Discussion in 'Yamaha' started by tmsears, Apr 13, 2017.
Yeah, a little on the pricey side, but not terribly so. Good find!
I went ahead and ordered a pack of the above-mentioned resistors, as it seems to be nearly impossible to find them in that value and form factor anymore. At least this way I won't have to worry about folding the resistors over accidentally when I work on our near the phono/eq board, as they do stand off a good ways above the board. I still don't know what I am going to do about the bridge rectifiers though. Maybe I could buy four diodes and whittle my own?
Well, for bridge rectifiers, the only one I saw on mouser that fit the bill was the 905-BR62
I think it should work as a replacement for both bridge rectifiers.
Since I will have to go back into the power supply board, I thought about replacing the 4 rectifier diodes as well. I am stuck between these two:
The only issue is the first one is 1.3 max forward voltage instead of 1.0 With the second one I get to the original forward voltage, but it would drop my surge current from 200 to 150 A.
I don't know which value is more important...
If there is anyway if cleaning it up to make it less "family circus" I would be happy to hear them for sure.
Well, the new power resistors for the eq board arrived yesterday. A slight modification was required:
In addition to the leads being double pronged instead of single, the legs are a lot longer than the originals. They still clear alright, and hopefully the added length will help dissipate heat more efficiently in that area:
When the new rectifiers come in I will re-post the voltages and maybe I can get some help with further troubleshooting at that time.
Kudos go out to @zaibatsu , @avionic , and @Hamish119 for there expertise and guidance. I would not have gotten this far without their help.
Well, the rectifiers arrived yesterday. I must live close to the warehouse; it's like Wiley Coyote and the Acme Co. On ship times here, on ground UPS.
Anyway, got those installed and the caps resoldered on.
No pic but I had to trim the ground leads as most of the ends had corroded, some more than others. I have no idea how they could corrode underneath solder but they did.
It was late when I finished so I will look over my work and take some voltage readings later tonight and provide an update.
Well, somehow the AC coming out of the DC outputs of the (new) rectifiers is now DOUBLE what it was before I replaced them. This doesn't make any sense...
That's strange, they look like they're in the right way.
I wonder if any of C179, C180, C181 metallized mylar caps might be shorted.
Can you remove and check those on your component tester?
D167 1SS82 -> BAV21 by the way. If there's any suspicion of that.
I'm thinking your AC issue is a wild goose chase..
Maybe a recap of where you are now and what symptoms you're going after would help everyone catch up. Since this is a general thread there have been a bunch of posts in between so it's a bit hard to follow.
I'm working on an A-700 right now that had all sorts of weird problems that turned out to be dry solder joints pretty much all over the place. It would randomly go into and out of protection with differing amounts of DC on the relay terminals, sometimes the dim bulb would be dim, other times it would pulse, sometimes it would just be bright.
Not sure if you've gone over the boards but this particular amp was the most solder cracked piece I've ever worked on. If yours is anything like this it could very well be some of your problems.
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