tds 460 power supply problems - Page 1
Forum section: electronics / repair

author: ght_marius
author_rank: Contributor
timestamp: September 20, 2015, 01:01:38 pm
content: HiI recently bought this scope TDS 460 with a power supply faulty but can not find the schematic diagram. If anyone have the schematic diagram or any idea on how to fix this power supply.any help much appreciate it.thanks Marius

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 20, 2015, 03:12:03 pm
content: Probably bad capacitors.They didn't release any schematic level service information, it's only "replace board X".The supply doesn't look unusual so it should be easy to follow along with its operation.Have you checked if it powers up when disconnected from the main board? Shorted capacitors elsewhere is a possibility (the primary fault is SMT electrolytics leaking).Tim

author: Daxxin
author_rank: Regular Contributor
timestamp: September 20, 2015, 06:51:44 pm
content: Not sure but if its PS-1690 its almost the same of LeCroy model that cannot remember exactly what modeldifference is only output voltages , can find schematic of lecroy at ko4bb web site.

author: ght_marius
author_rank: Contributor
timestamp: October 08, 2015, 06:41:56 pm
content: HiLooks like it`s not the capacitors, no change in behaviour, and in the end the main transistor end up shorted and it took with it a few more components with it:1n4148MJF16006A1N5234BCUSTOM RECTIFIERand possible the teckronix custom chip 100004First I have managed to open the custom rectifier , and I have found a diode and possible a triac mac228a8 that`s faulty , maybe you can help me to identify the diode and the use of it. I also found this web site in Italian and he managed to remove the green compound of the custom chip 100004 of this web sitehttp://digilander.libero.it/chopin.i/varie/riparazioni.htmlI have managed to make a schematic of the custom rectifier but if you think it`s wrong I will try to do it again, some components the make and model got lost when I was removing the compound. The 1n4148 might be wrong and 1n4006 rectifier module.

author: ght_marius
author_rank: Contributor
timestamp: October 08, 2015, 06:56:23 pm
content: now the pictures

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 09, 2015, 02:01:11 am
content: You depotted a potted assembly?Tim

author: tec5c
author_rank: Frequent Contributor
timestamp: October 09, 2015, 02:03:42 am
content: Yeah that baby's broke!Is that really from a 460? If so, that thing must have been through hell.With reference to the pictures, I'm sure you have a strong idea about what needs replacing. Start with those then test surrounding components...

author: hegar93
author_rank: Newbie
timestamp: October 17, 2015, 11:08:18 pm
content: Hi,I got myself a TDS 420 with a faulty PSU some time ago and got it working again, here is the thread on the Tektronix Forum:http://www1.tek.com/forum/viewtopic.php?f=5&t=6283&st=0&sk=t&sd=a&hilit=tds+420&start=10Main problem was the optocoupler and the LM339 for overcurrent shutdown. Maybe you can get some usefull hints in there.The potted assembly seems to be a voltage doubler for 120V (and maybe a crowbar), but the one in my scope looked a bit funny, so disconnected it and it still works a treat.At least for 230V it is not needed for normal operation. "mikeohm" writes a bit more about that in the last posts...You can get the schematic of a very similar PSU in this manual for a LeCroy scope:http://www.ko4bb.com/manuals/index.php?dir=LeCroyGet the one for LeCroy_9354A-M-L and go to page 425/426 for the supply.hegar

author: ght_marius
author_rank: Contributor
timestamp: December 12, 2015, 11:38:41 am
content: HiThis is the custom chip 100004 picture and I have found a few components faulty like the transistor Q1,ZD3,U1,D4,Q4.Q4 I can not find the type and model , when I removed the green stuff I removed the type and model ass well , if anyone knows the components please share with me . I managed to do the schematic of the ceramic board with components in Altium Designer .Anyone who need the files please give a shout.thanks marius

author: ght_marius
author_rank: Contributor
timestamp: December 14, 2015, 07:51:59 pm
content: The capacitors of this custom chip are not all updated on the schematic diagram , only some of them, but when I get some free time I will do it.

author: scopeman
author_rank: Frequent Contributor
timestamp: March 31, 2016, 11:46:31 pm
content: Quote from: ght_marius on December 12, 2015, 11:38:41 amMarius,Do you have a PDF of that schematic you worked out for this module? The same part is used in LeCroy scopes and we are trying to nail down the schematic and parts.Thanks,SamW3OHM

author: maxxim
author_rank: Contributor
timestamp: January 11, 2020, 06:19:13 pm
content: Hi, what is the value of the tantalum capacitor on the underside PS-1690 power supply pcb (hybrid pin 13-19).Thanks

author: elbass7
author_rank: Newbie
timestamp: December 18, 2022, 12:10:36 am
content: I tried downloading the PrjPCB file to open it, but Altium says there's not document inside. Do you have the printed circuit board design for thei A1 100004 green potted custom board for the Tektronix TDS-420 power supply?Thanks,

author: max_programmer
author_rank: Newbie
timestamp: February 06, 2025, 07:54:15 pm
content: Hello!I’m also working on a replacement for the green hybrid in the TDS 400 series oscilloscopes, and your project would be really helpful. Could you share your Altium project, including the schematic files? I would greatly appreciate any help!Thank you!

author: CaptDon
author_rank: Super Contributor
timestamp: February 07, 2025, 04:04:07 am
content: I think the item you are calling a custom rectifier is actually the voltage control for 120 / 240 automatic voltage selection. Is it a module with three wires? Yellow, Orange and Blue if I remember correctly.

author: supramike
author_rank: Newbie
timestamp: March 25, 2025, 04:15:47 am
content: I've been scratching my head at this on that Auto ranging input voltage module. Looks like it's just a voltage doubler circuit if you input 120v. The part number is 51258901 hidden underneath the Power Systems stickerHere's the PSU mod from the LeCroyOwnersGroup It was a PDF which I couldn't see until I joined their group to see the files. This is their grouphttps://groups.io/g/LeCroyOwnersGroup[ Specified attachment is not available ]Thanks to the LeCroy group for this. Mods can we make the PSU Mod file a sticky since it seems to be a common problem?