since it is used in retro games such as Game Boy.I bought the one in the Taobao link immediately after watching the video. I will use it for my DSTN LCD.

author: EduardoLM
author_rank: Contributor
timestamp: June 03, 2025, 03:59:47 pm
content: Quote from: TERRA Operative on June 03, 2025, 05:40:18 amI bought mine from a dealer here in Brazil, it's not from an online store.. But I can check with him if he ships outside the country.Eduardo

author: EduardoLM
author_rank: Contributor
timestamp: June 08, 2025, 02:28:30 am
content: For those who didn't understand what I meant by "blue tint when using wrong polarizer", here's a video showing exactly what I meant:https://youtu.be/o5uE3ckNXE8