AU-20000 Output Transistors

[Rotoflex4]

Good afternoon,

On one side of my amp I have the original transistors (3 x Sanken 2SA908 and 3 x Sanken 2SC1585). They appear to be fine.

On the other side one 2SA908 has previously been replaced by a Toshiba 2SB554, and one 2SC1585 has been replaced by a Toshiba 2SD424 (the 2SD424 is currently dead). So....I need to do some replacing. I've read that it's desirable to replace them as sets. Therefore I would like to replace all six on the one side (3 x MJ21194 and 3 x MJ21193).

Is this a reasonable approach? I'd like to leave the six good ones on the other side alone if possible, or is it necessary to replace all twelve?

Thanks.

-Will

 

[Hipocrates]

Better replace all of them.
I don't think it will be a problem using the ''slower'' MJ21193/94, but let's see what some people which had work on that amp says.

 

[Rotoflex4]

Some say that the original Sankens are superior, and others say that the newer ones are best (for dependability at least if not performance). If I could just locate one used 2SA908 and one 2SC1585 (easier said than done) I'd be in good shape. If swapping means doing all 12, and possibly having parts that are inferior to the originals, then used might be an option.

 

[AUD101]

Another possible solution is to sub the Sanken 2SA908's & 2SC1585's with Sanken NOS 2SA1116's & 2SC2607's - both available from the Sansui Parts shop - Netherlands

 

[w1jim]

Would a set of 2SA909/2SC1586 work?
They appear to be the same except they're rated 50 volts higher.
I know a guy who would be eager to see another AU-20000 preserved.

 

[AUD101]

Yep, the 2SA909/2SC1586 will work as well

 

[Rotoflex4]

Could I just swap out 2 transistors with these Sanken replacements (2SA909 and 2SC1586), or would I need to replace them all in order to have a matched set?

 

[Hyperion]

Could I just swap out 2 transistors with these Sanken replacements (2SA909 and 2SC1586), or would I need to replace them all in order to have a matched set?

All in one channel definitely - only 2 types, no mixing - this is very important.

Personally I would be very much inclined to use a new set of On-Semis - but that's just me

 

[DougBrewster]

here's a thought. I'm in the middle of a G871DB refurb. It's a working unit (at least it was) and has a complement of 2SA908 and 2SC1585 outputs except that one of the 1585s has been replaced with a 1586. I'm mooching around for info on the suitability of replacing them with MJ21193/94s and if it seems a good idea there may be a bunch of 908s and 1585s coming available...

 

[Rotoflex4]

Thanks, Doug. I decided to go with MJ21193/94s after all. Started installing them today. We'll see how that works.

 

[The Fuxtor]

Wondering how this all worked out??
Raise the zombies!!!!