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Yamaha B-1 Vfet monster, restoration

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Well here it is, a 240v version of Yamaha B-1 Vfet amplifier. I am very lucky to have in my hand this extremely rare monster including the UC-1 meter accessory that allows 5 speakers to be connected and controlled from the front panel. 

 

The Yamaha B-1 is truly one of the best amplifiers Yamaha has made, running a all Vfet circuit and managing to squeeze out 160watt from a pair of giant 2SK77's on each channel. 

Here are the specs. Not bad for the 70's 

IMG_9631.thumb.JPG.73d88dbd8bdf6472dc7f4d02295b5c4a.JPG

 

 

 

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All the boards, and the 4 SK77 each with their own heatsink511328650_IMG_65362.thumb.JPG.4fc0616cd4f826069de155ab196bb253.JPG

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Initial testing is a success, all the jewels are alive and well. 

The parts are ordered and while waiting for delivery will be installing a brand new filtering caps kit.

The filtering caps are enclosed in between the two power transformers which makes replacement not a easy task. 

I have done a kit myself in the past but today installing something special..IMG_2200.thumb.JPG.21c8bbcb69afbfa87e2fb64b74d7e15b.JPG

362031242_NewFilteringcapskit.thumb.JPG.bbea955170850cb76ee908c343de3dbc.JPG

New kitIMG_2183.thumb.JPG.e77799aa1b4eefc37fe385b6f37d1de5.JPG

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the condition of the Yamaha B-1 is very good. Here is the bottom of the amplifier with the old filtering caps still thereIMG_7929.thumb.JPG.02a5d5410b4d218b04349c16e70b20c8.JPG

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With the new filtering caps in is time to check the boards 1 and 2 of the power supply. The operation of this 2 boards and the board 3 of the power supply is crucial for the B-1. 

Powering up the boards 1 and 2 reveals already some issues. The 40v and -200 show up fine, the 12V and -25 also ok, but the +25v on board 1 shows as 40V!!

That will explain why the meters were not operating properly.  

991007778_Testingnewfilteringcaps.thumb.JPG.ed6bbf2d82203f74137f7afc5bf4a8f1.JPG1782324330_TestingPSBoard1.thumb.JPG.ff2774d6369f66eb34c94beea8c8c825.JPGIMG_9202.thumb.JPG.912037c7f3689bb042d6302364f14ea8.JPGIMG_0084.thumb.JPG.34f1f550a5144a175baf9a8cf43ef206.JPGIMG_6073.thumb.JPG.579d1b0f083ee73acad529a43d55e6a8.JPGIMG_5913.thumb.JPG.2a0219ff9fb59d477549b25217373294.JPG

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Fantastic restoration underway.

Shanks for sharing this job so far .

 

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Thanks for sharing. I was very happy for the owner when I read that all 500 vfets are ok. 

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Lovely work, and that filter capacitor conversion board is just fantastic!

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What does the arrow that seems to be pointing to 4 resistors indicate? Just the heat discolouration?

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8 minutes ago, Grizzly said:

What does the arrow that seems to be pointing to 4 resistors indicate? Just the heat discolouration?

 

It might be pointing out the lovely 'off-the-shoulder' number that that poor little capacitor is wearing. 

 

Judging from the following photo, she has a few friends who are similarly attired... along with one whose... erm... arse has fallen out ;) 

 

 

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Posted (edited)

 

1 hour ago, Grizzly said:

What does the arrow that seems to be pointing to 4 resistors indicate? Just the heat discolouration?

Like @pete_mac  I’m guessing but he’s pointing to the cap!  With the other pics you can see how they have expanded passed where the plastic label should be.   Those resistors I assumed they are either wire wound or metal oxide more towards wirewound due to the ends, and will take some punishment as you can see the browning  that’s occured with the Pcb.  There values should be what’s  printed but you never know judging the condition on the pcb, well worth a check and make sure! 

Edited by Addicted to music

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Ah yes, those caps have obviously been a little heavy on the beers and carbs!!

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1 hour ago, Grizzly said:

What does the arrow that seems to be pointing to 4 resistors indicate? Just the heat discolouration?

The arrow points to the cap on top of the 4 resistors(was just scribbling with my finger) which really gets grilled. The thing was almost falling apart...

I will be installing it on the other side of the board and raise those resistors.

 

The first 3 resistors are 2 watts, a, thinking to install 3 watts resistors in there maybe they will not get as hot.

Then a faulty transistor on the first board.

 

Still waiting for the parts to arrive to keep going.

 

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10 minutes ago, Grizzly said:

Ah yes, those caps have obviously been a little heavy on the beers and carbs!!

The B-1 gets toasty hot. I run mine always with a low noise fan on top of this boards, you can get a low noise computer fan and I run it with a lower voltage and you cannot hear it at all. 

 

IMG_4350.JPG.9efcb3185fbf4b1c2218e810d2e64966.JPG

 

 

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If your gonna replace those resistors I’d be tempting to go a 5W   But that will depend on the realestate and the size used.

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OK, I've seen the 10 by 12 glossy nudie photos and we all  know @Grizzly is a stand-up guy who doesn't tell fibs (except maybe to Mrs Grizzly re the cost of hifi purchases and we all do that don't we?).

 

But a 240V Yamaha B1 plus the optional control panel sitting unused and unloved in little old Adelaide?!  How could this happen?  to unearth this legendary monster is the cleverest bit of tracking down great and rare hifi exotica that I've ever come across locally.

 

I think I'll only truly 100% believe when it's safely back in the Adelaide Hills all restored, healthy and pristine.  Then, after seeing touching, smelling and hearing it, I might be able to accept that it isn't all some bizarre fantasy.

 

Please work your magic quickly, Mr @vintagejapan  That beast is needed and wanted at chez Grizzly and it would love to come home ASAP.  Hopefully, Grizzly will allow it to venture out for the odd day trip to the homes of local enthusiasts who would love to hear a comparison between this monster and our more mundane and pedestrian amplification options.

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6 hours ago, Tony M said:

OK, I've seen the 10 by 12 glossy nudie photos and we all  know @Grizzly is a stand-up guy who doesn't tell fibs (except maybe to Mrs Grizzly re the cost of hifi purchases and we all do that don't we?).

 

But a 240V Yamaha B1 plus the optional control panel sitting unused and unloved in little old Adelaide?!  How could this happen?  to unearth this legendary monster is the cleverest bit of tracking down great and rare hifi exotica that I've ever come across locally.

 

I think I'll only truly 100% believe when it's safely back in the Adelaide Hills all restored, healthy and pristine.  Then, after seeing touching, smelling and hearing it, I might be able to accept that it isn't all some bizarre fantasy.

 

Please work your magic quickly, Mr @vintagejapan  That beast is needed and wanted at chez Grizzly and it would love to come home ASAP.  Hopefully, Grizzly will allow it to venture out for the odd day trip to the homes of local enthusiasts who would love to hear a comparison between this monster and our more mundane and pedestrian amplification options.

That is absolutely right Tony!

I was stoked myself to see it in the flesh!

 

Will update the thread as I go, hopefully not long now!!

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Using KA series Nichicon for audio on the B-1, as it gets pretty toasty. 

Parts1.jpg.27257111e472294419404e65b2e21015.jpg

 

 

Parts2.jpg.421c79e2e9e34c4e5da5819420697e58.jpg

 

 

 

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On ‎12‎/‎08‎/‎2018 at 12:25 PM, Addicted to music said:

If your gonna replace those resistors I’d be tempting to go a 5W   But that will depend on the realestate and the size used.

IME even 5W resistors will get just as hot as they will be dissipating the same energy.  The only thing is they are more likely to dissipate the heat over a larger surface area of the resistor body due to increased size and hopefully more heat will be lost this way rather than traveling down the leads to the PCB pad where solder pad and track delamination is probably taking place.
I usually stand the resistor body clear of the board to allow air circulation and place small ceramic sleeve insulators over the leads.  As long as lead length isn't an issue a strain relief loop on each lead also helps get rid of some heat before it makes it to the solder pad.  Just some food for thought.

 

Also the nearby electrolytic should be changed to one with a 105 deg. rating to extend its life and prevent premature failure.  From the look of it in the photo its already suffered considerable heat stress.  :(  From my experience and exploded electrolytic leaves an awful mess inside a piece of gear.  :(

 

Cheers,

Alan R.

 

BTW. Nice restoration. :) 👍

 

 

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Looking forward to seeing your work as always Alex 

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