Discussion in 'Yamaha' started by vintagejapan, Feb 18, 2018.
The white caps are CDE and replaced the Yamaha Mylar 1uf. This was the board beforehand
This thread is pure gold for me as I intend to do the same treatment to my B-3 this summer... As far as I know, this is the first documented thread about Yamaha B-3 restoration.
I want to be sure that I get all the correct info, so I have some questions:
- how did the big power supply caps capacitors (27000 microF/63V) perform on measurements?
- transistors TR301,304,306 are 2SC1175 or 2SC1775? It appears to be 2SC1175 from the pictures.
- capacitor C310 is what? I cannot see from the schematics...
- the relay from the Muting board NA 06961 is replaced by?
P.S.: I was not able to find a second B-3 here in China. They were sold like hot cakes...
Very nice indeed and thank you! Sadly this is likely the closest I'll ever get to one so I hope you keep it coming; from here it looks like another very fine piece of Yamaha V-FET sonics well worth the TLC.
I too have some questions:
- Could you share your source and part number for the two relays?
- Any chance you could share the regulator board schematic (+/-85V regulated supplies)?
- Will 66x105mm fit for the main capacitors, or 63mm max?
- Are you going to replace the driver transistors?
For the drivers, a hFE of 130-330 is called for, may be tricky to match with currently available parts in sufficiently low Cob.
It would be interesting to hear if your amp uses drivers from the Q or R gain group (should be written on them).
Thanks in advance!
Thank you for the info, those caps fit nicely.
B-2 taps out at ~150W so the B-3 is about 1/2 as powerful as a B-2, which does make sense given that it uses 1/2 of the outputs.
Which ones? I can see if mine have more legible writing.
will you do it? what happened with the tech you were going to take the amp to?
These are not made in China so why look for them there?...hint: they come for sale often where they were made
si nu crezi ca eu stiam deja asta?
Funny thing, I put the B-3 in the car, visited some relatives on the way to the tech and then winter has arrived in Romania, with very big snow. I was reluctant to drive in such conditions (ice on the road), and postponed the operation. Now is a clean road, but I'm in China....Talked to my tech to begin in the summer though.
Apparently the Chinese recognize the good quality audio, they have some goodies on their market that you couldn't believe it. Thanks for the relay info, rottalpha!
I am sure they do, but the real goodies come from other countries...so why not search directly there??
Should the double diodes on this amp be replaced, and/or any other diodes?
There's some VD1212 on both regulator and power amp boards.
Given the importance of the regulated +/-85V supply, I feel it would be wise to replace the regulators - my best idea for 2SC1624 (O,Y) --> MJE15034. Is there a better option than this? Most specs are better, only thing that might be lower is gain - but this is the best from the MJE150xx family for that.
It would be good to discuss what needs to be replaced (and what to replace it with) as part of a full rebuild - would help others in future too.
I wonder where @vintagejapan went.
I agree, I know in some areas of audio they are pursuing original developments (after already replicating innovations from elsewhere in the world over previous years) and they have now surpassed the level of what they were once just attempting to replicate. In-ear monitors are definitely one area, where brands like DUNU and V-Sonic are considered world class. The future will be interesting for those with open minds!
MJE15034 is a very decent sub; but perhaps a bit overkill with 350V/5A/30Mhz
Therefore more expensive.... and not using its performance.
For this series voltage regulator, a more relaxed transistor like the KSC2073 will do fine (150V/1.5A/4Mhz)
And is at half the price of the MJE15034
Stock part is 30MHz (same as MJE15034), many B-3 seem to have the 2SC1624-Y installed (hFE 120-240)
Just checked KSC2073 from recent mouser purchase, hFE = 85, very close to the minimum factory spec (70)
Even the higher H2 grade of KSC2073 has a minimum of 60 (60-125).
I feel the MJE is a better choice here for 80c extra.
I'm sure both will work fine, good to have options.
I concur when looking for like-for-like. Those 2SC1624 were really good transistors, notably at that time, and funny enough no direct sub in production today, unless uprating some parameters like the Vce of mentioned MJE (which will provide only higher lifespan)
I would definitely take the MJE if it were a simple series regulator configuration, but in this case the regulators are actually configured as a Darlington pair with TR202/208, and as such the 'gain' (i.e. the reactive sensitivity to incoming ripple and noise) is multiplied many times, making the actual Hfe of TR203/207 less important. That's why I mentioned that the KSC2073 would be a (more than) suitable sub.
This just for your information, for when you run into other amps' more simplistic power supply regulators.
No issue to spend a bit more money
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