Discussion in 'Yamaha' started by tmsears, Apr 13, 2017.
Did you replace the 4 large caps ?
See if there is any AC voltage there.
Well, I'm not a pro but I will bet it is a error in the schematic, if only for no other reason than it not making sense to have one voltage higher in one channel as opposed to the other...but then again, what the heck do I know? maybe their is some crazy electro-reason? Maybe, but something tells me it is a coincidink.
Yes, I have in on a dimbulb, 100watt. I figured that would be safest, but I can always try it without if that would help.
I will check on it next.
No sir, I did not.
As long as there equal ie. 33vdc or 45vdc the amplifier will work. The key is equal +/- voltages.
I went ahead and checked for AC on all the output collectors. Here is the results:
RP+ 107.9 <------The 49.2 Vdc one
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.
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.
Gonna have to pull that one to check it, aren't I..
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.
Might as well check D163 as well.But I'm leaning toward D168.
Here is a pic of the big caps, but not very good, my phone is old and sucks at taking pics..
You mean 164?
I am going to have to pull the whole power board to get to this, aren't I?....
@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..
No..D168 the bridged rectifier.
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. May not have to remove those to check them with your multimeters diode tester. But you will need to remove D168 to test it.
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