the SK75s are all the same...
A-rank for the ones on the center
B-rank for the ones on the heatsink
thank for providing the ranks for the smaller fets. I did not make any measurements yet...still in the discovery mode
Yamaha B-1 Quickie
- Thread starter rottalpha
- Start date
the SK75s are all the same...
A-rank for the ones on the center
B-rank for the ones on the heatsink
thank for providing the ranks for the smaller fets. I did not make any measurements yet...still in the discovery mode
what is the IDSS / color rank for the J24?
vintagejapan
AK Member
I was surprised myself when I saw it. The board was a early revision also.
vintagejapan
AK Member
I installed the SK77 yesterday and after adjustments had a good listening. I am using a tube pre and the direct in inputs. To my ears the K180 has a smidgen more extension on the high. All the rest is identical.
The only issue I have is that this B-1 does get very hot. The fact that there is around 30 degrees celsius everyday surely does not help. So after running it for a couple of hours the amp need to cool off before can be turned back on. Is this normal?
Here is a close up of the drive boards.
The only issue I have is that this B-1 does get very hot. The fact that there is around 30 degrees celsius everyday surely does not help. So after running it for a couple of hours the amp need to cool off before can be turned back on. Is this normal?
Here is a close up of the drive boards.
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vintagejapan
AK Member
Thanks for the comparison!
Yes the B-1 runs quite hot. So much so that in my case I rotate in my B-2 in the late spring here because of how much heat the B-1 contributes to our already very hot home during the summer; that and I also love the sonics of the B-2 and this way I get to enjoy both. Albeit moving a B-1 around is a real pain in the back ... and a few other places!
Very nice indeed!
vintagejapan
AK Member
My pleasure Nick,
At list now I can keep this one going. To my ears, B-3 run as 2 mono blocks would be next in line after the B-1. And they do run quiet cool.
At list now I can keep this one going. To my ears, B-3 run as 2 mono blocks would be next in line after the B-1. And they do run quiet cool.
vintagejapan
AK Member
what is very hot? if the thermo switches are puting the amp in thermal protection, that is not normal
the unit I worked on for this thread was getting extremely hot, but not turning off. It was obviously on its last legs and most likely out of adjustment.
My understanding it that the bias balance pot will help balance out minor differences within a output v-fet pair. That will ensure that one of the devices does not work more than the other and overheat. It will also bring down THD.
edit: while testing the unit I did let it on hooked to the generator for a long period of time at 75w otput. The heatsinks weare at a toasty 160deg F, but everything seemed normal. But again, if you do not need a room heater when you have 30deg C outside, do not play your B-1
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I meant to say, Thank you for the close-ups. I see the fets rank marked with letter.
nice job bringing that bad boy to prime again
Where did you come up with all this stuff?so bunch of "strange" fets and v-fets in there ...and the TJ08 mistery solved. Tried to find informaion on it and I found nothing.
so interesting. I am willing to bet that the Y304/405 devices were from your green boards? correct?
if my assumption is correct, the Y304/405, the TJ08 and the letter ranked J13/K15 devices were used in the earler B-1 units.
Beau Geste
Italia
I see an IEC320 socket on the back of the Power Amp. Is there a special tool to cut it out of the sheet?Thanks.
vintagejapan
AK Member
“Cannot held hand on top of the heat sink” hot.
The unit does not turn off, but if I turn off will not turn back on until cooled a little.
I will check the p-p balance settings again.
The unit does not turn off, but if I turn off will not turn back on until cooled a little.
I will check the p-p balance settings again.
vintagejapan
AK Member
Not as detailed as your restoration work but will do for now
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vintagejapan
AK Member
I used the hole for the connector to power up a suitable preamp (C-1) and just filed it to make it a little wider.
I am wondering if the YT304 were other v-fets later replaced by the toshibas.
Maybe @ilimzn would know
That's definitely not good! During the summer my B-1 gets too hot to keep my hand on the top cover but it never shuts down and will play beautifully for days that way and stay rock solid as far as bias and offset go. I'm thinking the bias still isn't set properly ...