Help identify 20+ year old MOSFETs?

Lawnmower1

Member
2013-05-21 8:17 pm
Still working on freshening the 20+ year old B&K M-200 Monoblocks, and would like to know what these output devices are, just for future reference. Unfortunately, I'm not in a position to take a picture of them, so I'll try to describe them as accurately as possible.

There are a total of 20 of them in the amp. 10 gray in color, 10 green, so it's likely that they're complimentary P and N channel. They're all in TO-247 style packages. None has much in the way of identifying markings. The gray ones have a large "T" on the top, "K405" on the second line, and "Y___1G" on the third line. The green ones start with the same "T", followed by "J115", and then "Y___1F" That's it.

Anyone shed some light on these?

Many thanks.
 
Holy cow. Should have invested in those things when the buying was good. Thanks for the information. Those are indeed what's in the amp, in large quantities. I guess, from the discussion in the thread you mentioned, that there are no replacements for these things. I guess also that I'm going to be even more careful than usual in updating the old caps in this amp.

Thanks again.
 
...I guess, from the discussion in the thread you mentioned, that there are no replacements for these things...
There are replacements for almost everything... however since they are not always exact replacements, you may have to replace another simple component or two, like a gate resistor, or reset the bias current or something like that. Old circuit boards are actually easier to work with than new ones (bigger components, further apart, fewer or no ICs). Someone else may know exactly what you need. When you are done, it may even sound better... :D Besides, if they work, they are probably nicely burned in after twenty years, so why replace them?
 

Lawnmower1

Member
2013-05-21 8:17 pm
Thanks loads for the helpful replies, guys. I've been away from this stuff for a while and it looks like I've missed a few entire generations of parts! BTW, the 2SK1529/2SJ200 are EOL'd now and essentially impossible to find. The next generation of those is 2SK1530/2SJ201 and THEY are EOL'd too. There are a few of them floating around out there, none of which are being sold by what I consider unimpeachable (i.e. Mouser, Allied, Newark, Arrow...) sources. And Ebay is about the last place I'd consider buying anything like this. Those characters that ship from Hong Kong or wherever don't hesitate to remark other parts from what I've seen.

I also went directly to Toshiba's site and found nothing like these transistors in production now. Here is their MOSFET lineup. You'll find all kinds of switching transistors for power supplies and lighting, but they appear to be done with the audio power market segment.

While the originals in my amps are still working, I'd feel a bit better having a small bag of compatible replacements in stock, so I'm going to keep looking.