Oh wow,
I don't think those transistors are available any more. Totally different case style. Try and find another amp with a dead channel. Also, look up an old Yamaha warranty shop that may have the manual. They may even have a "dead thing" lying around for parts.
Don't forget to check with Yamaha directly.
-Chris
I don't think those transistors are available any more. Totally different case style. Try and find another amp with a dead channel. Also, look up an old Yamaha warranty shop that may have the manual. They may even have a "dead thing" lying around for parts.
Don't forget to check with Yamaha directly.
-Chris
"Totally different case style. "
That was the B1,
"Was that the amp that used power JFETs? "
the B2 used complementary TO3 power JFETS.
Right now on eBay are three different auctions for B2 amplifiers, and some guy selling shop manuals for same.
Real nice chassis, dual mono construction, ±57V, big sinks, great meters.
It should be possible to put in BUZ900/905, reverse the gate drives, and re-bias.
That was the B1,
"Was that the amp that used power JFETs? "
the B2 used complementary TO3 power JFETS.
Right now on eBay are three different auctions for B2 amplifiers, and some guy selling shop manuals for same.
Real nice chassis, dual mono construction, ±57V, big sinks, great meters.
It should be possible to put in BUZ900/905, reverse the gate drives, and re-bias.
djk said:
Strongly disagree with this. I suppose that anything is possible, but in this case the trouble-to-worth ratio would be astronomical.
The VFETs used in the B-1 and B-2 (different devices for each, as you pointed out) are also known as "static induction transistors" or SITs. These are depletion-mode devices and require about 20 volts of negative bias. This is in contrast to the BUZ enhancement-mode devices that require less than one volt of positive bias.
One of the best sources for information on these amps was an article in Audio Magazine on power FETs by Bascom King in the mid- to late-seventies. It should be available at most university libraries.
"One of the best sources for information on these amps "
So I guess being an Authorized Yamaha Service Center, having the manuals, spare parts, the card extenders, two days of specialized instruction on these models, being tested on that knowledge, and given the Service Specialist Award doesn't mean anything.
The outputs are no longer available.
Short of gutting it for the chassis, what would you do?
So I guess being an Authorized Yamaha Service Center, having the manuals, spare parts, the card extenders, two days of specialized instruction on these models, being tested on that knowledge, and given the Service Specialist Award doesn't mean anything.
The outputs are no longer available.
Short of gutting it for the chassis, what would you do?
djk said:
I should have said "one of the best published sources of information". Besides the service manual, King's article is one of the few things ever published on these amps.
The only other information I have ever seen regarding these types of transistors are some books written by Ed Oxner, formerly with Siliconix. However these specialized publications are quite expensive, over $100 per book.
djk said:
You obviously have more hands-on experience than I do with these amps. Still, I would be extremely reluctant to replace the thing (VFETs) that made them unique. Even disregarding the radically different bias requirements, the VFETs are very triode-like, while the MOSFETs are very pentode-like. I would anticipate that such a transformation would significantly change the sonic performance of the amp. Have you successfully performed such a mod?
I suppose I would try a few approaches:
a) Try to find some output devices. I haven't done a thorough search, but some must be available somewhere. If all else fails, one could purchase a complete amplifier on e-Bay for around $250 and use one of the units for spare parts. This would be much easier (and probably cheaper) than trying to re-design the unit to use (radically) different output devices.
b) Sell the amp (or at least the output devices) to someone that needs spare parts and buy/build an amp using easily available parts.
c) Hold your breath and wait until Toshiba puts the silicon-carbide based SITs (SIT = VFET) into production:
http://www.semicon.toshiba.co.jp/release/exhibition/its/pdf/sic_presen.pdf
unobtianium
I guess we are back to buying a unit for parts or selling your unit for same.
djk, weren't they fun to work on? Darn outputs were super expensive when they were available. I gave one of these away about 8 years ago for that reason. Most people will not value this unit, so you should be able to get one cheap. (per pound as it were).
elviukai, I'd like to see you fix it, the unit is worth it. Just having it working would be really cool.
-Chris
I guess we are back to buying a unit for parts or selling your unit for same.
djk, weren't they fun to work on? Darn outputs were super expensive when they were available. I gave one of these away about 8 years ago for that reason. Most people will not value this unit, so you should be able to get one cheap. (per pound as it were).
elviukai, I'd like to see you fix it, the unit is worth it. Just having it working would be really cool.
-Chris
Re: v-fets
The 2SK134/2SK135/2SJ49/2SJ50 is power MOS-FET and not V-FET.
About V-FET, You can refer below url:
http://www.thevintageknob.org/VFET/1975/VFET75.html
elviukai said:
The 2SK134/2SK135/2SJ49/2SJ50 is power MOS-FET and not V-FET.
About V-FET, You can refer below url:
http://www.thevintageknob.org/VFET/1975/VFET75.html
You can order service maunal from Service-Manuals.net:
http://service-manuals.net/manuals/y/yamaha/yamaha.htm
http://service-manuals.net/manuals/y/yamaha/yamaha.htm
v-fets
there are no V-fet on the market?
so why normal mosfet cost 54eur/each in local shop??? for comparing they have irfp 0xx/1xx/2xx from 1 to 2 euros..
BtW I hooked this one channel to dynaudio diY speakers(mw 170, tweeter - ribbon, x over at 4khz) yamaha for a longer time- looks like it was conected long time ago. what can I say.. the sound now is mych better, it has some very interesnting openess in midrange, an has incereirble HUGE macrodynamic, very fast and powerful and at the same tie subtile sound.
pretty sad to take in parts this beauty- silver colour mint..
two v-fets is probably good in dead chanel- I suppose can not repalce only two(there are 4 per chanel) dead?
how about sound qyality if repalce with ordinary mosfets ,and what sugestions about it? irfp 240 will not fit..
also I am thinking of selling this heavy thing, for somebody near lthuania. , europe, because it weight 28kilos.
there are no V-fet on the market?so why normal mosfet cost 54eur/each in local shop???
for comparing they have irfp 0xx/1xx/2xx from 1 to 2 euros..BtW I hooked this one channel to dynaudio diY speakers(mw 170, tweeter - ribbon, x over at 4khz) yamaha for a longer time- looks like it was conected long time ago. what can I say.. the sound now is mych better, it has some very interesnting openess in midrange, an has incereirble HUGE macrodynamic, very fast and powerful and at the same tie subtile sound.
pretty sad to take in parts this beauty- silver colour mint..
two v-fets is probably good in dead chanel- I suppose can not repalce only two(there are 4 per chanel) dead?
how about sound qyality if repalce with ordinary mosfets ,and what sugestions about it? irfp 240 will not fit..
also I am thinking of selling this heavy thing, for somebody near lthuania. , europe, because it weight 28kilos.
The Hitachi MOSFETs (2SK135 + 2SJ50) are lateral types designed for audio. The Toshiba MOSFETs (2SK1530 + 2SJ201) are vertical types designed for audio. The International Rectifier MOSFETs (IRFxxx) are vertical types designed for switching power supplies. None of these can substitute for the VFETs found in your Yamaha amplifier.
The Hitachi parts mentioned are very expensive because they have been discontinued for about 10 years. They have the same die in a plastic package (2SK1058 + 2SJ351) for around $5 each. Improved clones of the Hitachi parts are available in both plastic and metal packages from Magnatec (also known as Exicon) for $5 to $10 each.
The Hitachi parts mentioned are very expensive because they have been discontinued for about 10 years. They have the same die in a plastic package (2SK1058 + 2SJ351) for around $5 each. Improved clones of the Hitachi parts are available in both plastic and metal packages from Magnatec (also known as Exicon) for $5 to $10 each.
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