Diode replacement for tv - Page 1
Forum section: electronics / repair

author: Tapped
author_rank: Newbie
timestamp: June 07, 2016, 01:23:46 am
content: I am in the process of repairing a tv's power supply. I have found all the parts needed except for a single diode. It is a black diode with a single brown band on the cathode end. The only other markings on it are T2D 90 (the 0 has a line under it). It is about 4mmx3mm. In the photos the markings look red, but in person they are more of a brown. After awhile of searching, i have only seen it mentioned in a few foreign forums.It is a Toshiba tv, and the model number of the power supply is: FSP236-4F01 (PK101v1510I). The diode in question is marked D501 on the pcb. Any information on this diode would be greatly appreciated. I'm wanting to order a replacement diode from mouser.Pictures of diode:https://imgur.com/a/FtTIJ

author: wraper
author_rank: Unknown
timestamp: June 07, 2016, 01:34:20 am
content: Show a photo where it is used. Should be easy to find a suitable replacement if it is known in which part of the circuit it is used.

author: Tapped
author_rank: Newbie
timestamp: June 07, 2016, 06:02:08 pm
content: https://imgur.com/a/chrVh#1: SR560#2: SR560#3: T2D 90#4: TZ15BI guess the tv died during a power surge, so you can see some burn marks around 1,2 and 3. Number 4 was giving me weird readings, so i'm just going to replace it. I'm going to replace all the electrolytic caps, and the fuse. I'm hoping nothing else was fried.

author: wraper
author_rank: Unknown
timestamp: June 07, 2016, 06:24:03 pm
content: That PCB discoloration is because those parts run hot for prolonged time, not because they are faulty. All of those diode failing at the same time is nearly impossible. That diode is part of the snubber. Must be about 800V ultra fast recovery diode, something with few amps max current would be safe. You should check nearby IC model and find a datasheet. Typical circuit will give you a clue what you can use instead. If those diodes measure fine, just leave them as is. Your fault likely is somewhere else. If standby psu is not running (part with tiny transformer), then you should check it first, probably small capacitors are faulty (if it just does not work and fuse wasn't blown).

author: Tapped
author_rank: Newbie
timestamp: June 07, 2016, 06:43:43 pm
content: I have tested all the diodes, and 1 and 2 were reading ~.144v. 3 was OL in both directions. Number 4 seems to be ok. For some reason when i first tested them i thought it was bad.edit: The tv would power on and off pretty fast and then eventually stay off.

author: BMack
author_rank: Regular Contributor
timestamp: June 07, 2016, 09:05:04 pm
content: I'd wager that U501 is bad as well, you may want to verify before you hit the checkout button on the diode.

author: wraper
author_rank: Unknown
timestamp: June 07, 2016, 10:03:39 pm
content: Quote from: Tapped on June 07, 2016, 06:43:43 pm0.144v is fine, those are schottky diodes. Number 3 then is bidirectional TVS diode, like this onehttp://www.shindengen.co.jp/product/semi/datasheet/U180_ST02D-82.pdfCompletely normal to measure open. Such diodes very rarely fail open, almost always become short.

author: wraper
author_rank: Unknown
timestamp: June 07, 2016, 10:18:31 pm
content: Quote from: Tapped on June 07, 2016, 06:43:43 pmNothing to do with diodes or faulty semiconductors at all. Most likely some faulty electrolytic capacitor. try to change C105 and if it does not help C504, C509 too.

author: Tapped
author_rank: Newbie
timestamp: June 08, 2016, 03:01:03 am
content: Quote from: wraper on June 07, 2016, 10:18:31 pmJust an update. I soldered the diodes back on, and just for the hell of it, i checked to see if it would power on the tv. When i hit the power button, the tv turned on and off for a few seconds and then stayed on. It would stay off before. Could this be caused from the circuit being completely drained?The plan is to change C105, C201, C202, C203, C205, C206, C207, C209, C210, C216, C504 and C509 to Nichicon caps. Which are all of the electrolytic capacitors except for the big 220v ones. You dont think i need to change U501? On the chip it says A6069H SK902 17HP.

author: BMack
author_rank: Regular Contributor
timestamp: June 08, 2016, 04:47:02 am
content: Wait, now it turns itself on and off then stays on? That changes everything. Change all the caps except the 560uf caps(You can but those are rarely the cause of failure), then see where we're at.If the u501 IC is bad it will normally be dead with no power indication or dead with power indication. You'll normally see low(or no) voltage or fluctuating voltage on the 5v line. I see those a lot on those types of power supplies so when I read that you found some diodes, that's what I recommend checking...but that's not the case if it's turning on now.Also, you may want to check the positive side of the bridge rectifier, it might just be the lighting but it looks like a crack in the solder.

author: wraper
author_rank: Unknown
timestamp: June 08, 2016, 07:44:11 am
content: I don't think you need to change all caps right away. Big 560uf caps are Panasonic. Cannot see what are others from the picture but don't look like CrapXons or any others which fail often. Vent style where can be seen suggests they could be Nippon Chemi-Con. Don't forget you will need LOW ESR capacitors for secondary side (C2xx capacitors). And better not just any LOW ESR but with ripple current rating not worse that original have, therefore you need to check their datasheets first before buying the replacements. If any ICs in the PSU were faulty, it won't work at all. As I said before try to change those small caps first, if secondary side caps are faulty, fault symptoms usually are different, it won't restart itself in that case.EDIT: found a bit better picture, according to vent style secondary side caps look like mix of Nippon Chemi-Con and Rubycon. Don't touch them before replacing those small capacitors.

author: Tapped
author_rank: Newbie
timestamp: June 08, 2016, 07:30:15 pm
content: I'm just going to order all of the caps. I looked through all the datasheets and it seems like the ones i have picked out are all within spec of the original ones. All of the caps are either Rubycon or Chemi-Con.Chemi-Con(KY) datasheet:http://www.chemi-con.com/upload/files/5/1/74811667552d6c4d41a84c.pdfRubycon(YXF) datasheet:http://www.rubycon.co.jp/en/catalog/e_pdfs/aluminum/e_YXF.pdfRubycon(YXG) datasheet:http://www.rubycon.co.jp/en/catalog/e_pdfs/aluminum/e_YXG.pdfC504: Rubycon YXF 22µF 50V 5x11mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1H220MDD/?qs=%252b6W0IEfz7IbTRlQaMYzqyw%3d%3dC509: Rubycon YXF 22µF 50V 5x11mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1H220MDD/?qs=%252b6W0IEfz7IbTRlQaMYzqyw%3d%3dC105: Chemi-Con KY 10µF 50V 5x11mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UPW1H100MDD1TD/?qs=sGAEpiMZZMtZ1n0r9vR22RH2kZvTh%252b0aRz87LrikrME%3dC216: Rubycon YXF 4.7µF 50V 5x11mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UPS1H4R7MDD1TD/?qs=sGAEpiMZZMtZ1n0r9vR22YeHFy5ijTdkUtyw62Kr0fE%3dC210: Chemi-Con KY 100µF 25V 6.3x11mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1E101MED/?qs=sGAEpiMZZMtZ1n0r9vR22YPz1L%252b%2fWYbmGyyo4Rf3ucM%3dC206: Chemi-Con KY 100µF 25V 6.3x11mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1E101MED/?qs=sGAEpiMZZMtZ1n0r9vR22YPz1L%252b%2fWYbmGyyo4Rf3ucM%3dC201: Chemi-Con KY 1000µF 35V 12.5x25mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1V102MHD/?qs=NRDD%252b9pa26HYzAmhrEUhsg%3d%3dC202: Chemi-Con KY 1000µF 35V 12.5x25mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1V102MHD/?qs=NRDD%252b9pa26HYzAmhrEUhsg%3d%3dC203: Chemi-Con KY 1000µF 35V 12.5x25mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1V102MHD/?qs=NRDD%252b9pa26HYzAmhrEUhsg%3d%3dC205: Chemi-Con KY 1000µF 25V 12.5x20mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1E102MHD6/?qs=M3AF6W7FHoCwzqBWfdUHvA%3d%3dC207: Rubycon YXG 470µF 35V 10x20mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UHE1V471MPD/?qs=sGAEpiMZZMtZ1n0r9vR22VnKtxyD4xsRm9O2vK82ebU%3dC209: Rubycon YXG 2200µF 10V 12.5x20mm replacement:http://www.mouser.com/ProductDetail/Nichicon/UPA1A222MHD6/?qs=sGAEpiMZZMtZ1n0r9vR22eNCVsT%252bBbilLkyD0AqRiyU%3dC209 is the only one i'm worried about. The original cap has a ripple current of 1900mA, but the replacement is 1890mA. There is a cap with a ripple current of 2360mA, but the impedance isn't within spec.picture with caps labeled:

author: wraper
author_rank: Unknown
timestamp: June 08, 2016, 10:38:21 pm
content: ESR spec is not so important in this case, 1890 mA is fine too. I bet all of those caps on secondary side are completely fine. Those series almost never fail. On the other hand, those small caps on primary side sometimes fail even if made by good manufacturer. The thing is, even if you check the datasheet for the same series, bigger capacitors usually have longer life time spec than smaller ones.

author: BMack
author_rank: Regular Contributor
timestamp: June 09, 2016, 05:22:02 am
content: C216 is a likely culprit or future culprit, any cap by a heat sink sees excess heat and wears faster than normal.As Wraper said, the specs for the C209 are fine.

author: wraper
author_rank: Unknown
timestamp: June 09, 2016, 08:44:56 am
content: Quote from: BMack on June 09, 2016, 05:22:02 amC504 and C509 most likely run hotter than C209