Yamaha A-1000 Repair and Info Thread

As long as there equal ie. 33vdc or 45vdc the amplifier will work. The key is equal +/- voltages.
 
33.5 is kinda low voltage for that circuit. With the main caps at 33,000µf/50 vdc I'm thinking 45vdc isn't out of line.
 
I went ahead and checked for AC on all the output collectors. Here is the results:

LP+ 73.8
LP- 0
RP+ 107.9 <------The 49.2 Vdc one
RP- 0
Oooh .. That don't look very good..
Can you post a photo of the main caps. Thats alot of AC. Electrolytic capacitors don't like AC very much.
 
Bridged rectifier D168 is the common component for both LP + and RP +. The rectifiers are suppose to change AC voltage to DC voltage. And I suspect its also leaking AC ie. a shunted diode in the bridge.
 
Here is a pic of the big caps, but not very good, my phone is old and sucks at taking pics..

IMG_20170907_215403105.jpg

Diodes underneath:

IMG_20170907_220017876.jpg
 

Attachments

  • IMG_20170907_220220187.jpg
    IMG_20170907_220220187.jpg
    59 KB · Views: 54
@zaibatsu , have you ever pulled the power board on one of these A-1000's? I am haveing trouble figuring out how to get it out without taking a blowtorch to it..
 
@tmsears
Yeah I did, as I wanted to resolder that whole board and remove the caps to test, it was time consuming.

You can get to everything without physically pulling the board out from memory, but you do have to remove the caps because you can't access the joints of the PCB otherwise. I removed the vertical (long) screws from the cap clamps, then desoldered and lifted out the caps, still clamped in their pairs. I used the solder sucker to remove only what was around the capacitor leads first, there's solder all the way along those copper rails - but you don't need to remove it all. You may not need to remove both pairs of caps to access what you need, just check.
 
I'd check it first. Looks to be a little easier than those 4 diodes.:rolleyes: May not have to remove those to check them with your multimeters diode tester. But you will need to remove D168 to test it.
 
Yeah I'd definitely diode test everything in-circuit first (both directions) to see if you spot anything fishy or inconsistent.

I think you can get to everything (even the 4 diodes), use some scrap wire if you need to. It's a pain to pull the caps if you don't have to.
 
No..D168 the bridged rectifier.

Response #1 Oh...doh!

Response #2 Education time: why would it not be one of the 4 gigantic diodes? I am sure there is a simple reason, but after double checking he schematic, but at the risk of sounding foolish, I am still vague on what their purpose is, if the big rectifier does it for them anyway?...
 
Yeah I'd definitely diode test everything in-circuit first (both directions) to see if you spot anything fishy or inconsistent.

I think you can get to everything (even the 4 diodes), use some scrap wire if you need to. It's a pain to pull the caps if you don't have to.

I did on the D164, but I already have it pulled "halfway out, so I have to get to the green side of the power board to put it back..any tips?
 
Back
Top Bottom