YAMAHA B1 AMP 2SK77

[Yamahear]

Originally Posted by downandy

PLEASE TELL ME MORE ABOUT THESE PARTS FOR THE YAMAHA B1, and anything on the board extenders.
Thank You
Andy

I think tiefbassuebertr is just playing with our emotions ...

Sadly, by now it's a well established fact that when it comes to 2SK77's there's nary a one to be found on the entire planet.

[Yamahear]

Originally Posted by anatech

I was a young tech when these things were running around the earth.

Me too. Back then I was part of a Yamaha (and others) warranty depot/audio repair shop and I couldn't even afford the price of thinking about getting one of those ultimate Yamaha amps. These days, with the outputs being virtual unobtainium and B-2's being far more affordable and sustainable, I went that way instead and I have absolutely no regrets. For less than the price of a functioning B-1 I got 2 fworking B-2's and completely reconditioned them.

[djk]

"and anything on the board extenders."

Contact Yamaha to see if they are still available.

[Yamahear]

Originally Posted by downandy

but with those gargantuan T03 VFET devices I'll wait to find someone who knows.

Since this is diyAudio if you have a DVM with a diode check function, before you go to the expense of having someone else test them, it's pretty easy to check those gargantuan T03 N Channel V-FET unobtainiums. The B-1 is very modular and the heatsink assembly pull out easily. Once you have them out you can test them right on the heatsinks.

[djk]

They measure as a short until you apply a bias voltage (depletion mode).

[downandy]

THANK YOU!! Iam still a little afraid cause someone said that you can blow them easily. I've already taken out the Ch. A
(+)_(-) and did the diode test but even after drawing it out to test at the connector I forget where I've been (sumthin to do with aging) Or I just get too excited that they might be working!$$

[tiefbassuebertr]

Originally Posted by Yamahear

I think tiefbassuebertr is just playing with our emotions ...

From which you think that?

[Yamahear]

Originally Posted by tiefbassuebertr

From which you think that?

So sorry! I had you confused with sakis. I think he's playing with our emotions.

[Yamahear]

Originally Posted by downandy

THANK YOU!! Iam still a little afraid cause someone said that you can blow them easily.

Yes it's possible that you can damage them by mishandling but not too likely since V-FETs are not nearly as sensitive as MOS FETs; I've tested lots of TO-3 V-FETS by the method below without doing any damage to them.

To test them, first start by setting your DVM to the lowest ohms range. Connect the meter directly between the Drain and the Source leads and your meter should display a reading of around 5 ohms or so regardless of meter polarity. If you get a really low reading like 0.01 ohms or less or you get an open circuit reading they are likely damaged.

Next switch the meter to the diode test mode and connect the positive meter lead to the Gate and the negative meter lead to either the Source or Drain. You should see a forward biased diode drop like 0.500 ~ 0.700 mV between Gate and Source and between Gate and Drain if the FET is good. Next do the same testing with reverse polarity of the meter leads and your meter should show infinity or an open circuit depending on how your meter functions.

If you get these types of measurements the FETs are most likely still good.

I've attached a page from the B-1 owners manual that gives some data on these wonderful devices just for fun. I hope they're still good and let us know what you find.

[tiefbassuebertr]

Originally Posted by Yamahear

So sorry! I had you confused with sakis. I think he's playing with our emotions.

Thank you for clarifying.
Observe this thread from time to time concerning news for a possible reintroduce of such V-FET's:
Successors for V-FET SONY-Yamaha-TOKIN 2SJ28, 2SJ18/2SK60, 2SJ26/2SK76 and 2SK180