How to pick repair parts similar to the original? - Page 1
Forum section: electronics / repair

author: Mint.
author_rank: Frequent Contributor
timestamp: August 26, 2012, 05:35:36 am
content: So I am in the process of repairing an amplifier as you may have seen by my previous post. I think I have located the problem, but now I don't know where to find the TLP421 Photocoupler. What am I supposed to look out for when finding replacement parts?Datasheet:http://www.datasheetcatalog.org/datasheet/toshiba/2230.pdf

author: Rerouter
author_rank: Super Contributor
timestamp: August 26, 2012, 05:43:21 am
content: it would help to know if its being used as an analog signal transfer or a digital one, and how its being driven, either current or voltage,if analog you will want to find one with a similar current trasnfer rate and a similar IC vs IF charachteristic,if digital you only need to find one with the same or better on/off times and forward voltage

author: Mint.
author_rank: Frequent Contributor
timestamp: August 26, 2012, 07:05:01 am
content: Quote from: Rerouter on August 26, 2012, 05:43:21 amWell I'm assuming that it works as an analog signal transfer since it just turns on when mains voltage is on from what I can see.I've attached the schematic.

author: amyk
author_rank: Super Contributor
timestamp: August 26, 2012, 09:24:03 am
content: http://www.ebay.com/itm/5x-TLP421-P421-Triac-Driver-IC-Optoisolator-Photocoupler-Optocoupler-DIP-4-/110790266679http://www.ebay.com/itm/5-PCS-TLP421-DIP-4-P421-PHOTOCOUPLER-GaAs-IRED-/110929121524

author: Mint.
author_rank: Frequent Contributor
timestamp: August 26, 2012, 10:11:05 am
content: Quote from: amyk on August 26, 2012, 09:24:03 amToo expensive! I only need one!

author: SeanB
author_rank: Super Contributor
timestamp: August 26, 2012, 10:42:13 am
content: Go hunt down almost any dead SMPS, there will be one inside it that will fit the location and will do the job. Only needs to provide isolation, and only works at a low frequency, with only providing a mains present signal to the micro so that it can do an orderly shutdown and power on reset.

author: amyk
author_rank: Super Contributor
timestamp: August 27, 2012, 09:30:48 am
content: Quote from: SeanB on August 26, 2012, 10:42:13 amNewer ATX PSUs will have 2 or 3, older ones used transformers for feedback and didn't have any.

author: SeanB
author_rank: Super Contributor
timestamp: August 27, 2012, 03:40:07 pm
content: Pretty much any power supply that you find as a brick or a light mass wall wart will have one inside. Exceptions are the ultra cheap OHL ones, and some that use a tightly wound transformer with good enough regulation so that primary side regulation is good enough, a lot of the good low power cell chargers are doing that to save power in standby. Anything using a TL431 or similar on the secondary has one.

author: Mint.
author_rank: Frequent Contributor
timestamp: August 29, 2012, 07:29:10 am
content: Thanks everybody. Can't be bothered fixing this 6 or 7 year old thing anymore.

author: Mint.
author_rank: Frequent Contributor
timestamp: August 29, 2012, 11:20:27 pm
content: Quote from: jim_griff on August 29, 2012, 01:30:17 pmDelivery prices are crazy!