MJ21193 and MJ21194

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Member
2013-03-11 10:52 am
Thinking of using these to replace my 2SD287C and 2SB539C output in my Pioneer SX-1050 AMP, anybody have suggestions? comments?:D

Yes, those are the correct transistors to use. And the only valid option available. They are drop-in replacements, but you have to replace all of them.

Anything else you use will be fake or unsuitable to the job.

You've been adviced to use NTE parts - never do this. Just google NTE transistors and you'll see the horror stories.
 
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Wrong ...there is more parts that are closer to the originals ...It is very common in the forum that the only available option is 21193- as was in the past MJ15024

You need to look better
2SC4467-2SA1695 is much closer replacement by far easier to fit commonly available plus that these are easier load and much faster so after all you are going to have a bit better amplifier

Going to that type of change you need to scope the all thing since compensation might needs to be altered ( in most cases you will get away with it...)

there could more similar to those

Kind regards
Sakis
 
Wrong ...there is more parts that are closer to the originals ...It is very common in the forum that the only available option is 21193- as was in the past MJ15024

You need to look better
2SC4467-2SA1695 is much closer replacement by far easier to fit commonly available plus that these are easier load and much faster so after all you are going to have a bit better amplifier

Going to that type of change you need to scope the all thing since compensation might needs to be altered ( in most cases you will get away with it...)

there could more similar to those

Kind regards
Sakis
They seem to be cheap and readily available here in Australia but I noticed the 4467 are only 8A collector. Would I be sacrificing power? I don't mind rewiring for this package. Thanks again
 
Yes, those are the correct transistors to use. And the only valid option available. They are drop-in replacements, but you have to replace all of them.

Anything else you use will be fake or unsuitable to the job.

You've been adviced to use NTE parts - never do this. Just google NTE transistors and you'll see the horror stories.
So you recommend these? They seem to be the only genuine article I can find to replace the old ones after being taken by Chinese knock offs before... Would the sonics be as good in your opinion? Cheers
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
The SX1050 has 2 pairs of output transistors for 170W/4R rating so the SOA of 2SC4467 could be a bit small. You can buy alleged NOS and Chinese TO3 copies of Japanese types but what guarantees do you have? BTW, 2SC4468 looks closer in SOA to the 2SC287C but is probably harder to find. I'm inferring the PNP complements are included in comparisons.
2SD287C PDF Datasheet - NEC Corporation - Datasheets360.com
http://www.semicon.sanken-ele.co.jp/sk_content/2sc4468_ds_en.pdf
Whilst considering T03P package replacements, genuine spec. 2SD1047/B817 might be more suitable. KEC copies are close enough to original spec.

After 40 years, I assume this receiver has had at least 1 full re-cap. of electrolytics. If not, I would look at replacing all and certainly those in the output protection circuit, so at least that works correctly to protect the replacement transistors. NTE, BTW, has a bad rap in the US.
 
The SX1050 has 2 pairs of output transistors for 170W/4R rating so the SOA of 2SC4467 could be a bit small. You can buy alleged NOS and Chinese TO3 copies of Japanese types but what guarantees do you have? BTW, 2SC4468 looks closer in SOA to the 2SC287C but is probably harder to find. I'm inferring the PNP complements are included in comparisons.
2SD287C PDF Datasheet - NEC Corporation - Datasheets360.com
http://www.semicon.sanken-ele.co.jp/sk_content/2sc4468_ds_en.pdf
Whilst considering T03P package replacements, genuine spec. 2SD1047/B817 might be more suitable. KEC copies are close enough to original spec.

After 40 years, I assume this receiver has had at least 1 full re-cap. of electrolytics. If not, I would look at replacing all and certainly those in the output protection circuit, so at least that works correctly to protect the replacement transistors. NTE, BTW, has a bad rap in the US.
Thanks Ian, yes I know what you mean about Chinese fakes I bought replacements completely unaware of the market in fraud devices and promptly fried 4 of the original transistors because I mixed and matched original and fakes. Only needed 2 originally but now I only have 2 original ones left which work one channel fine at half power. I bought some b539 from a chap in America but they are not the C variety. Only difference I can see is Uce rating of 30 volts less which should be fine in this amp so really or I need is 287s to complete it or a complete set of comparatable units. I did a full recap of the protection circuit and the lytics in the power amp. Power rails ok so left the ps alone. Those 2sd1047 and b817 look a perfect replacement. And available from wes in oz. should I go and buy enough to match up pairs Ian? Much obliged. Might just get this working again soon! :)
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
I would buy as many as I could afford if satisfied that the parts are good quality. Otherwise, just 2 pairs and test one channel with a single random pair. There has to be half a dozen manufacturers of the 2SD1047/B817 that either produce good copies or they are generic types, close enough for undemanding audio applications and DIY usage. Unfortunately, there's probably more fakers that are passing off undersize or scrap dies as equal when they have no chance of working at more than a few watts. In any case, as you don't need to modify the heatsink, it should be easy enough to refit TO3 parts , should you ever find enough suitable ones in the future.

I didn't realize WES stocked these parts but regardless where you get them, try to identify the source first. WES tell you nothing in their stock parts lists and you know they will have to buy these obsolete parts from whatever second source they can get. Some Chinese copies may be fine but there is a significant increase in thermal resistance with changing to this package and you don't need some flimsy little die to fail through lack of adequate heat spreading.

As a suggestion, I always make sure I keep one channel original when testing parts you aren't certain of for any reason. Fit a light bulb limiter to the mains and compare all relevant DC measurements between power amp. channels before hitting the amplifier with signal and load. Resolve any issues before pulling the limiter out and going to full power or getting to work on the second channel. Good luck anyway :)
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
You are right Sakis, but I have been successful with several KEC pairs bought a few times in the last 2 years. I used them in a number of small PA amplifiers that get a hard life and fail a lot due to poor VI limiters. Their Ft is below the Sanyo spec. but that's not an issue here. Their plastic TO3P package is difficult to copy and the part number is not so familiar (KTD1047/KTB817) so perhaps fakers will be less successful in stealing their market.
KTD1047B_15 pdf, KTD1047B_15 description, KTD1047B_15 datasheets, KTD1047B_15 view ::: ALLDATASHEET :::
 
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You are right Sakis, but I have been successful with several KEC pairs bought a few times in the last 2 years. I used them in a number of small PA amplifiers that get a hard life and fail a lot due to poor VI limiters. Their Ft is below the Sanyo spec. but that's not an issue here. Their plastic TO3P package is difficult to copy and the part number is not so familiar (KTD1047/KTB817) so perhaps fakers will be less successful in stealing their market.
KTD1047B_15 pdf, KTD1047B_15 description, KTD1047B_15 datasheets, KTD1047B_15 view ::: ALLDATASHEET :::
Cheers again Ian. I have requested manufacturer details from wes for these, let's see what happens. This is my first semiconductor amp repair and I never thought parts would be so hard to find! Have to go back to valve amps ;)
 

TonyTecson

diyAudio Moderator Emeritus
2003-05-29 2:57 am
Maybunga, Pasig City
Thinking of using these to replace my 2SD287C and 2SB539C output in my Pioneer SX-1050 AMP, anybody have suggestions? comments?:D


i have successfully repaired japanese amps with obsolete power trannies using ON semi parts....
if left with no other options, you can try if you have them already...but in such case as yours i would use the mj15003/15004 parts...