Yamaha B-1/UC-1 & C1 Recap

Bungles

Member
It's finally time to refurb my beloved B-1 amp and C-1 pre-amp. I am looking for some detailed information on what the best things are to replace & check. I remember seeing some great threads a few years back on the subject but now I am unable to find them so I'm reaching out to my fellow AKers.

I'm having all the relays replaced for sure but I need to know what else needs to be done.
 
It's finally time to refurb my beloved B-1 amp and C-1 pre-amp. I am looking for some detailed information on what the best things are to replace & check. I remember seeing some great threads a few years back on the subject but now I am unable to find them so I'm reaching out to my fellow AKers.

I'm having all the relays replaced for sure but I need to know what else needs to be done.

First. Get the service manuals. Heed all the cautions and warnings pertaining to discharging capacitors before unplugged and reinserting CCA's and assemblies with the B-1.
 
Hello bungles

as Avionic says, get service manual (original if you can because high quality of schematic and text in many pages is important )

About B1

2) recaping is a good idea if it is done the way it should be . The main problem with B1 is the double electrolytic type (15000MF/15000MF/100V) . Many get shorted ( or bad ) without advice you before and then damage one of the 2SK77 FET.
3) give us (in private message if you prefer) all the PCB numbers because different models does exist and I don't want to say something wrong to you .
4) do it step by step board by board (take you time ) and do not switch on before to have replaced these both capacitors (15000MF)
About C1
This is a serious job to do and I will strongly recommend you to do it like in B1 (board by board , taking your time )
Last time I did it, I spend more than a complete day to do a C1 !
Be carefull because there is many BP ( non polarized cap ) in C1 and don't make any mix .
You will find a lot of bad soldering on the bottom of the power supply board again do it slowly .

I have 2 B1 for repair here , ready to be use , already recaped , just waiting for new type of 15000MF/15000MF/100V !

UC1 is not complicate .

do not hesitate to come back to us if you need anything , Avionic , vint age and I are reading your message with a big interest !
 
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It's finally time to refurb my beloved B-1

I don't have a C-1 so I can't comment on it but last fall I found this beat up B-1 that spent its life as a bar/club amp and was on its way to becoming a boat anchor. After a good recap including the dual 15,000uF main power supply caps which I discovered were about to fail, a few new resistors, a new output relay, and a few other things and I got it back up to spec and sounding sweet. I posted some pictures of the process in this thread:

http://www.audiokarma.org/forums/showthread.php?t=427473
 
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Hello Bungles

Here is some picture about C1

1) Power supply PCB recaped yesterday
2) bad non polarized coming from tone control amp pcb , see what the time can do on a simple capacitor...
3) I told you to be very very carefull during recaping your unit because 2SK78 TR are really sensible and legs can be easely broken , see my pictures 3 and 4
...:thumbsdn:
5) picture of two different PCB coming from a C1 that I am repairing . Both PCB are NA067190 but they are not really the same boards with differents components ! some are different other are missing ....Strange no ?

I have 4C1 for repair right now ...:scratch2:
 

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3) I told you to be very very carefull during recaping your unit because 2SK78 TR are really sensible and legs can be easely broken , see my pictures 3 and 4
...:thumbsdn:

:yikes:

Looks like you tried to solder the leg back on with no success. :tears:

5) picture of two different PCB coming from a C1 that I am repairing . Both PCB are NA067190 but they are not really the same boards with differents components ! some are different other are missing ....Strange no ?

Strange yes. :D

I have 4C1 for repair right now ...:scratch2:

Double :yikes:
 
YAMAHA C1 recap

hello !

Looks like you tried to solder the leg back on with no success
I know that this is not possible but I tried , yes ! I did because the 2SK78 was good :tears::tears:
So it was necessary to put a new one . No other way ! :thmbsp:
 
YAMAHA C1 recap

Hello Avionic !

Are they working ? waiting to be refixed ?
I have one pair ( again ! ) of C1 who will arrive here from Germany in some days .....:banana:
They come to be controlled and repaired :scratch2:
If I am lucky I will make a picture of 6 (!) "rare" units !:yes:
 
Ones serviceable the other one has no phono and a missing channel going through the tone control.Put it in tone by-pass I get both channels.Chasing through the schematic is a nightmare.Even with the schematic blow up to 1.0m X 1.3 m. :D
 
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