needed: 2SA1302

[nick78]

I need a single Toshiba 2SA1302 to repair an amp that I have...

I have read about the problems with counterfit/fake components and was wondering if there is a known reliable/safe source for these parts? I don't mind paying a premium in price to be sure it's the right part.., and I'm thinking I might buy two or three, in order to cut one open to verify it's the right stuff.

I know there are "better" replacements, but I don't want to replace the entire output section or modify the overall design. I just want to replace the blown part.

as an aside; what would cause a 2SA1302 to short across all pins? The device measures as a dead short from any pin to any pin. The amp worked the last time it was used and was fine when turned off. The next time it turned on it simply blew the fuse immediately.

any info is helpful.

thanks!!

 

[Centauri]

Toshiba haven't been making these since 1999, so ALL of the ones you can buy now are fakes (been caught badly by this recently).

However ONsemi make MJL1302, as replacement. Reliable ONsemi distributors such as Farnell will have good ones.

Do you know history of amp? - could possibly already have fake transistors. Try splitting the dud one to have a look.

Cheers

 

[nick78]

i know the amp has had two previous owners - both deny that it's ever been repaired, and based on the way it came apart, I don't think it's ever been opened up before.

i've tried splitting open the dead '1302 but so far it hasn't split. I whacked it good with the handle of a screwdriver on the side of the transistor about 50 times but only succeeded in creating a slight chip around the "ear".

attached is a pic of it with the slight damage from my attempts to break it open

I went ahead and ordered a couple 2sa1302's from digikey (and a couple of 2sa1943 as well); when i searched the forum a few people mentioned that digikey buys straight from toshiba and they should not have fakes (thus they should have NOS)...well, i ordered a couple and when I get them, will attempt to split one open and see. will post pics. if the 1302's are good I'll use them, if not then i'll use the 1943's, and if THOSE are fake..i guess i'll go with onsemi MJL1302. I wanted to keep the transistor as close as possible to original to avoid any unintended affects on the amp..

 

[sam9]

In the US, www.digikey.com and www.arrow.com still stock these. They are big distributors who get their stock either from Toshiba, still have stock on hand from Toshiba or have other reliable sources. At least I was told that when I asked.

This is repeating what you already know.

Your other option is to replace ALL the NPN/PNP pairs with 2SA1043 and 2SC5200. These are almost identicle to the originals - I think it unlikely that substituting these would change the sound of the amp in any discernable way.

 

[Centauri]

i've tried splitting open the dead '1302 but so far it hasn't split. I whacked it good with the handle of a screwdriver on the side of the transistor about 50 times but only succeeded in creating a slight chip around the "ear".

A sharp wood chisel will split them easily.

Cheers

 

[nick78]

Looks like a real one. ruler is mm, the 'chip' is about 5mm per side.

 

[Centauri]

Yep, that looks like original. All the fakes seem to have the chip covered in a white silicon stuff.

Cheers

 

[K-amps]

i know the amp has had two previous owners - both deny that it's ever been repaired, and based on the way it came apart, I don't think it's ever been opened up before.

i've tried splitting open the dead '1302 but so far it hasn't split. I whacked it good with the handle of a screwdriver on the side of the transistor about 50 times but only succeeded in creating a slight chip around the "ear".

attached is a pic of it with the slight damage from my attempts to break it open

I went ahead and ordered a couple 2sa1302's from digikey (and a couple of 2sa1943 as well); when i searched the forum a few people mentioned that digikey buys straight from toshiba and they should not have fakes (thus they should have NOS)...well, i ordered a couple and when I get them, will attempt to split one open and see. will post pics. if the 1302's are good I'll use them, if not then i'll use the 1943's, and if THOSE are fake..i guess i'll go with onsemi MJL1302. I wanted to keep the transistor as close as possible to original to avoid any unintended affects on the amp..

Yep, that looks like original. All the fakes seem to have the chip covered in a white silicon stuff.

Cheers

Did'nt original 1302's come is green packaging?

 

[crippledchicken]

if you haven't yet, i'd be sure to check all drivers as well

 

[nick78]

well, i'm not much of an electronics genious (though i imitate a good one). i could desolder all the drivers but...man, it's a pain.

The amp design uses a pair of NPN/PNP each paralleled. When I removed the shorted 1302, I ran the amp on the one remaining 1302 (test purposes only) and it sounded fine...so i'm assuming everything else is good...(fingers crossed). it's a subwoofer amp.

I got three new 2sa1302's from digikey, and sacraficed one for "testing" purposes. am happy to report it's a real one. see attached image.

 

[nick78]

I've attached the schematic in case anyone has any pointers on other things to test, even though it sounds like it's working great.

JP1 and JP2 lead to "down converters" whatever that means. it's a bunch of additional circuitry that looks like it's meant to play tricks with the rail voltages. The outputs of these component circuits connect at JP1 and JP2 and are labeled "(+) delta V out" and "(-) delta V out"

 

[dmfraser]

2S1302 available

We used this transistor in our amplifiers for several years. I have several scrap boards with these on them, where they appear to be good. I am sure these are NOT counterfeit parts.

I will ship one of these boards at no charge other than postage or UPS to you. There may be an NPN or two on them as well.

Contact me at chuckles951@yahoo.com. I am in Southern California.

 

[jcx]

i really don't think you want to replace just one output device - without emitter resistors the only hope is very, very good matching, such as you could at least hope for with 2 devices from the same manufacturing lot

 

[nick78]

so, i'd be better to replace all four final output transistors? How would I know any better/worse if all four new devices were matched?

I only replaced the failed one. I didn't think it'd be too bad, because it is paralleled with another 1302 (so any differences in the new 1302 should be 50% counteracted by the parallel'd device), plus it's a sub amp, ~ 80hz and below only, and human hearing isn't that accurate down there.

At least..that was my reasoning. is there anything I'm missing?

 

[Centauri]

Due to differences in the transistors, one transistor will tend to hog all the current, leaving the other one(s) doing very little. While not a problem at low volumes, high volumes can overload the hogging transistor causing it to fail (and probably taking something else with it).

Usually most power amps like this will have low value, high wattage resistors (0.1 to 0.5 ohm, 2W or 5W) in the emitter lead of each output device, which tends to promote even current sharing between the outputs. As this amp does not have those, matching of the outputs is more critical.

Cheers

 

[nick78]

well, I can certainly see the logic in that. bummer that i put the amp/enclosure all back together and have it in place - actually it's running right now.

since matching is critical with this topology, it sounds like I'd be better off getting the MJL1302/3281 matched pair from audiochips and asking if they can match me two pairs so that all four output devices match each other.

any reason why the specific schematic/topology i posted woudln't like the 1302/3281 from OnSemi?

 

[K-amps]

well, I can certainly see the logic in that. bummer that i put the amp/enclosure all back together and have it in place - actually it's running right now.

since matching is critical with this topology, it sounds like I'd be better off getting the MJL1302/3281 matched pair from audiochips and asking if they can match me two pairs so that all four output devices match each other.

any reason why the specific schematic/topology i posted woudln't like the 1302/3281 from OnSemi?

The ON parts are different from the Toshiba parts in a few parameters. cob hfe etc.

If I were to do it, I'd replace the entire OP stage with Toshiba's own 5200/1943 replacements. These are closer to the 1302's than ON's MJL1302 etc.