Uncle Paul
Super Member
Mr. Yamaha's B-2 restoration thread has been both informative and inspiring. As a result my first B-2 has been stripped down to the chassis and is undergoing rehabilitation from the ground up. Rather than dogpile on that thread I am starting my own to help keep that thread focused on his restoration effort.
Coming on six years ago I stumbled across a B-2 that had just been listed locally on Craigslist. I set up an appointment to audition it that afternoon and it was love at first listen. Unfortunately, after I drove it home I found that one channel was out. Fearing the worst I went to remove and test the VFETS only to find that one of the connector boards between driver and power FET board had snapped in half. Fortunately the VFETS were undamaged and after I replicated the connector board all was well
Note: My B-2's are far from museum pieces, but they aren't overly rough, either. I'm not trying to do a historical restoration, but rather the goal is reliability, sonics, and above all protect those VFETS! All original parts, however, are being documented and saved if they will be needed for some future reason.
The electrical portion of the rehab starts as always with the B-2's heart - it's power supply. I've made some capacitor changes based on insights from Mr. Yamaha's thread. While I'm waiting on some parts I started work on the Electrolytic Capacitor board and that brought up a couple of points I'd like to get some feedback on.
When I planned some of this rehab a few years ago I made a few decisions that I am rethinking about now. The first involves the main capacitors. At the time I decided to go with Mundorf M-Lytic 2200 uF 63V caps over the more typical Nichicon KG, but today would probably go with the Nichicon KG's and keep it simple.
They have been used in B-2's before
But when I look at them side by side with the original Nichicons it gives me doubts that they are truly electrically equivalent.
My first question is given that I have the Mundorf's in hand is there a compelling reason to sell them and get the Nichicon? I can say that if I had to do it all over again I'd have gotten the Nichicon.
My second concern is that I also bought 30A 600V Fairchild ISL9R3060G2 "Stealth: diodes AKA FREDs to replace the main PS diodes. These aren't expensive and it isn't a huge loss if I decide to stick with the factory diode bridges, but they are more efficient and less noisy, so should be an improvement. I was working on the Electrolytic Capacitor board this afternoon and decided to try to see how best to mount the FREDs and finally came up with the following:
This is just a test fit and function check even though they are soldered in. The complicating factor is that the anode of the FRED on the left does not go to a solder pad, it's just a convenient hole in the PCB that was there to accommodate the frame of the original Toshiba bridge, and there is no pad to solder to. It turns out that the cathode is enough to provide solid enough support. The question here again is that is there a compelling reason to stick with the original bridges over the FREDs?
In any event, they and the remaining bridges are coming out to accommodate a proper cleaning since Mr. Yamaha has raised the standard for PCB cosmetics. Just make sure when you go to remove the filter caps from this board to have plenty of braid on hand:
Coming on six years ago I stumbled across a B-2 that had just been listed locally on Craigslist. I set up an appointment to audition it that afternoon and it was love at first listen. Unfortunately, after I drove it home I found that one channel was out. Fearing the worst I went to remove and test the VFETS only to find that one of the connector boards between driver and power FET board had snapped in half. Fortunately the VFETS were undamaged and after I replicated the connector board all was well
Note: My B-2's are far from museum pieces, but they aren't overly rough, either. I'm not trying to do a historical restoration, but rather the goal is reliability, sonics, and above all protect those VFETS! All original parts, however, are being documented and saved if they will be needed for some future reason.
The electrical portion of the rehab starts as always with the B-2's heart - it's power supply. I've made some capacitor changes based on insights from Mr. Yamaha's thread. While I'm waiting on some parts I started work on the Electrolytic Capacitor board and that brought up a couple of points I'd like to get some feedback on.
When I planned some of this rehab a few years ago I made a few decisions that I am rethinking about now. The first involves the main capacitors. At the time I decided to go with Mundorf M-Lytic 2200 uF 63V caps over the more typical Nichicon KG, but today would probably go with the Nichicon KG's and keep it simple.
They have been used in B-2's before
But when I look at them side by side with the original Nichicons it gives me doubts that they are truly electrically equivalent.
My first question is given that I have the Mundorf's in hand is there a compelling reason to sell them and get the Nichicon? I can say that if I had to do it all over again I'd have gotten the Nichicon.
My second concern is that I also bought 30A 600V Fairchild ISL9R3060G2 "Stealth: diodes AKA FREDs to replace the main PS diodes. These aren't expensive and it isn't a huge loss if I decide to stick with the factory diode bridges, but they are more efficient and less noisy, so should be an improvement. I was working on the Electrolytic Capacitor board this afternoon and decided to try to see how best to mount the FREDs and finally came up with the following:
This is just a test fit and function check even though they are soldered in. The complicating factor is that the anode of the FRED on the left does not go to a solder pad, it's just a convenient hole in the PCB that was there to accommodate the frame of the original Toshiba bridge, and there is no pad to solder to. It turns out that the cathode is enough to provide solid enough support. The question here again is that is there a compelling reason to stick with the original bridges over the FREDs?
In any event, they and the remaining bridges are coming out to accommodate a proper cleaning since Mr. Yamaha has raised the standard for PCB cosmetics. Just make sure when you go to remove the filter caps from this board to have plenty of braid on hand:
Last edited: