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Yamaha B2 - the "why" and the "how" of a comprehensive rebuild

Hi, everyone! After getting my hands on a Sony TA N7b amplifier, I dove into the world of V-FETs. And now I have this wonderful restored Yamaha B-2 in my system. After three days of listening, I’m absolutely thrilled and want to thank our friend US7IGN here, who showed me this article and carried out all the restoration work with great professionalism. Of course, I also want to thank Mr. rottalpha , who developed this project and shared it with us. It was a long and difficult project with complicated logistics for shipping the necessary parts, but friends from all over the world helped out with that. I can confidently say that this Yamaha B-2 outperforms my own restored US7IGN Sony TA N7b and Sony TA 8650. Everything written here about the sound of this amplifier is absolutely true. Even a simple source like an FM tuner paired with Sony SS G7 speakers produced a whole new level of sound quality! During the restoration process, it turned out that rust had formed under one of the transformers, which I managed to fix by galvanizing it, as other users have shown here. In the future, I plan to upgrade the backlighting with an LED strip. I’m really happy that the transistors in my black Yamaha B-2 turned out to be intact. And I hope we have another project ahead of us to save this amplifier! For anyone interested, here’s a link to the article about the restoration: Yamaha B-2 restoration




1779366172209192.jpg177936622789552.jpg1779366230842681.jpg123.jpg
 
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Virtus said:
Hi, everyone! After getting my hands on a Sony TA N7b amplifier, I dove into the world of V-FETs. And now I have this wonderful restored Yamaha B-2 in my system. After three days of listening, I’m absolutely thrilled and want to thank our friend US7IGN here, who showed me this article and carried out all the restoration work with great professionalism. Of course, I also want to thank Mr. rottalpha , who developed this project and shared it with us. It was a long and difficult project with complicated logistics for shipping the necessary parts, but friends from all over the world helped out with that. I can confidently say that this Yamaha B-2 outperforms my own restored US7IGN Sony TA N7b and Sony TA 8650. Everything written here about the sound of this amplifier is absolutely true. Even a simple source like an FM tuner paired with Sony SS G7 speakers produced a whole new level of sound quality! During the restoration process, it turned out that rust had formed under one of the transformers, which I managed to fix by galvanizing it, as other users have shown here. In the future, I plan to upgrade the backlighting with an LED strip. I’m really happy that the transistors in my black Yamaha B-2 turned out to be intact. And I hope we have another project ahead of us to save this amplifier! For anyone interested, here’s a link to the article about the restoration: Yamaha B-2 restoration




View attachment 3766660View attachment 3766658View attachment 3766655View attachment 3766656
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Congrats!
it is a gorgeous amplifier. The real "music to my ears" is hearing how you and your friend saved all those v-fet amps.
 
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rottalpha said:
Congrats!
it is a gorgeous amplifier. The real "music to my ears" is hearing how you and your friend saved all those v-fet amps.
Click to expand...
Thanks, Peter! Your videos and articles on properly restoring amplifiers with V-FET transistors are a great inspiration to us. I’m still hoping you’ll apply your expertise and find a solution for the preamp section of the Sony TA 8650, just as you did with the Yamaha C-1))) For now, I’m forced to use the Sony TA 8650 as a power amp alongside the Sony TA E88 preamp, and it’s magnificent
 
Virtus said:
Thanks, Peter! Your videos and articles on properly restoring amplifiers with V-FET transistors are a great inspiration to us. I’m still hoping you’ll apply your expertise and find a solution for the preamp section of the Sony TA 8650, just as you did with the Yamaha C-1))) For now, I’m forced to use the Sony TA 8650 as a power amp alongside the Sony TA E88 preamp, and it’s magnificent
Click to expand...
I started the 8650 project but had to set it aside for lack of time. Family and my real job leave little time for my hobby.
 
Virtus said:
Thanks, Peter! Your videos and articles on properly restoring amplifiers with V-FET transistors are a great inspiration to us. I’m still hoping you’ll apply your expertise and find a solution for the preamp section of the Sony TA 8650, just as you did with the Yamaha C-1))) For now, I’m forced to use the Sony TA 8650 as a power amp alongside the Sony TA E88 preamp, and it’s magnificent
Click to expand...
quick question: Did you determined what was the issue with the preamp section of your Sony?
 
rottalpha said:
quick question: Did you determined what was the issue with the preamp section of your Sony?
Click to expand...
In my amplifier, the sound in the right channel periodically drops out by 80%. Sometimes the sound returns if I turn the amplifier off and on again. The sound might also come back if I turn the volume up very high and suddenly. But after a couple of minutes, the sound would disappear again. Replacing any parts did not yield positive results. Suspicion fell on the green BX-269 and BX-270 microchips. There is also significant overall preamp noise, which is audible in the speakers
 
rottalpha said:
I know that with the exit of Nichicon from the market, the question remains about what are the available choices for replacing the big filter cans for a Yamaha B2.
As I stated in the beginning of the thread, Kemet /Riffa and Epcos /TDK make very good alternatives. Yes not specifically designed for audio but still very good. Below are some of the series I am speaking of:

ALS30A223KE063
ALS40A223KF063
ALS70A203KF100
PEH169MK522VMB2
B41458B8229M000
B41560A8229M000
ALS36H223K3C063
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I'm currently restoring my second Yamaha B-2. To replace the filter capacitors, I chose the B41458B8229M000. Right now, it's the only option on the list that's available at Mouser (https://www.mouser.com/en/ProductDetail/TDK/B41458B8229M000?qs=DFkWJ3l%2BHdIoV0ho2MMGwg==). I asked the AI if these capacitors would work, and here's what it said:

"The voltage on the power supply buses for the V-FET transistors in the Yamaha B-2 under load is approximately ±55 V. By all standards of circuit design, the 63-volt capacitors are operating at their limit here (with a margin of only 8 V), especially given the potential for voltage spikes in modern power grids. Yamaha engineers deliberately used the uncommon 71-volt audio-grade rating to ensure a safe margin of safety. The danger of installing 63-volt capacitors: If you install the TDK/EPCOS capacitors mentioned earlier, rated at 63 V, they will operate in a critical mode. At the slightest voltage spike in the outlet (for example, if the mains voltage is 235 V instead of 220 V), the DC voltage on the power rails will rise above 58–60 V. Repair Recommendation: When replacing the original Yamaha B-2 capacitors, it is strongly recommended to choose modern capacitors with a voltage rating of at least 80 V (for example, 22,000 μF / 80 V). This will provide an ideal and safe margin of reliability for the vintage circuit. "

Peter, I'd be interested to hear your opinion on this. To what extent is the computer correct in saying that 63 V is too low for the capacitors in the Yamaha B-2?
 
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Virtus said:
In my amplifier, the sound in the right channel periodically drops out by 80%. Sometimes the sound returns if I turn the amplifier off and on again. The sound might also come back if I turn the volume up very high and suddenly. But after a couple of minutes, the sound would disappear again. Replacing any parts did not yield positive results. Suspicion fell on the green BX-269 and BX-270 microchips. There is also significant overall preamp noise, which is audible in the speakers
Click to expand...
Interesting, I'm having this same issue with my recently purchased TA-8650. And it's definitely a preamp issue, I hear the volume loss from the pre out RCA connectors. This is quite weird, it's the first time I see something similar, haven't investigated the issue yet and have no clue.
 
Virtus said:
I'm currently restoring my second Yamaha B-2. To replace the filter capacitors, I chose the B41458B8229M000. Right now, it's the only option on the list that's available at Mouser (https://www.mouser.com/en/ProductDetail/TDK/B41458B8229M000?qs=DFkWJ3l%2BHdIoV0ho2MMGwg==). I asked the AI if these capacitors would work, and here's what it said:

"The voltage on the power supply buses for the V-FET transistors in the Yamaha B-2 under load is approximately ±55 V. By all standards of circuit design, the 63-volt capacitors are operating at their limit here (with a margin of only 8 V), especially given the potential for voltage spikes in modern power grids. Yamaha engineers deliberately used the uncommon 71-volt audio-grade rating to ensure a safe margin of safety. The danger of installing 63-volt capacitors: If you install the TDK/EPCOS capacitors mentioned earlier, rated at 63 V, they will operate in a critical mode. At the slightest voltage spike in the outlet (for example, if the mains voltage is 235 V instead of 220 V), the DC voltage on the power rails will rise above 58–60 V. Repair Recommendation: When replacing the original Yamaha B-2 capacitors, it is strongly recommended to choose modern capacitors with a voltage rating of at least 80 V (for example, 22,000 μF / 80 V). This will provide an ideal and safe margin of reliability for the vintage circuit. "

Peter, I'd be interested to hear your opinion on this. To what extent is the computer correct in saying that 63 V is too low for the capacitors in the Yamaha B-2?
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it is not too low, but it is near the limit. With that said, the original ones were rated at 63V and worked for a long time.
 
spaghetti said:
Interesting, I'm having this same issue with my recently purchased TA-8650. And it's definitely a preamp issue, I hear the volume loss from the pre out RCA connectors. This is quite weird, it's the first time I see something similar, haven't investigated the issue yet and have no clue.
Click to expand...
while the reasons could vary, the primary suspects are the op-amps in the preamp section
 
Virtus said:
I'm currently restoring my second Yamaha B-2. To replace the filter capacitors, I chose the B41458B8229M000. Right now, it's the only option on the list that's available at Mouser (https://www.mouser.com/en/ProductDetail/TDK/B41458B8229M000?qs=DFkWJ3l%2BHdIoV0ho2MMGwg==). I asked the AI if these capacitors would work, and here's what it said:

"The voltage on the power supply buses for the V-FET transistors in the Yamaha B-2 under load is approximately ±55 V. By all standards of circuit design, the 63-volt capacitors are operating at their limit here (with a margin of only 8 V), especially given the potential for voltage spikes in modern power grids. Yamaha engineers deliberately used the uncommon 71-volt audio-grade rating to ensure a safe margin of safety. The danger of installing 63-volt capacitors: If you install the TDK/EPCOS capacitors mentioned earlier, rated at 63 V, they will operate in a critical mode. At the slightest voltage spike in the outlet (for example, if the mains voltage is 235 V instead of 220 V), the DC voltage on the power rails will rise above 58–60 V. Repair Recommendation: When replacing the original Yamaha B-2 capacitors, it is strongly recommended to choose modern capacitors with a voltage rating of at least 80 V (for example, 22,000 μF / 80 V). This will provide an ideal and safe margin of reliability for the vintage circuit. "
Click to expand...
Based on guidance from Nichicon and other manufacturers, it’s best to run capacitors to near or slightly below their full voltage rating. Instantaneous spikes in line voltage, as long as they’re not extreme, will not cause any damage to the capacitor, after all, a capacitor is not a bomb! Sustained higher voltages will, however, damage the electrolytes and cathode/anode electrodes and insulation film inside, causing loss of capacitance, excessive leakage current or both. It’s worth noting also, that most of electrolytic caps parameters are measured at full rated voltage, not far below.

With all that said, if using an 80V cap is feasible and makes one feel better, by all means, but it’s not a requirement.

Edit: If worried about power surges, consider using a surge protector.
 
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