2sk77

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#21
It may be possible that someone is making the Yamaha part and repacking it into a modern case, or someone is re-labeling a modern SIT, or even one which is out of production but has been stockpiled or the remaining stocks bought off...

Has anyone ever opened a defective 2SK77? BTW there was also a complementary part, the 2SJ27... only made as samples. Yamaha did not use it for any of their production amps.
 
#24
Yamaha 2SK77 outline like DELCO-GM DTS-720:

It seems, that some vintage transistors from DELCO-GM uses the same outline than the Yamaha V-FET 2SK77 - have a look to post #29 about
http://www.diyaudio.com/forums/parts/167680-vintage-transistors-3.html
and the attached jpg file.
The transistors from DELCO are BjT's and no V-FET's, but if the outline was the same, and the CE voltage is enough, I would use it after the appropriate circuit modifications.
Who knows, where I get data books from Delco (Radio Delco Semiconductors) ??
 

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#30
Hi,
they are very close to triodes.
With no bias you are likley to have a D-S short.
To test apply a negative voltage (under 15V) to G with respect to source and check that D-S measures high resistance.
When starting on a B1 it's a good idea to disconnect power supply from output transistors and first of all make sure the negative bias is within right values. (With no bias the output transistors would be fully conducting to their death.)
 
#32
hi SDS, thanx for the tip, they are NOT shorted !!!


I really think that repairing this unit is more a labor of love, and I doubt that the owner is willing to pay for this kind of "over haul", asi it seems it has to be...

anyone interested in buying this amp AS IS ??

I live in Mexico city , shipping cost would be an expensive one...
 
#33
rubli said:
I really think that repairing this unit is more a labor of love,
Click to expand...

Yes indeed. It truly is a labour of love but well worth it. I got one of these a few months back and lovingly DIY'ed it back up to spec and now it's repaying me with its sweet sonics. I got it for a third the price they usually sell for because it was in pretty rough shape. It spend most of its life as a bar amp and when I got it it wasn't very far away from becoming a boat anchor which would have been a damn shame since the B-1 is such a fine piece of sonic work and very unique. Luckily it found its way to me and I was more than happy to give it the TLC it deserved.

Here are a couple of pictures the seller posted before I got it:

attachment.php


attachment.php
 

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#34
#36
rubli said:
hi SDS, thanx for the tip, they are NOT shorted !!!


I really think that repairing this unit is more a labor of love, and I doubt that the owner is willing to pay for this kind of "over haul", asi it seems it has to be...

anyone interested in buying this amp AS IS ??

I live in Mexico city , shipping cost would be an expensive one...
Click to expand...

I would give anything for one of the 2SK77 Vfet's. Is the amp still for sale?
 
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