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Post by mastertech on Dec 4, 2016 21:17:29 GMT -5
It should be zero volts.
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nashou
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Post by nashou on Dec 4, 2016 22:34:16 GMT -5
On both sides of the resistor ? |
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Post by mastertech on Dec 4, 2016 22:50:56 GMT -5
yes.
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nashou
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Post by nashou on Dec 5, 2016 10:24:03 GMT -5
Now that is with the resistor in right? What is it with the resistor out?
Nashou
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Post by mastertech on Dec 5, 2016 11:40:59 GMT -5
Same. That is your audio out line and should have 0 volts. When there is this much - or + voltage on that line, that is why it is blowing the FET.
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nashou
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Post by nashou on Dec 5, 2016 12:09:02 GMT -5
Same. That is your audio out line and should have 0 volts. When there is this much - or + voltage on that line, that is why it is blowing the FET. Ok Thanks that helps me understand more and what to look for while going over the schematics. I was thinking or removing the switch but I can't see how it alter the voltages there. It almost looks like I might have to change every part there. Is it possible for a capacitor to measure fine in my parts tester but fail while under load? And can some caps be taken out and the circuit work fine for testing volatages? Liek the non polar caps that is? Nashou |
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nashou
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Post by nashou on Dec 5, 2016 20:02:18 GMT -5
Ok Trying to figure out the area of TR 109,111,113,117,115, and added TR101 to the mix.
I wanted to isolate TR113 and TR117 some what from each other so I removed R149 and R151 and left R 139 in place.
R 137 and 138 are still out. Im just looking at the left channel here.
I'll start in numeric order of TR's
TR 101
B= 24.66 C= 25.15 E= 25.28
TR 109
B= 24.93 C= 11.94 E= 25.21
TR 111
B= 23.01 C=-25.06 E= 11.59
TR113
B= -25.26 C= 25.33 E= -1748
TR115
B=-24.75 C=-25.42 E=25.42
TR117
B= -25.34 C=-25.35 E= -25.07
Not sure if this helps, should I remove R139 and re test some of the TR's?
EDIT: Ok after the amp was off and I was studying the schematics. I retested TR109 and 111 to see why have the 11 volts there
when it should be higher. So Right on turn on I have my probe ready on TR 109 collector. it read 23.8 and stayed there for a few minuts then collapsed to the 11.89. WTF??!!!??
Nashou
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Post by mastertech on Dec 5, 2016 20:39:20 GMT -5
Think of this as a battle, a battle between positive and negative voltage. Both voltages are marching towards each other until they meet. And for now they meet at R139. Once they meet they stop moving. So when they are moving they are for this instance + and - 25 vdc. When they meet and stop it becomes zero volts, or in this case + and - 1.1vdc as shown in the schematic. R139 is a buffer to ram into.
What you have is the - voltage is overpowering the + voltage and pushing it back as far as between TR109 and TR111 as indicated by the 11v instead of 23.3v. So we are trying to figure out why the + voltage is loosing strength.
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Post by mastertech on Dec 5, 2016 20:43:07 GMT -5
I'm wondering if we should try disconnecting that servo section and see if it make a difference.
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nashou
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Post by nashou on Dec 5, 2016 20:51:42 GMT -5
I'm wondering if we should try disconnecting that servo section and see if it make a difference. How does a servo amplifier work and why is it used? And what would disconnecting it Isolate. I thought the voltage shift might be caused by those super hot transistors , but looked at the voltages there and everything checked out fine there. Could one of the caps be the reason? I noticed C113 has a loose leg but when I took it out it meausred fine even when wiggling it, and its not in that part of the amp I was looking at. |
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Post by mastertech on Dec 5, 2016 21:03:20 GMT -5
Well it is my understanding that the servo circuit is to increase current for more power output. So maybe we have a current problem and the - side is overpowering the plus side. Remember, we have a problem on both channels so it has to be something that pertains to both sides. So looking at individual components that pertain to only 1 channel may not be the problem.
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nashou
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Post by nashou on Dec 5, 2016 21:17:12 GMT -5
Well it is my understanding that the servo circuit is to increase current for more power output. So maybe we have a current problem and the - side is overpowering the plus side. Remember, we have a problem on both channels so it has to be something that pertains to both sides. So looking at individual components that pertain to only 1 channel may not be the problem. ok, b ut before the problem was only on one channel then we did something to break the right channel. Or do you think that would have happened eventualy? So when I first turned it on and had the higher positive voltages on TR109 and 111 were they closer to where it needed to be? And I wonder if that happeed becuase of me removing R149 and 151 and if I put those back in Id get the same results of the voltage shift? So whats next? nashou |
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nashou
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Post by nashou on Dec 5, 2016 21:26:17 GMT -5
Also I timed the collapse. It started at 24.8 volts then droped to 23,9 after 1 minute then dropped to 11,89 at the 5 minute mark.
Nashou
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Post by mastertech on Dec 5, 2016 21:26:52 GMT -5
At this point I have no idea. Also remember you replaced tr119 and TR120, didn't you. And D105 I think was bad, on the - side. I am grasping here also. I am just thinking of something to try and disabling that circuit should not hurt anything that I can think of. It is up to you.
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nashou
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Post by nashou on Dec 5, 2016 21:42:53 GMT -5
Yeah that whole Circuit was replaced except the resistors in there .
I also replaced all the lytics on that board just to be safe.
I am almost inclined to remove every part and replace them lol.
I hate giving up but this is going to drive me nuts if I give up.
I wonder if there might be a bad solder joint that only acts up once it warms up.
Let me mess around some and then we'll try to remove the servo amp. I assume we
would remove R160 and 161 to do so?
Athanasios
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