HEY I got one of thoses old/rare YAMAHA B1 stereo natural sound amplifiers that I may want to get rid of. Of course the red overprotection light comes on and no sound comes out but the METERS sure are pretty (yes the UC-1 unit). It handled a lot of great gigs at all the big places in Hollywood back in the 70's....sound incredible and VERY QUITE when it comes to noise.
I'm about to take it over to the local YAMAHA wiz and see if he can find the problem or at least tell me if the VFETS ARE good.
Any help out there?
I'm about to take it over to the local YAMAHA wiz and see if he can find the problem or at least tell me if the VFETS ARE good.
Any help out there?
Hi downandy,
Be careful here. I was an authorized warranty centre for both Yamaha home and Yamaha MI. Make absolutely sure this fellow was around back then so that he doesn't blow any up in error. Those output devices are unobtainium. The case style is even completely different from anything we have these days.
If the output devices are lost, finding other from dead amps will be both difficult and expensive. A service manual is a must! I wouldn't work on one without the manual in some format, and I've seen them before. Your amplifier is not really repairable any other way - not really. The tech should be able to determine what is blown without removing the outputs. It is possible that a fuse died of old age, or solder joints opened up. Applying power to it without solving all the problems could also blow what were good outputs. In fact, the amplifier must not be plugged in and turned on (yeah, I know you did), don't tempt fate any more than you have already. The proper power up test procedure is to use eyeballs first and look for tell tale signs of trouble. Note that this means that you do not power it up on the bench! If all looks and tests good, power can be applied by bypassing the soft start and increasing the AC line voltage slowly while watching the current meter. Note that an oxidized bias control can also destroy a set of good outputs.
If you need output transistors, the value of the amp is sadly that of a chassis to build another design of amp only. They are expensive to ship, so of low resale value on Eeekbay. Suffice to say that the person who inspects your amplifier needs to know how to work on these and also understand them well. I doubt very much a 40 year old person actually knows how to deal with these. The tech will be an old guy like me. I was a young tech when these things were running around the earth.
Be careful here. I was an authorized warranty centre for both Yamaha home and Yamaha MI. Make absolutely sure this fellow was around back then so that he doesn't blow any up in error. Those output devices are unobtainium. The case style is even completely different from anything we have these days.
If the output devices are lost, finding other from dead amps will be both difficult and expensive. A service manual is a must! I wouldn't work on one without the manual in some format, and I've seen them before. Your amplifier is not really repairable any other way - not really. The tech should be able to determine what is blown without removing the outputs. It is possible that a fuse died of old age, or solder joints opened up. Applying power to it without solving all the problems could also blow what were good outputs. In fact, the amplifier must not be plugged in and turned on (yeah, I know you did), don't tempt fate any more than you have already. The proper power up test procedure is to use eyeballs first and look for tell tale signs of trouble. Note that this means that you do not power it up on the bench! If all looks and tests good, power can be applied by bypassing the soft start and increasing the AC line voltage slowly while watching the current meter. Note that an oxidized bias control can also destroy a set of good outputs.
If you need output transistors, the value of the amp is sadly that of a chassis to build another design of amp only. They are expensive to ship, so of low resale value on Eeekbay. Suffice to say that the person who inspects your amplifier needs to know how to work on these and also understand them well. I doubt very much a 40 year old person actually knows how to deal with these. The tech will be an old guy like me. I was a young tech when these things were running around the earth.
THANKS AUDIOHEAD AND ANATECH
I know that these are a pain, I started to take it apart and then got smart.....twenty years later! The fuses look good (13?) and I don't see any external device damage. I now have a service manual and a hope and a prayer that the overload protection circuit is at fault but with those gargantuan T03 VFET devices I'll wait to find someone who knows. You got me stuck on the oxidized bias control. And I thought everyone was younger than me! When this amp came out I was just a kid playing Rock and Roll in Hollywood!
I know that these are a pain, I started to take it apart and then got smart.....twenty years later! The fuses look good (13?) and I don't see any external device damage. I now have a service manual and a hope and a prayer that the overload protection circuit is at fault but with those gargantuan T03 VFET devices I'll wait to find someone who knows. You got me stuck on the oxidized bias control. And I thought everyone was younger than me! When this amp came out I was just a kid playing Rock and Roll in Hollywood!
check out this threads:
http://www.diyaudio.com/forums/soli...to3-like-yamaha-2sk77-nec-2d363-overview.html
http://www.diyaudio.com/forums/solid-state/74774-2sk77.html
http://www.diyaudio.com/forums/chip-amps/157618-vfet-hitachi-2sk77-2sk76-2sj26.html
http://www.diyaudio.com/forums/soli...kin-2sj28-2sj18-2sk60-2sj26-2sk76-2sk180.html
http://www.diyaudio.com/forums/soli...to3-like-yamaha-2sk77-nec-2d363-overview.html
http://www.diyaudio.com/forums/solid-state/74774-2sk77.html
http://www.diyaudio.com/forums/chip-amps/157618-vfet-hitachi-2sk77-2sk76-2sj26.html
http://www.diyaudio.com/forums/soli...kin-2sj28-2sj18-2sk60-2sj26-2sk76-2sk180.html
I guess, the price of 48 euros/pc is very very cheap for a 2SK77 in new condition. Please let me know the provider/supplier.
Keep in mind - the user does not have the intention to obtain an inexpensive amplifier for cost effectice repair. Rather the desire, to get the original/genuine condition after repair service is the most important thing.
here additional links:
http://my.coolala.net/upload0713/2010/281/1286557087.gif
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I??????????? - ??????Blog?
???????? - ????Miyuki.Taira?????
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2SK77
PLEASE TELL ME MORE ABOUT THESE PARTS FOR THE YAMAHA B1, and anything on the board extenders.
Thank You
Andy
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.
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.
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.
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!$$
(+)_(-) and did the diode test but even after drawing it out to test at the connector I forget where I've been (sumthin to do with aging) Or I just get too excited that they might be working!$$
From which you think that?I think tiefbassuebertr is just playing with our emotions ...
So sorry! I had you confused with sakis. I think he's playing with our emotions.
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.
Thank you for clarifying.So sorry! I had you confused with sakis. I think he's playing with our emotions.
Observe this thread from time to time concerning news for a possible reintroduce of such V-FET's:
http://www.diyaudio.com/forums/soli...kin-2sj28-2sj18-2sk60-2sj26-2sk76-2sk180.html