(Solved thanks to Roland) tds210 have problem with BL section - Page 1
Forum section: electronics / repair

author: nic77
author_rank: Contributor
timestamp: January 19, 2022, 02:07:40 pm
content: Good day to all ,an wish everyone well,i have a problem with my tds 210 , the back light is very dimm , so i opened and changed the ccfl neon ,nothing doing,still the same , as i searched web i could not find anything ,they say there is very high voltage on the output of the transformer , about a 1000 vac so i cant test that ,I checked the transformer secondary output for continuity and got 121 ohms , can someone help me with this issue as i never have worked with high voltage things, i am only a hobbiest and almost on pension ,would be very pleased , greetings to all nic77 from Italy.

author: RolandK
author_rank: Regular Contributor
timestamp: April 28, 2022, 05:39:12 am
content: On my Tektronix TDS 220 the ccfl was dark. One of the two transistors in the HV Converter was open collector. After replacing it worked, but there was only a very weak backlight.So i recycled the LED strip of a dead computer monitor from the dump. I looked for one with a frame with less than 1 cm or 1/2" deep . Someone had already opened the monitor, so i only had to dismount the display. The 23" display had at the bottom a LED strip with 4 rows each with 13 LEDs in series.From the length i needed 9 leds and just cut them off with some scissors for metall.Checked voltage and polarity with a 30V Power supply and 10kOhm in series.Soldered the recycled wires from the CCFL to the LED.Glued the LED strip to the display with hot melt glue.Disconnected the HV Converter for the CCFL and cut the board-connection to the ccfl connectorthe leds need about 23,7 V. The power supply has at the connector to the main board 27,8 V. So i mounted a 1kohm in series at the ccfl connector to get 4mAI soldered a twisted pair beween the connectors which i routed the same way as the ccfl supply to have some distance from the SMPSOn the way I marked the polarity on the LED, the wire and the boardNow my Scope has a nice LED illumination with about 4mA supply current and 1/4 W. Illumintion is a little more cool white than original.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 28, 2022, 07:00:14 am
content: Just in case you don't have it, here's a link to the service manual:https://download.tek.com/manual/071049203.pdfNot much help there, though. No schematics.

author: austfox
author_rank: Regular Contributor
timestamp: April 28, 2022, 11:32:19 am
content: I repaired the backlight for my TDS 210 last month. I had no illumination at all. Turned out it was the 2 Mosfets (from memory IRF3205s) driving the transformer.Edit: Sorry, looks like they are C3205 transistors. I took mine from another unit (TDS 220) that has other issues.

author: RolandK
author_rank: Regular Contributor
timestamp: April 30, 2022, 09:36:42 am
content: Now with pictures of the TDS 220 Power supply board:Connections for the LED with 1kOhmCCFL Converter disconnectedPiece of LED strip

author: nic77
author_rank: Contributor
timestamp: July 01, 2022, 11:49:47 am
content: Thank you all very much for you help , yes i have seen many fixes but very well explained by Roland a great very well explained ,thank you Roland for your time , thank you austfox for foto of the transformer with measurements ,as one friend just gave me a 220 in bad shape so i measured the transformer and dont get the resistance in the foto so i will do the led modification as i do have a piece of led strip ,thank you all once again ,nik.