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Post by mastertech on Mar 13, 2016 18:45:06 GMT -5
Lets recap so we are on the same page. Volume at minimum.
On the drive board:
TP1 and TP3 =
TP2 and TP3 =
On the electrolytic capacitor board:
TP1 and TP3 =
TP2 and TP4 =
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nashou
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Tech in Training.....
Posts: 1,239 
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Post by nashou on Mar 13, 2016 19:04:11 GMT -5
Think I figured out why no voltage on the left channel idle current. R113 is open . In circuit it measured 2.3 k ohms. removed it and it was OL and no continuity, just to be sure. I am going to replace all the .47 ohm'ers 5 W with new ones. I went through and re did all the adjustments to speck. , And during all this i noticed that the left was fluctuating way more than the others. So when I realized that there was no voltage for the left channel idle current I knew something was wrong there. The two test points read current between LO and CE from looking at the PCB board drawings and physically looking at the actual board. Looking at the schematics I see that R113 and R114 connect to LO signal. But only R113 is between the two signals. Sure enough that resistor is dead. How was that Mac?  Hopefully there will be no more surprises. I do have a 1 ohm 5 watt resistor I took out of a speaker cross over I re worked. can I use that for testing purposes? EDIT: I'll add this here On the drive board: TP1 and TP3 = .1 mv TP2 and TP3 =2.3 mv On the electrolytic capacitor board: TP1 and TP3 = 0.0 mv ( no reading on left channel) TP2 and TP4 = 7.6 mv after adjustment Nashou |
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Post by mastertech on Mar 13, 2016 20:05:20 GMT -5
Good job!  You should be able to test with that 1 ohm resistor. |
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nashou
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Tech in Training.....
Posts: 1,239
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Post by nashou on Mar 13, 2016 20:17:44 GMT -5
Good job! You should be able to test with that 1 ohm resistor.Sweet. I'll install it and see if I can adjust the Idle Current. Oh And thanks Mac.  Nashou |
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nashou
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Tech in Training.....
Posts: 1,239
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Post by nashou on Mar 13, 2016 20:51:29 GMT -5
Woo Hoo!!! Works, only thing now is the right side Idle current is higher by about 3-5 millivolts. I think its because of the 1 ohm resistor on the other side. I can't adjust it down it reached the end of the adjustment. I think once I get the new Ohmite Audio Gold Resistors it will adjust fine. www.partsconnexion.com/prod_pdf/ohmite.pdfNow on to the Yamaha A-3 after this is put back together. Athanasios |
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Post by mastertech on Mar 13, 2016 21:01:16 GMT -5
Oh And thanks Mac. Nashou welcome. |
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nashou
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Tech in Training.....
Posts: 1,239
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Post by nashou on Mar 22, 2016 21:23:17 GMT -5
Ok Another issue, but I think I know what it might be. Even with no source connected the right speaker will begin to pop,snap and crackle. I think it might be the relay. On Audio karma another Yamaha tech mentioned it might be the voltage as well going to the relay, And I did notice the two regulators on the power board are loose in there heat sink housings. Maybe they are over heating or the caps to them are going bad. I had already planned on recapping that board and have them in stock. So I'll do that board , but first I'll tighten the regulators down and test a bit. I forgot the amp on all night the other day and heard the noises coming from the basement, I thought some one was braking in to sliding doors. It was the amp, and it blew another of the power resistors(.47 ohm ones) on the right channel this time and it created the same issue, static all the time. I replaced them and all is well except for that intermiten crackling. Here are the new Audio Gold resistors. .47 ohm 5 watters .  I also ordered all new bourns trim pots for setting all the voltages and offsets. And new relays, enough for both my A-1's Once this unit is humming along i'll do the same to my original one with the phono issues. I did not clean the switches as well on that on as I did with this unit. |
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