Yamaha B-1 restoration/repair

[Vint Age]

I have spares kits, yes !

I have no spare kits at the moment ...

 

[Vint Age]

About the MX-10000. It has 'balls' and stamps its authority, can also be delicate,

This is also how I would describe my B-1.

 

[vintagejapan]

This is also how I would describe my B-1.

Only that the lower bars on bass are more detailed and better controlled on the MX-10000.
And mine is still all original, I only did a simple clean and adjusted the bias and DC balance sometime ago.

I do have the internal pics somewhere, the build quality is outstanding- but I guess that can make another thread

 

[vintagejapan]

I discovered that a curve tracer is a VERY good thing to have as such, and especially with VFETs.
So, mostly adjusting the bias and balance circuit values to reach the required bias voltages, I suppose.

Yes, the B1 is a unique amp in many ways - topologically, there is nothing similar to it out there, ditto general construction. It was after all a true 'statement amp' right down to semiconductors developed only for use in it. I'd certainly like more of them to work than to turn into parts units.
Once up on a time when Sony 2SK82 were still available, I suppose two in parallel could have been used instead of a single 2SK77, though that requires making a mechanical 'adapter' for the heatsink...

What are your experiences with 2SK75 failing? This is really not easy to replace, especially as Yamaha saw fit to use 3 different 'ranks' in the B1...

The 2SK75's are also a issue, one suggestion would be to keep the couple on the filter circuit as spares and run the amp only with the "direct in" option
Even if the filter circuit ones are only "C" rank, I have seen it done before. My first B-1 had a dead 2SK75 on one of the driver circuits but luckily I did come across someone selling only the B-1 driver boards as spares.

The amp fitted with the 2SK180's is running perfectly all this time, and also run slightly cooler than when fitted with the 2SK77's

 

[jbert]

Nick, in our correspondence you mentioned that resistor value changes on the driver board were needed when using 2SK180's to replace 2SK77's which are lower Mu devices. Would you mind sharing that information in this thread?

I have been reading your B1 upgrade with interest. I bought some used 2SK77's on eBay a while back to try to repair my old B1 that died back in 88. Pretty sure all it needs is 2 output devices (I have 4). I've checked all the power supplies per b1 service manual and they are good. So now I am at the driver section. I don't have signal generator or distortion meter and don't really feel all that comfortable going further. Do you know anyone around Texas/Okla area who works on these. Or would you consider doing it?

 

[Mark B]

I have been reading your B1 upgrade with interest. I bought some used 2SK77's on eBay a while back to try to repair my old B1 that died back in 88. Pretty sure all it needs is 2 output devices (I have 4). I've checked all the power supplies per b1 service manual and they are good. So now I am at the driver section. I don't have signal generator or distortion meter and don't really feel all that comfortable going further. Do you know anyone around Texas/Okla area who works on these. Or would you consider doing it?

I recommend contacting Vint Age.

 

[Vint Age]

I recommend contacting Vint Age.

Thanks Mark!

I have been reading your B1 upgrade with interest. I bought some used 2SK77's on eBay a while back to try to repair my old B1 that died back in 88. Pretty sure all it needs is 2 output devices (I have 4). I've checked all the power supplies per b1 service manual and they are good. So now I am at the driver section. I don't have signal generator or distortion meter and don't really feel all that comfortable going further. Do you know anyone around Texas/Okla area who works on these. Or would you consider doing it?

Check and you'll see I sent you a PM.

Mark had 2 dead B-1's that he sent to me with the goal to make 1 working 1 out of the 2 since there was only 1 set of working K77's. With some time I was able to put together 1 very nicely working B-1 for him which I enjoyed doing and I hope he's still enjoying listening to now. He also had me replace the main dual caps to help make it live well into the future. As partial compensation for my effort he very generously gave me the left over pieces to use as a platform for repairing other B-1 boards.

 

[Vint Age]

My bench right now thanks to Mark and another B-1 AK'er.

 

[jbert]

My bench right now thanks to Mark and another B-1 AK'er.

 

[jbert]

I checked the caps and they are good. I'm now at the driver section. Not sure if I should continue or send driver boards + 4 2SK77 modules out to be fixed. I have 4 2SK77's but not test equipment. Also I don't fix audio equipment (I work on MRI). What do you think?

 

[Vint Age]

I checked the caps and they are good. I'm now at the driver section. Not sure if I should continue or send driver boards + 4 2SK77 modules out to be fixed. I have 4 2SK77's but not test equipment. Also I don't fix audio equipment (I work on MRI). What do you think?

I think you should log in and check your inbox.

 

[Vint Age]

My bench right now thanks to Mark and another B-1 AK'er.

This should have said, these are on my bench right now for repair from another AK'er thanks to my having Mark B's B-1 donor chassis.

 

[rottalpha]

This should have said, these are on my bench right now for repair from another AK'er thanks to my having Mark B's B-1 donor chassis.

Hi Vint Age, have you ever re-order another set of boards for the main caps mod?

 

[Vint Age]

Hi Vint Age, have you ever re-order another set of boards for the main caps mod?

Hi rottalpha - Congrats on your recent C-1 UC-1/B-1 score! Mark B. commented to me after he received his B-1 back that he felt it sonically rivaled his MX-10000 so get ready for a real listening treat.

No I haven't ordered anymore just yet but I'm working out the deal details on getting another limping B-1 on my bench for restoration/reconditioning and if that happens I'll be looking at ordering a few more since I need one for my donor B-1.

 

[Mark B]

Hi rottalpha - Congrats on your recent C-1 UC-1/B-1 score! Mark B. commented to me after he received his B-1 back that he felt it sonically rivaled his MX-10000 so get ready for a real listening treat.

No I haven't ordered anymore just yet but I'm working out the deal details on getting another limping B-1 on my bench for restoration/reconditioning and if that happens I'll be looking at ordering a few more since I need one for my donor B-1.

Count me in for 2 boards if you do a group buy.

 

[rottalpha]

Hi rottalpha - Congrats on your recent C-1 UC-1/B-1 score! Mark B. commented to me after he received his B-1 back that he felt it sonically rivaled his MX-10000 so get ready for a real listening treat.

No I haven't ordered anymore just yet but I'm working out the deal details on getting another limping B-1 on my bench for restoration/reconditioning and if that happens I'll be looking at ordering a few more since I need one for my donor B-1.

Thanks, I really wanted one. If it makes a difference to make the deal happen, count me in for two boards. I will keep one as spare, you never know. If it does not make a difference and you have enough for a group buy, then one board is enough.

Cheers,

Pete

 

[Mark B]

Resurrecting this thread. Nick, when might you be ordering more of the filter cap boards?

 

[Vint Age]

Resurrecting this thread.

Mark, thank you for your offer and your interest. Fall is coming and with it my B-1 will be moving back to front and centre for the cooler months. I was considering coming up with a new version that used multiple paralleled caps but maybe I'll just stick with what I know works and order a few more in the fall since the donor B-1 with the K180 outputs deserves the upgrade ...

 

[Mark B]

Nick, can I preorder a couple of the boards for the filter cap mod? They would make nice stocking stuffers for Christmas.

 

[Vint Age]

Nick, can I preorder a couple of the boards for the filter cap mod? They would make nice stocking stuffers for Christmas.

LOL ... I've been procrastinating on ordering more blank boards because of my other project on the bench right now. I don't think I'll have any ready in time for Santa this year ...