That is really good news.
Question: Does SK180 have the same quescent point (~80mV) as the SK77?
You should verrify that.
Yamaha B-1 Quickie
- Thread starter rottalpha
- Start date
That is really good news.
Question: Does SK180 have the same quescent point (~80mV) as the SK77?
You should verrify that.
vintagejapan
AK Member
That is a good point, but since I don’t have a curve tracer hard to tell with this batch.
I managed to sort out the UC-1 last night. Replaced all the C458 with C1815 and A763 with A1015
For the C1345 I used new C1345F. Meters working well, and was able to calibrate them properly. While I was there pimped it up with some blue LED’s.
At the moment don’t have a distortion meter but was able to do all the calibrations as per manual.
It is middle of summer here and the B-1 gets really hot. Was able to run it for an hour or so and really happy with the results. I will put the SK77 back to do a compare but doing all the work on the drive boards really paid off. The amp sounds sublime
Want to thank you for your help getting the right parts, I decided to get a board for the NF-4 relay. Also changed the ceramic caps on theVfet sinks Panasonic film caps. Here is a pic of the naked beast.
Attachments
Congrats, job well done
The blue lights look a bit alien to me, but that is prolly because my eyes are so used with the B-1, B-2 amber lights.
Nice decor too. Is that 10K a 100v version?
I was gonna say, one of my meters was out by 2dBs.
I did not have time to rebuild the UC-1...I will do it next time. I did noticed a bunch of old style 458's in there, so I will definetly bo back in there. I wil not change the pots...the original ones adjusted with no issue.
vintagejapan
AK Member
Thank you!Congrats, job well done
The blue lights look a bit alien to me, but that is prolly because my eyes are so used with the B-1, B-2 amber lights.
Nice decor too. Is that 10K a 100v version?
Yes, the 10K is Japanese 100 volt version.
vintagejapan
AK Member
I didn’t change the pots also, but the right meter was not working. Changing the transistors 2 tantalum and all the electrolytic fixed the problem. I cleaned the power switch and is working normally now.
The blue LED will look more subdued once the faceplate goes in.
I saw somewhere that is possible to built a curve tracer! The guy called it “frankentracer” or something like that.
I too have a unit with green boards. I found that some of the FETs on the green boards might have been replaced on my unit
Could you please look or send a closup photo of the two round metal can FETs with the black heatsinks on the green driver boards... I do not have a schematic handy and don't recall the component ID
Those two. They are not what the schematic calls for or what my other units have....only noticed them on the green boards. I actually cannot find any information on them.
TJ08, is what they are marked with.
Green boards...hmmm,
So the ones in this unit not officially replacements...Then what are they.
Does anybody know what TJ08 is...I guess I could answer my own question if I pull one and test it. My guess would be that it is a same channel FET, but is it a close match for the sj24?
I guess I will find out at some point. BTW, both boards have same replacement and both boards come from a unit with a failed SK-180 replacement attempt
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One additional observation:
The lk15 next to it..It is color coded for rank. The same trannies in this unit and in Vintage Japan boards have letters for the rank, not color...
My guess is that the TJ08 was early production version of the 2SJ14. I don't think the failed K180 replacement attempt is related.
My guess on the failed K180 attempt is that someone didn't fully understand how to set up for the K180's properly and they failed as a consequence ... but that's just a guess on my part.
clinic-audio
all on YAMAHA untill 1990
Hello
On all the B1 I have refixed , I never seen V FET marked TJ08
Here is what every driver boards look like :
On all the B1 I have refixed , I never seen V FET marked TJ08
Here is what every driver boards look like :
vintagejapan
AK Member
This is strange, on one of my boards those transistors were replaced with MPSU60 motorola.
Are you sure? Look at it again since that wouldn't work.
vintagejapan
AK Member
Yes, 100% I have since pulled them out but am certain about this.
clinic-audio
all on YAMAHA untill 1990
YES this is a part of many mysteries in parts list of service manual
a MPSU60 can't replace a FET or VFET
A FET or VFET can't be replaced by a bipolar transistor
a MPSU60 can't replace a FET or VFET
A FET or VFET can't be replaced by a bipolar transistor
oh, I know that is not why the SK-180s failed. They failed due to operator error 100%. I have one dead on each channel. .The remaining most likely not a pair.My guess is that the TJ08 was early production version of the 2SJ14. I don't think the failed K180 replacement attempt is related.
My guess on the failed K180 attempt is that someone didn't fully understand how to set up for the K180's properly and they failed as a consequence ... but that's just a guess on my part.
The TJ08s are probably NOT original Yamaha replacements. The reason the original J24s were replaced is probably opertor error as well.
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Thank you Patrice,
that is why I am checking in with you guys. I have six B-1s with only one has the green boards and the TJ8s...but you all helped me confirm my hypothesis about the TJ8s.
I would like to point out is that not all boards look like the one you are showing. As Alex and Nick pointed out, and as I was able to observe on one of my units, some of the boards can be green.
View attachment 1096637
one more observation Patrice:
in these green boards, the LK15 and the LJ13 have rank letters, where on all other units I see color markings for rank.
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clinic-audio
all on YAMAHA untill 1990
OK
What kind of 2SK75 do you have on all your driving boards (green PCB and others) ?
LK15A IDSS 8,00 to 9,00 mA color code RED
LK15B IDSS 9,00 to 10,00 mA color code BLUE
LK15C IDSS 10,00 to 11,00 mA color code ? Did not made any measurements yet
As you can see 1mA difference , very very tight
LJ13A IDSS 2,5 mA to 3,5 mA color code RED
LJ13B IDSS 3,5 mA to 4,5 mA color code YELLOW
LJ13C IDSS 4,5 mA to 5,5 mA color code BLUE
What kind of 2SK75 do you have on all your driving boards (green PCB and others) ?
LK15A IDSS 8,00 to 9,00 mA color code RED
LK15B IDSS 9,00 to 10,00 mA color code BLUE
LK15C IDSS 10,00 to 11,00 mA color code ? Did not made any measurements yet
As you can see 1mA difference , very very tight
LJ13A IDSS 2,5 mA to 3,5 mA color code RED
LJ13B IDSS 3,5 mA to 4,5 mA color code YELLOW
LJ13C IDSS 4,5 mA to 5,5 mA color code BLUE