Yamaha B2 - the "why" and the "how" of a comprehensive rebuild
- Thread starter rottalpha
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- v-fet yamaha b-2
Arye, how are you doing with that B-2? Did you locate spare vfets?
Great, I hope you get her back and running again.
Pete,
Out of curiosity, what brand of capacitors are you using on your driver boards?
They don't look like the regular Panasonic polypropylene units that many people go with.
Out of curiosity, what brand of capacitors are you using on your driver boards?
They don't look like the regular Panasonic polypropylene units that many people go with.
they are wima caps
most are decoupling caps so you can use a variety of choices.
Special attention to be paid when replacing the small value styrene caps. Those are part of RC filters and have to be of good quality. The original are excellent and do not need to be replaced. I usually do not replace them. Th 330pf cap is particularly important.
most are decoupling caps so you can use a variety of choices.
Special attention to be paid when replacing the small value styrene caps. Those are part of RC filters and have to be of good quality. The original are excellent and do not need to be replaced. I usually do not replace them. Th 330pf cap is particularly important.
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Thanks.
If you have them, would you mind dropping some part numbers for the input JFET differential pair that would work with the adapters you provided? I prefer regular packages with legs, no surface mount.
If you have them, would you mind dropping some part numbers for the input JFET differential pair that would work with the adapters you provided? I prefer regular packages with legs, no surface mount.
I am a long legs kind of guy too, but not too many long legs around these days
The SMD is the way to go. You get different ranks choices and they work like a charm.
The TH adapters are for Siliconix and LinearSystems parts. Expensive and difficult to get.
If you insist on TH, then look for LSK389 rank A and 2N5564. Both tested to work well.
If you want easy then go with the SMD Toshiba 2sk2145, something that I found to work equally well or better, but not without some initial headaches due to my own ignorance. Also don't be surprise if you find that you like the BL rank better than the GR or the Y rank. They all work. The Y rank would be a same IDSS as the the original Sony 2SK143s used in all B-2s. The BL would have same IDSS as the 2SK100 used in the B-3
The last candidate is the dual jfet from TI. I have done little work with that and have no opinion at the moment.
zaibatsu
yam
LSK389 will have higher Ciss than the original 2SK43 parts, correct?
I would see 2SK2145 as the better choice (based on dual 2SK209, which are the SMD equivalents of TH 2SK117) - but perhaps it makes no difference - would appreciate your thoughts.
Also any elaboration on the headaches, just pin config woes or something else to be mindful of?
Planning to use some of the adapters you sent soon, haven't decided what to put on them yet.
I am a long legs kind of guy too, but not too many long legs around these days
The SMD is the way to go. You get different ranks choices and they work like a charm.
The TH adapters are for Siliconix and LinearSystems parts. Expensive and difficult to get.
If you insist on TH, then look for LSK389 rank A and 2N5564. Both tested to work well.
If you want easy then go with the SMD Toshiba 2sk2145, something that I found to work equally well or better, but not without some initial headaches due to my own ignorance. Also don't be surprise if you find that you like the BL rank better than the GR or the Y rank. They all work. The Y rank would be a same IDSS as the the original Sony 2SK143s used in all B-2s. The BL would have same IDSS as the 2SK100 used in the B-3
The last candidate is the dual jfet from TI. I have done little work with that and have no opinion at the moment.
Thank you, sir!
SMD, it is. I'm 45 and I'm just now finding it harder to see close-up, so this will be fun.
The TI JFE2140 Works well for the 2SK100 in the Yamaha C4 and A-1 . I wonder if they also would be good in this application, isn't the B3 not that far off in circuit design as the B2?
It has the same or close Idds Drain-to-source saturation current ratio as the 2SK389
Min-Typ-Max
0.95, 1 , 1.05
Athanasios
It has the same or close Idds Drain-to-source saturation current ratio as the 2SK389
Min-Typ-Max
0.95, 1 , 1.05
Athanasios
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Yes, I just have to personally experiment more with the TI jfet
That IDSS is same rank within what is original to B-2 but not to the B-3
Silver mica is about the best cap you can get for that role, but the original styrene caps would have been just as good if they were not damaged, so do not throw them out.
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It is just about that time when I felt the need to get glasses for reading
Yes but this is not a phono stage and it actually works and sounds very good. The LSK489 would have lower input capacitance and works too. Ask me how I know.
But I prefer the SMD.
The headache was due to my ignorance of not allowing air to circulate from underneath the B-2 when I was experimenting with the SMD jfet. This had me running in circles for a couple of weeks because I could not explain why the DC offset was swinging up and down faster than NADAQ.
btw, two transistors face to face work but no better than the original setup and it was not what I was looking for. I wanted a single package dual jfet, preferably single die dual jfet.
zaibatsu
yam
Understood and appreciate the explanation.
It's good to know there is some flexibility in parts choice without affecting function significantly too.
Ultimately in these amps without DC servos it's worth paying attention to this area, not just electrically but with respect to thermal stability and thermal currents too. On that note I have wondered if adding heatshrink over the assembly (whether single or dual) is preferable over / in addition to the metal housing on the stock B-2. However I'm not sure if this poses a dissipation concern on the SMD parts with ~halved Pd values - what do you think?
I do consider the B-3 superior in this aspect with the mirrored driver boards maintaining thermal channel symmetry on the input pairs (compared to the B-2 with one pair off to one side). I suspect there's a reason Yamaha went to all that extra effort (not just for the BTL circuitry). I've wondered if it's something you'd consider if/when the B-2 driver boards get visited. I'd eventually like to put single packages back in the B-3s too, building another currently so I will try the parts you recommend. I agree it's the preferable solution.
Anyway it's nice to have a place to discuss these topics and I appreciate it.
It's good to know there is some flexibility in parts choice without affecting function significantly too.
Ultimately in these amps without DC servos it's worth paying attention to this area, not just electrically but with respect to thermal stability and thermal currents too. On that note I have wondered if adding heatshrink over the assembly (whether single or dual) is preferable over / in addition to the metal housing on the stock B-2. However I'm not sure if this poses a dissipation concern on the SMD parts with ~halved Pd values - what do you think?
I do consider the B-3 superior in this aspect with the mirrored driver boards maintaining thermal channel symmetry on the input pairs (compared to the B-2 with one pair off to one side). I suspect there's a reason Yamaha went to all that extra effort (not just for the BTL circuitry). I've wondered if it's something you'd consider if/when the B-2 driver boards get visited. I'd eventually like to put single packages back in the B-3s too, building another currently so I will try the parts you recommend. I agree it's the preferable solution.
Anyway it's nice to have a place to discuss these topics and I appreciate it.
I have mixed feelings about encasing the transistors. That is the first thing I did actually when I started to experiment. I would be curious what you find out.
My concern is about the added casing preventing the transistor from reaching operating temperature quick enough.
Soon enough I will post a video with adjustment procedures for a B-2. It is what I found working best after countless times of getting aggravated.
Yes, the geometry of the B-2 mechanical design is less effective from this perspective but also preferable from other perspectives. I can't say I prefer one over the other, but when the B-2 amp boards get redone, there will be some tweaks to eliminates some of the current challenges.
Yes, I would say so. either the original if still OK, and most are still OK, or the SMD package. 2SK2145BL is same rank as the original 2SK100.
You bet! Feel free to add to this thread anything you find appropriate about B-2 or B-3 for that matter. Having multiple sources of information centralized in one location is the goal.
Mr. Yamaha
Not so much Yamaha lately...
Awesome thread, Pete! Where was this thread in 2016? 
Makes me want to redo or 'finish' my B-2 resto (which is still playing sweet music every day since it was finished).
Reading this thread gave me enough itch to finally start with the restoration of my TA-N7B, which I did this week. Will be a slow project I guess due to the fact of having two little kids
Keep up the good work! I will follow this thread and may PM you in the foreseeable future about those upgrade boards you developed for the B-2
But first the TA-N7B...
Again, awesome work!
Makes me want to redo or 'finish' my B-2 resto (which is still playing sweet music every day since it was finished).Reading this thread gave me enough itch to finally start with the restoration of my TA-N7B, which I did this week. Will be a slow project I guess due to the fact of having two little kids
Keep up the good work! I will follow this thread and may PM you in the foreseeable future about those upgrade boards you developed for the B-2
But first the TA-N7B...
Again, awesome work!
Yes indeed! I restored may first B-2 back in 2008 when there was little to no support. We've come a long way since then thanks to your love for this amp and your diligent work so far, not to mention your willingness to share it with others in this thread. You've certainly taken B-2 restoration to a whole new level!
