vintagejapan
AK Member
Thank you Pete,
Am waiting for some parts and should be firing up the beast soon.
I have just completed the power supply boards 1&2.
Will let you know how I go
Yamaha B-1 Quickie
- Thread starter rottalpha
- Start date
Am waiting for some parts and should be firing up the beast soon.
I have just completed the power supply boards 1&2.
Will let you know how I go
vintagejapan
AK Member
I also had a faulty MPSU60 on the power supply board 2 which I replaced this with a MPSW92.
vintagejapan
AK Member
that would work.
vintagejapan
AK Member
Well, the capacitor kit from Clinic is in. I have finished the power supply boards 1&2. A quick test and the-200 volt and +40 are showing up nice and steady on the power supply board #2. Also managed to adjust the 12v, -25 and +25 on power supply board #1. I have a weird issue though. When I turn off the power switch the amp stays on for few seconds. Then turns off. Not sure what to make of it.
I checked the switch and the connection with the UC-1 and found no issues.
I checked the switch and the connection with the UC-1 and found no issues.
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That main caps kit sure looks nice.
I think you are on the right track with troubleshooting. I would look at the switch and the protection circuit, including that solenoid.
the question I have is how were you able to adjust the voltages if the power turns off so quickly??
FYI, I powered averything up with a DBT and a variac, all the way to the driver boards.
vintagejapan
AK Member
That main caps kit sure looks nice.
I think you are on the right track with troubleshooting. I would look at the switch and the protection circuit, including that solenoid.
the question I have is how were you able to adjust the voltages if the power turns off so quickly??
FYI, I powered averything up with a DBT and a variac, all the way to the driver boards.
I think the power switch may be the culprit.
When I turn the power ON remains on, but when I turn the power OFF just lingers for a couple of seconds before the power cuts off.
The 3rd protection board is in, now the real fun begins...
vintagejapan
AK Member
Well, the protection test went well last night.What's taking so long
Now I get to ask that question
Just finished the filter board.
Used 2SC1815 and 2SA1015 to replace the C458 and A763 transistors. Still need to source the relay.
Also replaced some of the ceramic caps with silver mica.
Pondering now on the first drive board.
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man that driver board looks roasted
There are 2 types driver boards out there in B-1's, the more common light coloured ones and the rarer dark coloured ones.
Btw, there are at least 4 different B-1 iterations/updates of the rear panel variations I seen so far
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vintagejapan
AK Member
The photo was from late last night and lighting was not ideal.
VintAge is right, there are 2 type of boards and I am using a light one for the filter but dark green for the driver
Here is a better shot of the driver board.
Thank you Pete for your help with the heat sinks
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to me your driver boards looked diferent from eachother. I do not think is the lighting and I am not looking at the filter board...I am looking at two B-1 driver boards.
Just an observation...
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It took me months to come up with that unique design 
I meant to say, I see the deep green color and I was not aware of it before, so maybe that is why it looked toasted. I have a few boards here that are well toasted, that started to look like that, but not because of the factory color being differnt.
vintagejapan
AK Member
Yes, there is 2 types of driver boards in there. I have a pair that is light color and a pair that is dark green one.
Managed to finish the boards late last night and do all the adjustments. Everything looks a ok! Adjusted the bias at 80mV and the DC at 0 volt. This is with the SK180 Tokins.
There were multiple issues with this B-1. Now Have to sort the UC-1 unit. The switch issue has settled in and amp turns on and off normally now but the right meter is not moving. I will remove all the mediocre speaker connectors from the back panel and install a IEC power input. While in there will also get to the couple of the switches on that input board. The body of this B-1 is in pretty bad shape, will most likely do a coat of paint.
Also need to get a new relay for the filter board.
Pete, where did you source yours from? I also seen that a board can be made and so able to install modern replacements
I have seen them come up for sale on the fleabay US and Hong Kong. I got mine on fleabay US. They come in yellow or transparent pastic casing.
Replacing with modern components would be a good alternative, if you can get an adaptor board.