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B2

B2 external fan install

It seems like a permanent install, I would be more inclined to mount a fan inside, just for the aesthetics value.

I think it would be safe to say, that you like me wouldn’t do any permanent changes that would interfere with the original build.

Actually the B2’s cabinet coating doesn’t really lend itself to the adherence of tape long term and that coating is a bit of a one off, like it or hate it!

And I wouldn’t run my B2 in heat wave conditions for any length of time ,but that’s only me.
 
brinsmead said:
I think it would be safe to say, that you like me wouldn’t do any permanent changes that would interfere with the original build.
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You're absolutely right about that.

Actually the B2’s cabinet coating doesn’t really lend itself to the adherence of tape long term and that coating is a bit of a one off, like it or hate it.

And I wouldn’t run my B2 in heat wave conditions for any length of time ,but that’s only me.
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I prefer to run without fans except on those really hot summer days and for those I use a laptop cooling plate that has 2 very quiet fans housed in a plastic case that I place over the louvers. It comes complete with a power switch and a 12V power pod and stands up on end next to the B-2 when not in use. :thmbsp:

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FETs do not care about heat. In other words, there is no risk of thermal run away like traditional transistors.
My B1 runs about an hour and a half before it gets warm! Yamaha did a good job isolating heat sensitive parts from the heat sinks.
 
Nakdoc said:
In other words, there is no risk of thermal run away like traditional transistors.
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True but since the V-FET's run relatively hot in the first place, there are lots of other components in the B-2 that can benefit from some additional cooling on those hot summer days. A heat related component failure in the power supply or in the protection circuitry or on the drive boards, all of which use BJT's, could still result in some serious damage; I want these old beauties to last well into the future. :thmbsp:
 
B2 VFets

I've never really studied the case size in any detail but the “A” version of the 2SK76A is 2-3mm higher top than the earlier version of the 2SK76A.
These are from s/n 09484 ……purchased new 1979

Earlier “A” versions of both 2SJ26A and 2SK76A had both the same build height.
I wonder what serial number's things changed ?
 
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Its a great study Vintage, the VFets are indeed an very interesting subject.To the casual observer with some electronic knowledge, it almost looks like a tech has changed these 2SK76A's in a repair.
I'm going to dig out the 4 I purchased and reacquaint myself with those
 
One thing I've noticed on my studies / research of vfets and various amplifiers. There is a very big interest and following of these types of amplifiers and devices in Europe.

Particularly France and Germany. But not limited to these countries. A number of v-fet "experts" or subject matter experts seem to be in Central Europe too.

Just an observation...
 
Interesting Fez

The B2 is very prone to dust build up on the horizontal mounted Power PCB
One thing I did with my B2 was to coat this PCB with circuit lacquer, I've done this a couple of time thru the years.
It certainly helps maintaining this board in a pristine looking condition.
The B2 really looks a treat when its all polished up inside.
 
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B2 with what looks like serial number 05***
This unit has the higher domed 2SK76
(Seller has whitened out last 3 digits)
So far we are heading down to serial 5000 numbers
 
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After a look at my examples of the 2SK76A (I should have looked at my versions first)
they indeed have the domed case which is 3mm higher than the original 2SK76

The case change occurred with the introduction of the 2SK76A

If I continued going down in the serial numbers I would have ended when
Yamaha introduced the later “A” version to the B2.(which incidentally isn’t better VFet )
Higher height of the “A” version is not fully evident in this photo
 
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Pic of the VFETs in my early B-2 (serial number in the 2200's)



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The Fez said:
One thing I've noticed on my studies / research of vfets and various amplifiers. There is a very big interest and following of these types of amplifiers and devices in Europe.

Particularly France and Germany. But not limited to these countries. A number of v-fet "experts" or subject matter experts seem to be in Central Europe too.

Just an observation...
Click to expand...

I bought mine years ago on the recommendation of banned AK member 'Yamaha B-2'.
 
Thats a very clean early B2 Mark, great looking Amp !

I very biased with B2, for an amp to run 35 years to what is minimal service is incredible, yes, the input selector switch gets a bit noisy, and the relays played up.
The mains switch arc out and a couple of lamps failed.
That’s not a bad testimony to Yamaha’s B2 build quality
 
From the owners hand book,

"no mica is used in the FEt's which are directly attached by a special process to the heat sinks giving a thermal resistance less than half that of conventional mica construction, and ensuring effective heat dissipation"

A later service sheet said to conform to International Standards this process was being discontinued
Later models had mica only
 
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