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Yamaha B-6 Repair attempt and then we'll see...

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It also showed up with the original triac replaced. Thankfully they included it in a bag. The repair attempt wasn't as aweful as some others I have seen, but I was suspicious. I tested the triac with a multimeter and it seems fine. I don't know if there is a suitable replacement for the original triac, so I reinstalled it. Fixed some cracked solder joints on the the bigger rectifier and some other things. Decided to start at the power supply, because if the triac is shot then we have to solve that first.
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Thankfully, it appears that the original triac is ok. The power supply seems to work. The voltages are a bit off, but I think that is likely because the load and rest of the circuit is not connected.
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I'm happy to work with you on this if you need some assistance / compare notes and voltages :)

Few things to note I found is that you can run the power supply separately from the mainboard and keep it isolated until the voltages are stable... Some of the supply capacitors are probably leaking / shot. If it refuses to start and stays locked around 50W draw, I found D503 bridge rectifier likes to fail (I've been through a few in my unit from turning it on and off many times). Not sure you could find a replacement for the triac with the same dimensions and the blue potted Yamaha IC is unobtanium so hopefully it's fine.

Can find videos of my work so far here:

IMG_4798.jpg


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Yamaha B-6 Amplifier - Restoration

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WCGW said:
I'm happy to work with you on this if you need some assistance / compare notes and voltages :)

Few things to note I found is that you can run the power supply separately from the mainboard and keep it isolated until the voltages are stable... Some of the supply capacitors are probably leaking / shot. If it refuses to start and stays locked around 50W draw, I found D503 bridge rectifier likes to fail (I've been through a few in my unit from turning it on and off many times). Not sure you could find a replacement for the triac with the same dimensions and the blue potted Yamaha IC is unobtanium so hopefully it's fine.

Can find videos of my work so far here:

View attachment 3399977


youtube.com

Yamaha B-6 Amplifier - Restoration

Share your videos with friends, family, and the world
youtube.com youtube.com
Click to expand...
Awesome, thanks for replying and making those awesome videos! I have really enjoyed watching them, and just like all great series I can't wait for the next episode to be released!

FYI, the pre drive boards in this amp look much better than the main board does, just like in yours. Maybe the pre drive boards were made by another company or at a different facility.
 
Nashou66 said:
Check the solder joints on the PS especially the Bridge rectifier.

Look for my thread on my Basket case B-6 I repaired , twice ;)

Athanasios
Click to expand...
Aren’t they all basket cases hahaha. I dunno the more I dig into mine though, in some ways it’s easier to work on once its stripped down and all the thermal paste is gone.

I finally found the photocoupler adjustment measuring points no thanks to that stupid service manaual
 
wow thats a great one! These things love to break solder joints and glad I reflowed everything… Forgot to mention also don’t do an xraytony and replace the filter caps without insulators under them…I almost made that mistake lol :)
 
On the Filter cap board are a bunch of R's that get hot and scorched the board, some of mine were way off value .
Replace with metal film and raise them off the board like this.


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I like the idea of replacing the output transistors with resistors to test the repairs of the amplifier. @Nashou66 used 2 watt 470 ohm resistors in his B-6 to do this.

Is this a good idea? How is the right resistance for this determined?
 
Never considered doing that, one thing to keep in mind is at some arbitrary point, the output transistor collectors are going to switch to the high voltage rails and that seems to be when the party happens from what ive seen as my HV switching transistors have been replaced on both sides on mine… I haven’t got there with mine yet but I was hoping to run it with no load and hopefully they switch over still?

Other than different rail switching transistors, I also found these 2 resistors had been changed from 150ohm to 1.15k ohm. Haven’t worked out “why” yet…

I changed those resistors also and raised them :)

resistorchange.jpeg
 
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