Yamaha A-1000 Repair and Info Thread

You've got two rectifiers:
Large one should be D5FB20
Small one should be 4D4B41, but double-check, may be something else

I attached the data I could find for both.
You can at least get a feel for the numbers and find some possible candidates while you wait for confirmation.

From my understanding, Vrm (rep. peak reverse voltage max), Ifsm (forward current max), and output current should both be equal or better on the replacement part, and Vf (forward voltage) should be close to the same.
 

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  • 4D4B41.png
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Hardly.. I have a C-2a,C-4 and a M-2 that have priority over your 1000.
I figured you were busy, so I decided to crack wise.:rolleyes: But then again I wouldn't blame you for running away either! At least we all now know that I can blow stuff up properly. :biggrin:
 
This thread has gotten so confusing.

Sorry about that. I was trying to fix the issue of 128 volts of AC being dumped out of the positive DC side of a rectifier and into the connecting main filter cap. Hamish helped be troubleshoot the voltages and they are not right in several ways, AC being where (I think?) it shouldn't be. Hoping to get it out of protect mode by replacing a resistor to fix the -22 and the rectifiers to stop the AC going everywhere, but the rectifiers are difficult for me to substitute since I don't know what to look for in the way of values.
 
You've got two rectifiers:
Large one should be D5FB20
Small one should be 4D4B41, but double-check, may be something else

I attached the data I could find for both.
You can at least get a feel for the numbers and find some possible candidates while you wait for confirmation.

From my understanding, Vrm (rep. peak reverse voltage max), Ifsm (forward current max), and output current should both be equal or better on the replacement part, and Vf (forward voltage) should be close to the same.

Thanks much. I found the same said specs online, but the "what to look for" part has me stumped, but maybe this will help. Can you go higher in output current? I plug in the style and the output current and it narrows the results to 0 in mouser.
 
I'm watching with interest what you find out. Sounds like you might be fighting with two issues between the hum and then the bias transistor shorting.
The one I picked up was Chernobyl'd in the normal way thankfully so no huge troubleshooting was needed on my part.
Yeah, I can't say for sure but it seems to me that the hum and the rectifier trouble was probably a "creeping" issue that probably came up fairly recently, but, that is just a guess. In my career with computers it was not uncommon to fix one hardware problem only to have a simultaneous yet completely different problem pop up at the same time or shortly thereafter - and sometimes, the problem was there all along, manifested during troubleshooting something else. I would think that would also be possible in audio repair, albeit on a different level. I'm glad yours had a more straightforward issue.
 
I haven't really added much to the A-1000 thread so I'll add how I handled my BBQ board. It seems like my amp hadn't been run much at all prior to having one channel short but I wanted to head off the board discoloration before it could take hold.
I bought a set of lead bending pliers and used the 1 watt resistors mentioned by Zaibatsu above. The results turned out pretty nice IMO.

image3 - Copy (4).JPG
A-1000 BBQ Board.JPG
A-1000 resistor.JPG
A-1000 BBQ Board done.JPG
 
I haven't really added much to the A-1000 thread so I'll add how I handled my BBQ board. It seems like my amp hadn't been run much at all prior to having one channel short but I wanted to head off the board discoloration before it could take hold.
I bought a set of lead bending pliers and used the 1 watt resistors mentioned by Zaibatsu above. The results turned out pretty nice IMO.

View attachment 1039525
View attachment 1039519
View attachment 1039521
View attachment 1039522

Very nice job on bending the resistors, a lot better than I did mine. Did you bend them that way to make sure they were all at the same height?
 
I was originally going to stick something under them to make sure they were the same height until I found those lead bending pliers. I also like the way they look with the little half bend and figure the pliers can be useful for other things as they pop up.
 
I was originally going to stick something under them to make sure they were the same height until I found those lead bending pliers. I also like the way they look with the little half bend and figure the pliers can be useful for other things as they pop up.
That's a pretty cool find!
 
Does anyone have any recommendations for replacement for 1.8k, 5 watt Ohm wirewound resistors? The only one I pull up are the newer epoxy dipped kind, the ones in the unit now have wide, formed legs for riased height and are of the "sandbar" variety, which I can't seem to find in either mouser or digikey.
 
https://mouser.com/ProductDetail/Yageo/SQP500JB-1K8

This is the closest I could find in factory cement moulded wirewound type.
I can't find the radial leg type (on mouser) in 1.8K.

You'd have to fold legs so they come out slightly below the resistor (to match the PCB spacing).

You could also fold the surplus leg up against itself neatly to double its width (instead of cutting) and lightly solder to provide a bit more support. With some time it could be done neatly. Don't think it really matters though, as long as you mount them up off the board the same height as the stock ones.

Unfortunately not in stock until Dec 7th, maybe you could look elsewhere if needed sooner. Using the keyword "cement" helps.
 
https://mouser.com/ProductDetail/Yageo/SQP500JB-1K8

This is the closest I could find in factory cement moulded wirewound type.
I can't find the radial leg type (on mouser) in 1.8K.

You'd have to fold legs so they come out slightly below the resistor (to match the PCB spacing).

You could also fold the surplus leg up against itself neatly to double its width (instead of cutting) and lightly solder to provide a bit more support. With some time it could be done neatly. Don't think it really matters though, as long as you mount them up off the board the same height as the stock ones.

Unfortunately not in stock until Dec 7th, maybe you could look elsewhere if needed sooner. Using the keyword "cement" helps.
Yeah, I usually filter my search results to only show parts in stock, so that would explain why I couldn't find any. Neat idea about the leg folding though.
Would the epoxy dipped type work if I increase the wattage to, say, 10 watts?
 
I'd go with that ^^
Otherwise yeah, just run the highest wattage epoxied wirewound that'll fit, 10W is fine.
 
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:

583-FR302-T

625-UF5401-E3

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...:confused:
 
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