Unda Maris
Mr. V-FET
Just another VFET ? Yes, it was time (only a few weeks until Christmas).
Where did I find it ? ..... In the Yamaha B-1 ! ..... Say what ?
It was clear, that Yamaha used the 2SK77 mammoth V-FET transistors for the output stage and 2SK75 as drivers in various stages.
No source ever mentioned the 2SJ24A to be a V-Fet, but it is definitely one.
A normal J-Fet wouldn´t stand the 150V applied to it. It´s a small signal device in a TO-39 metal can package.
And it´s a P-channel type, which shows to us, that Yamahas first generation also included such a device and not only N-channel devices.
Adding these to the list, the B-1 contains 18 V-Fets in total (of 5 types including the different rankings) ! This is no good news for people, who want to repair such an amplifier.
There is now again a little hope, that the C-1 wasn´t the only V-Fet preamplifier ever made.
Does anybody know any other gear (e.g. preamplifiers), which use this device ? Does perhaps the C-2 use it ? Does anybody have the C-2 Service manual to check it ?
Where did I find it ? ..... In the Yamaha B-1 ! ..... Say what ?
It was clear, that Yamaha used the 2SK77 mammoth V-FET transistors for the output stage and 2SK75 as drivers in various stages.
No source ever mentioned the 2SJ24A to be a V-Fet, but it is definitely one.
A normal J-Fet wouldn´t stand the 150V applied to it. It´s a small signal device in a TO-39 metal can package.
And it´s a P-channel type, which shows to us, that Yamahas first generation also included such a device and not only N-channel devices.
Adding these to the list, the B-1 contains 18 V-Fets in total (of 5 types including the different rankings) ! This is no good news for people, who want to repair such an amplifier.
There is now again a little hope, that the C-1 wasn´t the only V-Fet preamplifier ever made.
Does anybody know any other gear (e.g. preamplifiers), which use this device ? Does perhaps the C-2 use it ? Does anybody have the C-2 Service manual to check it ?