Jump to content

vintagejapan

Yamaha B-1 Vfet monster, restoration

Recommended Posts

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

 

 

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites


Fantastic restoration underway.

Shanks for sharing this job so far .

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Grizzly
      Just picked up something very special....shhhhh




    • By coppinger
      Is there anyone on SNA who has built or is contemplating a build of the Nelson Pass VFet amplifier project.( the one with the Sony VFets) ?
      Apologies if I have missed any posts/threads in this regard.
    • By hififormusic
      After some don't know how many years, 10?20?30?...what a feeling!

    • By The Fez
      Sony TA-N7B
      1977 160,000 yen 100w + 100w 8ohms 21kg Two independent monaural amplifiers Harmonic distortion .01% First stage – voltage amplifier. Dual FET input, a differential cascode amplifier, current mirror output circuit at the first stage and a bipolar transistor cascode amplifier at the next stage.
       
      Drive stage – Fully complimentary push-pull power amp.  – Sony V-FETs 2SJ18 & 2SK60 plus bipolar transistors in cascode configuration. Triple dual output configuration per channel.
       

       
      The TA-N7B is considered a statement product from Sony. Just looking at the rather small footprint of the N7B tells you it’s built extremely well. Designed and built up to a standard, a standard in the late 1970’s that was very high.
       
      Sony’s aim in designing and building the N7B was to produce a state of the art audio amplifier employing the very latest and best audio engineering possible at that time.
       
      Some 37 years later, those experienced with this amplifier and technically qualified may look now and see the flaws in the designs. I’m no audio engineer; I don’t claim to be of any technical expertise. But I do like listening to music, and this amplifier was no doubt built to reproduce music to the highest fidelity level possible.
       
      Aesthetics, design, look? – It’s a matter of taste. I’ve had someone tell me the amp looks like a dorm refrigerator they had in college!  – joking?, perhaps. When in the listening position and looking at the face, it is a very nice simple design. The backside, aint that flash in my opinion. It is unique that is the fact.
       

       
      Restoration  
       
      The amplifier has undergone an extensive rebuild. Over 180 parts have been replaced.
       
      Also, some discrete enhancements or modifications have been done to make the amplifier more stable and to sonically take it “up†to another level. The alterations were researched, tested, re-tested, applied, then re-tested, to exacting standards (as the N7B demands) to ensure the highest level of integrity, and sonic purity.
       
      All replacements parts and substitues used are absolutely appropriate and precisely matched wherever required across all circuits.
       

       
      Listening to the Sony TA-N7B
       
      Plugged in and allowed to idle along at low volumes for a good hour before putting the foot down. It’s a bit like having a classic car restored, and you’re taking it out for a drive. You know it’s good, you know it’s been restored very well, but you just want to treat her gently.
       
      Once warmed up the Sony delivers a beautifully balanced sound, with what I describe as -- elegant power.
       
      A stupendously articulate and detailed delivery. Tonally, very refined and nuanced, nothing but the music is heard, in front of a completely silent background. But it is not cold or clinical. You will hear instruments and detail never heard before. You will hear a wavering in a voice or a backing singer, you never heard before. The layering and purity of the sound is quite amazing.
       
      Source and recording quality is therefore an even more important element when running the N7B. Critical of source is the TA-N7B no question. Transient speed and dynamics are wonderful. It’s a “quick†amplifier this Sony, very quick.
       
      Bass / low frequency is also superb. Mid bass, upper bass, low bass it’s all in there. The amplifier goes so low and with wonderful definition and control. Midrange and highs are also excellent. In particular vocals and piano is where the Sony excels. Voices and instruments seem to leap into the room with you.
       
      The only “weaker†aspect perhaps is the stereo separation. Not as good as expected or doesn’t seem to be in the same class as the other aspects of the amplifier. It’s very good, but not exceptional. Certainly the Sony ESPRIT TA-N902 (the best soundstage I’ve heard in an amp) & the Yamaha B2 seem to have better sound staging and separation
       

       
      Speaker choices need to be considered. You want an excellent full range speaker that has excellent grip and control on the bass, images really well. I have developed an immediate case of – floorstandis speaker-upgradeitis. Speaker placement as always is critical. Set up precisely to get the best from the Sony.
       
      Put a decent preamplifier with the N7B, one with reasonably high outputs. The N7B, as a result of the wonderful design, and sonics is a low gain amplifier. But that’s just the way it is.
       
      A beautiful highly accurate, linear, low noise (no noise!) and dynamic amplifier. You’ll really enjoy listening to your music with the Sony.
       

       
      Equipment
      Sony TA-N7B Stereo Power Amplifier Emotiva XSP-1 Balanced Differential Preamplifier Squeezebox Touch (EDO) Audio-dg NFB1.32 ES9018 Sabre DAC Krix Apex Floorstanding Speakers – 4ohms Quad 12L2 Standmount Speakers – 6ohms Grave Science interconnects  Music
      Eagles -  Hotel California – 192khz Rick Braun – Sessions II Tim Finn, Bic Runga, Dave Dobbyn – Together In Concert Steely Dan – Gaucho – 96khz Supertramp – Crisis What Crisis? Il Sogno – Elvis Costello Amy Winehouse – Frank  
       
       
       
×