Where can I get a replacement A1242 transistor?

March 28, 2011 11:55 AM

Where can I get a replacement A1242 transistor?

I blew up a LumoPro 160 strobe a.k.a. speedlite, apparently by firing it too quickly. (Let's leave the notion of whether a strobe should blow up by using it too quickly on the table. Yes I bought a cheap-ass strobe and yes I'm regretting it.) Upon disassembly, I found two three-pin devices which have clearly let out all of their magic smoke.

I removed them from the board and they look like this: http://www.photi.ca/photos/1231749129_BLkj6-L.jpg

(Yep, I've ruined some of the traces, and that's okay, I can fix it later. The components were wired on the board in parallel.)

I searched DigiKey for the visible part number, A1242, and it seems to be a power transistor by Toshiba. Unfortunately, digikey doesn't stock them and will only order them in lots of 800. I don't want 800. I want two.

Assuming I've identified the right part (have I?), from whom can I get two (or maybe four) of them sent to me in Canada?

posted by seanmpuckett to technology (8 answers total)

I removed them from the board and they look like this: Link to photo of removed A1242 devices.
posted by seanmpuckett at 11:55 AM on March 28, 2011

Mouser electronics says they are end-of-lifed.

Mouser has the "show similar" button there. So depending on pinouts, specs and what not (I'm not an EE, my last soldering was 10 years ago), you may find a compatible part to use instead. (Get the datasheet for the 1242 first, then start comparing .. )
posted by k5.user at 12:04 PM on March 28, 2011

"Vintage" semiconductors sometimes show up on ebay. There's one of your 1242s in the UK right now - maybe check again in a few days.
posted by moonmilk at 12:20 PM on March 28, 2011

Yes you have the right part: the full part number is 2SA1242. I don't quickly see a suitable replacement due to the high VEBO of -8 (typical seems to be -5).
posted by fritley at 12:56 PM on March 28, 2011

It's not the most time effective way to search for this, but see if there's a ham radio flea market anywhere around you. Or ask a ham. My dad has buckets of different transistors, capacitors, & other electronics goodness in his garage.
posted by smirkette at 3:25 PM on March 28, 2011

According to octopart, Quest Components has some in stock.
posted by moonmilk at 3:48 PM on March 28, 2011

Don't.

Get the data sheet, analyze it, and get a replacement that has better specs. Unless you enjoy looking for sources for a part that is marginal in its application. Seek help from a EE friend or acquaintance.

I'm unfamiliar with this part and this application, and without a schematic or the actual board, not able to lend much to the search, but google turns up a lot of info and the data sheet on the part was easy enough to find. Doesn't look at that unusual... at least to me. NTE doesn't have a cross reference on the part, and while there appears to be a KA1242, I could find no sources for it, either. Have you checked eBay?

Also, unless you have a particular reason to stick with the package that this part comes in, you may find something closer to these specs in a slightly different package, such as a TO-220. That may help you find an alternative.

Is the thing you are repairing expensive/valuable/rare enough to warrant repair? If it's borderline and unreliable in design, it might just be a bad choice to fix it, as fixing it may become your new hobby.
posted by FauxScot at 3:50 AM on March 29, 2011

FauxScot: it's a $200 strobe; if I can fix it for an hour of effort and a few bucks in parts that's good value. If it keeps failing of course I'll just throw it out. I don't have the knowledge to substitute a better part; that's a much larger time investment.

fritley: thanks for the confirmation!

moonmilk: Thanks for the octopart link and the in-stock information from Quest; I almost bought from Quest until I was confronted by absurd shipping fees and an order minimum. Ultimately I bought two of them from the UK eBay seller; $13 from them was much better than the $70 from Quest.

Question resolved! Thanks, everyone.
posted by seanmpuckett at 6:17 AM on March 29, 2011