B-2 for spare parts NOT V-Fets

clinic-audio said:

yes, I do ;

I have also some YAMAHA B2 needed service , they are not in perfect condition but every damaged part is rebuilt or cleaned when it is rusty

see my chassis pictures !

Click to expand...

All I can say is..woooowwww. Now let me pick up my jaw off the floor.

What is the process called to get the metal back to that state..I was considering plating the chassis of some old amps, but this is amazing.:thmbsp::thmbsp:

Patrice, all I can say is that I wish you lived closer....

OK, so I opened the amp today and swapped the vu-meter wires.
It is official. The right meter, the one with the bent needle which was not working previously, does not work when connected in place of the working, left vu-meter. Additionally, the working left vu-meter connected to the right channel works but it sometimes moves erratically. So I would need to repair the right channel of the meter board as well.

I took a couple of interior photos. The v-fets in this amp are 2SK76A and 2SJ26A. I did not see much non-original work being done inside. All I noted is a bunch of dust.

The 4 volume knobs are not original.

I have been running the amp for a little longer this time and I have to say that it sounds very good. I can only imagine how it will sound once it is fully re-caped.

I have attached some photos. The needle of the non-working right channel vu-meter is really bent.

So as of now, I am hunting for a working vu-meter and possibly a working meter board (so I won't have to mess with mine). Additionally. I would need 4 original volume knobs. I believe that I can make the rear plate and connectors look good once I clean it and install all new speaker and input connectors.

Hello !

What is the process called to get the metal back to that state..

chemical bath :thmbsp:

To rottalpha

I honestly don't know where we can find a working B2 meter ...:scratch2:

clinic-audio said:

Hello !

What is the process called to get the metal back to that state..

chemical bath :thmbsp:

Click to expand...

@clinic-audio

WOW those are beautiful!

Any specifics? Did you do it yourself or did you have it done by a specialist? What preparation did you do, do you know the name of the process?

Inquiring minds want to know...

clinic-audio said:

To rottalpha

I honestly don't know where we can find a working B2 meter ...:scratch2:

Click to expand...

WOOW..stop rubbing it in and send me one already..before I die of envy..
Hell, I'll take two since you got 'em in pairs.

Hi Patrice, plz check your box, PM sent.

Replacement meter in da house

Meter and misc parts arrived

ilimzn is a true gentleman. My B-2 will be saved...

Thank you Mr Z!

tear-down for full rebuild next

I love a happy ending:thmbsp:
One day i will have to restore my B-1

Hello

One day i will have to restore my B-1

Why not if we can help you !

clinic-audio said:

I forget to add the picture of my 4 VFET mounted on B2 heatsink last week
(they are new of course)
here is the last picture of a renewed B2 chassis :thmbsp:

Click to expand...

Are you sure K98/J38 will work? They are VERY different from J27/K76, for one thing the D-S breakdown voltage is around 100V (although specified much lower) even though most VFETs are far underspecified in this regard, this is below the at least 120-130V needed for a B2. Or, are they mis-marked (I've seen that too).
If needs must, it is possible to fix a B2 using Sony J28/K82, though some small modification would come in great (also would work for the original J26/K76)

vonclod said:

I love a happy ending:thmbsp:
One day i will have to restore my B-1

Click to expand...

and one day I will hope to have a B-1

OK, so I have a few questions..

Looking at the spare boards I have here and reading through the trends, I see a consensus about the 2SC458 trannies that need to be replaced.

How about the rest of the trannies on the PSU and meter board. I mentioned these two boards because I have the spares from Z on my bench...the question applied to the rest of the boards as well...

Which other semiconductors are problematic / prone to fail? Which other trannies should be replaced and what are the equivalents?

Besides the 2SC458's on the meter board and PSU board I have the following:

Meter Board
2SC1345
2SA841
2SA561
2SC734

2SC1061
2SA671


PSU board

2SC1439B
2SA858V
2SC1166
2SA841
2SC734

2SC789
2SC1448A
2SA740A


I am planing to replace all electrolytics, D205,206 30v zeners and the relays;
I will replace the trimmers on the amp boards with Bourns, but how about the meter board...is that overkill?

Some folks mentioned replacing some of the carbon resistors with metal resistors. I assume this would be good practice in order to minimize variations associated with carbon resistors response to variations in temperature. Are there any particular resistors that should be replaced / upgraded to metal?
I should say, which would be the circuit areas that would most benefit from the change of carbon resistors to metal resistors?

I was hoping that someone familiar with B-2 would chime in before I place the parts order...it sucks having to place multiple orders.

Maybe this attachment helps
It shows replacements for the original transistors on the driver boards, this configuration has been tried and tested and works. BE CAREFUL with pinouts!!! especially with 2N5401/5551. Replacements for the drivers are specced as giant TO92 case transistors. It is possible to remove the aluminium rings from the originals and push them onto the replacement plactic ones (file off the excess plastic left from moulding and apply a drop of silicone greese), then the original star heatsinks can be fitted too.
Also, do not bother with carbon film resistors, your semis have 100-fold variations for nearly any reason you care to name. What does need change are ALL fusible resistors, all fusible and power resistors. You need 4x47 ohm, 2x390 ohm 0.5 or 0.6W metal film to replace the small fusibles (there are two 47 ohm standard carbon resistors in a sleeve, just remove it and solder them normally. Also, you need 2x22ohm/2W, 1.2k/2W, 2x1k/2W. Modern ones are much smaller cause they can operate at higher temperatures. Fusibles were used as non-flammable resistors or flame retardant, today's metal film are all non-flammable (whereas carbon film can flame due to carbon being combustible). Dual junction diodes are the next candidates (use 2x1N4148 in series), also all of the green polyester caps. You can change them with the same material caps but non-inductive (which is what the originals are not). Classic Wima, AVX etc will do. Today most are smaller size for the same spec.

The aux power and protect board and meter board can use lots of modern replacement transistors. For instance, if you keep the TO220 series regulator transistors, most except of the relay driver transistor can be replaced with generic 60V/100mA parts on the meter driver (pinout!), except in the regulator section where 100V/100mA parts should be used. Most on the aux power/protection board can be replaced with 2N5401/5551 (again, pinouts!). There is nothing overly special in the selection of the original parts there. The relay driver would ideally be a slightly more powerfull part, 50V/200mA.

All the boards have triangular transsitor pinouts for everything but the TO220 series regulator transistors, so it is possible to fit almost any pinout with a bit of care. Te series regulator transistors on the aux power board could benefit from better heatsinks, the slight problem being how to fix them (or indeed the original ones). The original glue method leaves a LOT to be desired...

Thank you!

clinic-audio said:

Hello

One day i will have to restore my B-1

Why not if we can help you !

Click to expand...

I was talking about the B1 with some other audio buddys and subject of unavailability of the important bits came up..I mentioned there is a guy in France who seems to have the goods and willing to help:thmbsp:
This will be my 1st stop when I decide to dig in.:thmbsp: as for now it sounds great and has been checked over/biased before I ran it for the 1st time, I do keep it cool when I do run it.
Thanks

rottalpha said:

and one day I will hope to have a B-1

Click to expand...

I was lucky to be in the right place at the right time and in front of the lineup
I think you're doing pretty good so far:thmbsp:, you have your foot in the VFET door..good luck with your B-2

Thank you!

I can't wait to have this B-2 all sorted out..It will take a while, but it will eventually happen.

Oh yes - one VERY important thing:
When working on the B2 driver board, or indeed the whole channel, be ABSOLUTELY sure to follow the service manual procedure and discharge the main filter caps. Failing to do so may cost you the VFETs. This is particulairly important when removing the driver board, check that the main power is near zero V (easy to measure on the solder lugs of the VFET board). There is also a way to power up the driver board alone so you can check that everything works properly before the VFETs are installed. Any problem with the driver board that results in the VFETs not being biassed properly at power up can kill them in an instant. This procedure makes it possible to check the basic functionality of the driver board, including bias and offset nulling.