I worked on several of these guys years ago, and remember finding so many bad solder joints that my best recommendation is to remove *all* the solder from *all* the PCB joints and resolder. Decades of heating and cooling cycles are hard on solder joints, and there's lots to go wrong in a B-1.
All good fortune,
Chris
All good fortune,
Chris
WOW first this would explain all the problems that I've seen. But it goes against my long time respect for a company that has gone quite far to stand out as one of the best around. Having said that you must allow that my viewpoint was from the late seventies focused on the music retail buisness with a prefaced at Cerwin Vega, where Yamaha came and visited the factory, bearing gifts of thier current line only to see a few years later all of the Cerwin Vega technology in Yamaha's new line.
Sorry to say my eyesight has gone bad (must have been all that loud rock and roll) so it's difficult to find and resolder any joints.
Thank you for your reply it will help in my venture.
ANDY HILL
Sorry to say my eyesight has gone bad (must have been all that loud rock and roll) so it's difficult to find and resolder any joints.
Thank you for your reply it will help in my venture.
ANDY HILL
" only to see a few years later all of the Cerwin Vega technology in Yamaha's new line."
Give an example of such please.
The reverse is more likely to be true, I saw some CV that were a rip of ESS (for which they got sued) and others that had a rip of what looked like a Yamaha HF transducer.
Give an example of such please.
The reverse is more likely to be true, I saw some CV that were a rip of ESS (for which they got sued) and others that had a rip of what looked like a Yamaha HF transducer.
According to Wikipedia… ”The company was founded by aerospace engineer Gene Czerwinski (1927–2010) in 1954, and became noted for producing an 18" speaker capable of producing 130 dB in SPL at 30 Hz, an astonishing level during its time.” His first couple factories where damaged by Vibration.
To me he was a Polish genius. I worked on the HiFi speaker line for a short while in the early seventies. His cabinet designs brought out the best in signal response. From his double potty bottom HiFi cabinet to his ported and folded horn style cabinets in the Pro audio market that gave Klipshhorn (sp) a run for his money. Realizing that Electro Voice “Voice of the Theatre” was the capital design for loudspeaker use at the movies Cerwin ( as in Czerwinski) Vega blew them all away with his EARTHQUAKE designed sound system.
By being a young lad at the time I could only appreciate the “Loud is Beautiful” slogan “if it’s clean”, saw firsthand at the NAMM show how the JBL company demo room was lost in defeat with its blown sound system and heard the rumble from down the hall of Vega’s Sensurround shaking the shirt off our chest.
Now to Yamaha, the Japanese market was into copying the American products, and doing a fine job of it. But I saw what Cerwin Vega was making, just a couple of years later I was Selling Yamaha. Yes cleaned up a lot and not quite the symmetrical shape as Vega but filled with the concepts of a tuned cabinet. Then their electronic market went off the hook with clean as a Standel (you might remember Randall which was a spin off) but able to get close to that tube amp sound. Their mixers and amplifiers were state of the art for budding garage bands. And then out of a different part of the company came the B1.
You ask for an example the Yamaha S4115H PA cabinet and a cerwin vega cabinet that I can’t place the model on my fingertips but I saw it first at Cerwin Vega than it was introduced by Yamaha a couple of years later, I’m looking through my files maybe someone at DIY can help. Another was the Yamaha B`100 bass amp with a ported cabinet.
Gene was also into Amplifier design and came up with some very powerful amps. Some of which where put in front of me for use in quality control on the HiFi speaker line. That’s when I acquired the nickname “Andy the Amp blower”. We could launch a spider voice coil assembly to about 17 feet in the air! (that was before the amp would die).
More to follow
To me he was a Polish genius. I worked on the HiFi speaker line for a short while in the early seventies. His cabinet designs brought out the best in signal response. From his double potty bottom HiFi cabinet to his ported and folded horn style cabinets in the Pro audio market that gave Klipshhorn (sp) a run for his money. Realizing that Electro Voice “Voice of the Theatre” was the capital design for loudspeaker use at the movies Cerwin ( as in Czerwinski) Vega blew them all away with his EARTHQUAKE designed sound system.
By being a young lad at the time I could only appreciate the “Loud is Beautiful” slogan “if it’s clean”, saw firsthand at the NAMM show how the JBL company demo room was lost in defeat with its blown sound system and heard the rumble from down the hall of Vega’s Sensurround shaking the shirt off our chest.
Now to Yamaha, the Japanese market was into copying the American products, and doing a fine job of it. But I saw what Cerwin Vega was making, just a couple of years later I was Selling Yamaha. Yes cleaned up a lot and not quite the symmetrical shape as Vega but filled with the concepts of a tuned cabinet. Then their electronic market went off the hook with clean as a Standel (you might remember Randall which was a spin off) but able to get close to that tube amp sound. Their mixers and amplifiers were state of the art for budding garage bands. And then out of a different part of the company came the B1.
You ask for an example the Yamaha S4115H PA cabinet and a cerwin vega cabinet that I can’t place the model on my fingertips but I saw it first at Cerwin Vega than it was introduced by Yamaha a couple of years later, I’m looking through my files maybe someone at DIY can help. Another was the Yamaha B`100 bass amp with a ported cabinet.
Gene was also into Amplifier design and came up with some very powerful amps. Some of which where put in front of me for use in quality control on the HiFi speaker line. That’s when I acquired the nickname “Andy the Amp blower”. We could launch a spider voice coil assembly to about 17 feet in the air! (that was before the amp would die).
More to follow
The Yamaha S4115H was a generic rip of the Altec A7/JBL 4560, which were (inferior) rips of the Volkman (RCA) designs.
"Electro Voice “Voice of the Theatre”
Right, EV was barely into cinema with their Sentry IV system, the VOTT was Altec.
CV amplifier design? Most were rips from Bongiorno. There was a reason the Earthquake systems used BGW.
Enough of this, it's off-topic.
"Electro Voice “Voice of the Theatre”
Right, EV was barely into cinema with their Sentry IV system, the VOTT was Altec.
CV amplifier design? Most were rips from Bongiorno. There was a reason the Earthquake systems used BGW.
Enough of this, it's off-topic.
Last edited:
If it were mine I would first take out the driver boards and the output V-FET modules. With those removed I would power it up and check the power supplies for proper voltages, especially the -200V bias supply. Recapping the power supply and protection boards would be a good investment too.
I can't imagine having a B-1 just sitting around doing nothing for 15 years ...
Attachments
Hi
got the same finding in Yamaha 760 MKII.
I marked ~7 bad solders and decided to solder again the solders looked like heated (mat darker solder).
After all I heard the sound for a while and then it disappeared.
I suspect that output rely is in not well mechanical state.
I have similar problems with output rely and source switching in Yamaha A1.
Substitutes for 2SK77 (or any D-FET)
Hi
It is possible to repair these with modern FETs instead of the 2SK77's, but it takes a long time (weeks!) due to multiple failures that are consequences of the output devices blowing. The schematics are also wrong around the driver/output stages.
A VFET can be made from a Enhancement MOSFET by adding a couple of resistors. Essentially a 39K from Drain to Gate and 6K8 from Gate to the original gate drive. I used a pair of 2SK1058s to replace each 2SK77. I think fan cooling is also advisable.
You need to make sure that all of the protection circuits are working (in a logical order), otherwise you end up blowing up the repaired output stage. This usually means replacing all of the power transistors that switch the B+/B- supplies in after warm up. The protection circuits for each side are cross coupled, so if B+ is shorted, then B- is switched off.
I ended up with a bag of about 30 transistors that had blown before getting it working again.
The main problem is that the Yamaha has +/- 90 V power supplies, so is capable of delivering extremely high peak currents. Even testing the current limit protection is scary, as the shorting wire can vaporise when you touch it on the B+!. The -200V (from -300V) supply is also scary.
If you just want to use the power supplies, then they are usually too high voltage for most circuits. The issue is getting rid of a lot of heat- though fans help.
Arthur
Hi
It is possible to repair these with modern FETs instead of the 2SK77's, but it takes a long time (weeks!) due to multiple failures that are consequences of the output devices blowing. The schematics are also wrong around the driver/output stages.
A VFET can be made from a Enhancement MOSFET by adding a couple of resistors. Essentially a 39K from Drain to Gate and 6K8 from Gate to the original gate drive. I used a pair of 2SK1058s to replace each 2SK77. I think fan cooling is also advisable.
You need to make sure that all of the protection circuits are working (in a logical order), otherwise you end up blowing up the repaired output stage. This usually means replacing all of the power transistors that switch the B+/B- supplies in after warm up. The protection circuits for each side are cross coupled, so if B+ is shorted, then B- is switched off.
I ended up with a bag of about 30 transistors that had blown before getting it working again.
The main problem is that the Yamaha has +/- 90 V power supplies, so is capable of delivering extremely high peak currents. Even testing the current limit protection is scary, as the shorting wire can vaporise when you touch it on the B+!. The -200V (from -300V) supply is also scary.
If you just want to use the power supplies, then they are usually too high voltage for most circuits. The issue is getting rid of a lot of heat- though fans help.
Arthur
Hi voodolounge,do you still use the B1 amplifier? can you help check the 2sk77 B+ voltage and the electric current go through 2sk77.thanks.Leo
Bringing up an old Yamaha B1
Hi
My suggestion is to check the amplifier in stages. However, you will need to be an experienced electronics engineer to do this, and there are plenty of lethal voltages inside the B1, some of which remain for weeks. It's a big job, and you will need the service manual, as it has a complete set of ordered instructions. Only when all of the supplies and protection circuits have been tested, and the biases set low, should the output transistors be added. Also, as the Yamaha does not have bleed resistors on its main supplies (which I added), the main caps can remain charged for weeks. Thus, plugging in boards can be dangerous and blow things up. If you are unsure about anything (and the schematics don't help much as there are errors particularly around the driver stages), then beware.
It's a nice amp once working, though!
Good luck
Arthur
Hi
My suggestion is to check the amplifier in stages. However, you will need to be an experienced electronics engineer to do this, and there are plenty of lethal voltages inside the B1, some of which remain for weeks. It's a big job, and you will need the service manual, as it has a complete set of ordered instructions. Only when all of the supplies and protection circuits have been tested, and the biases set low, should the output transistors be added. Also, as the Yamaha does not have bleed resistors on its main supplies (which I added), the main caps can remain charged for weeks. Thus, plugging in boards can be dangerous and blow things up. If you are unsure about anything (and the schematics don't help much as there are errors particularly around the driver stages), then beware.
It's a nice amp once working, though!
Good luck
Arthur
I have a B1 with UC1-C meter and connecting cable in my garage. The B1 has one bad channel. I took it in back in late 80's and they wanted $300 to repair so I waited. Seems I waited too long. I would love to get mine fixed as it is the best sounding amp I have ever heard. But now, I cannot find any 2SK77's. So, if anyone want's everything, make an offer. Or, I will buy your bad B1, providing it has at least one good channel.
In the late 70's I was working part time selling relatively high end stereos: Tandberg, Denon, Rotel, Stax etc. ,but then one day went to a competing store to see what they had. Well,it's weird how memory works: I don't remember what I ate for breakfast a couple of days ago. I do however remember the demo room equipment setup that day at the competitor. They had the B1 connected to big ADS speakers with a Linn Sondek/Denon DL103 moving coil playing some nice,clean "direct-to-disc" classical recording. I was floored. Silky smooth buttery sounds came out of that setup. It etched a permanent sound image in my brain. No doubt the B1 had a lot to do with it.