How to pick repair parts similar to the original?

[Mint.]

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

[Rerouter]

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

[Mint.]

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

Well 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.

[amyk]

http://www.ebay.com/itm/5x-TLP421-P421-Triac-Driver-IC-Optoisolator-Photocoupler-Optocoupler-DIP-4-/110790266679
http://www.ebay.com/itm/5-PCS-TLP421-DIP-4-P421-PHOTOCOUPLER-GaAs-IRED-/110929121524

[Mint.]

http://www.ebay.com/itm/5x-TLP421-P421-Triac-Driver-IC-Optoisolator-Photocoupler-Optocoupler-DIP-4-/110790266679
http://www.ebay.com/itm/5-PCS-TLP421-DIP-4-P421-PHOTOCOUPLER-GaAs-IRED-/110929121524

Too expensive! I only need one!

[SeanB]

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.

[amyk]

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.

Newer ATX PSUs will have 2 or 3, older ones used transformers for feedback and didn't have any.

[SeanB]

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.

[Mint.]

Thanks everybody. Can't be bothered fixing this 6 or 7 year old thing anymore.

[Mint.]

Thanks everybody. Can't be bothered fixing this 6 or 7 year old thing anymore.

Just in case you change your mind, I found the Element 14 store for Australia.

Here's the piece you want, although they'll probably charge a handling fee and possibly delivery cost on top. Perhaps the eBay link will work out to be cheaper.
http://au.element14.com/toshiba/tlp421-gb/optocoupler-transistor-o-p/dp/1225855

Delivery prices are crazy!