Yamaha A1 power switch , and static L Channel: FIXED

Ok, left channel is the bad one, right?
When you blew the right channel TR1 and TR2 you replaced them with new, correct?
Have you tried replacing or swapping TR1 and TR2 on the left channel?

Yes, and so does the CHMI board. It is time we get this narrowed down. If distortion still there after left TR1 and TR2 change then on the drive board i want you to swap C507 and C508 and recheck distortion. If no change post back and i will give next suggestion.

I installed new TR1 and TR2 on the left channel and it still have some distortion on the wave form for -E and +O . but not as bad.

So I decided to look at the DC on the outputs as I was still thinking about the DC offset adjustment. Well I got 1.7 volts DC on both Speaker outs!!!

SO what do I do being the adventurous person I am. I hook a speaker to see what the Eff is up.

To my surprise no distortion or scratchiness on either channel. So now I am going to use the 8 ohm 100 watt power resistor i bought attach it to a large 5x4 heat sink I bought and adjust the
DC offset to see what the Eff is up.

Any other advice? And i have to say it sounded pretty good but i didn't raise the volume to high and I only used one song from Corrine Bailey Ray, I wanted more of a vocal and clean
recording , or other words no hard metal rock .

Any advice on what to do next if I can not get the DC down on the speaker outs?

Nashou

What do you mean?

False alarm any how, After I set the DC offset's the volume board was way off and so was the drive board. those are set now.

I tried to set the idle current but not sure I am doing it right. I can only see two test pins. 

Oh God, I just realized I am not sure if I swapped the load over to do the other channel. I think I did the right and not the left.

Ugh!!!

I'm an idiot. 

I'll go back down and re check them. I think that is why it sounded good before and then I THOUGHT I was setting the DC offset right. But I forgot to swap the load over.

I hope that was It. 

In the mean time maybe you can help me figure out the Idle current test procedure. I used the Chassis as GND, and Test point one and two.

It says 7.4 +/- 2mv  IS that 7.4 Volts DC?

Nashou

I would think that idle current should be mv but test and see what you have.

no just 1.2 and 3 . I think 3 is GND. its what I used.

On the Idle current I got .003 vdc and .345 vdc. Something is not right some where and on the one that was .345 it went all over the place from 12 vdc then to OL then to 7 then stabilized at .345.

I'm tired and have to get up early. I will read up on some stuff so if you have any ideas now I guess post them and we can try tomorrow after I get done with work.

I must be doing the Idle current test wrong or soemthing.


Nashou

Ok I was able to adjust the idle current for the right side ( Board drawings have it back wards) TP-2 and TP-4(RO)

however no change for the left Channel . I wonder if this is the issue? not being able to adjust the idle current may be overloading the Drive board?

Stepping out for a bit be back in an hour.


Nashou