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Post by mastertech on Mar 21, 2019 19:06:42 GMT -5
I looked at a bunch of different schematics but of similar design and I am seeing .5 watt resistors and not big value, like 100 ohm, 47 ohm sometimes a mylar cap, sometimes not. But here is what I am thinking. After cards and card slots are all cleaned up, change pots if possible, resolder 220 resistors on relay board, monitor voltage at speaker connectors and see if adjusting pots slightly will remove DC and see if heatsinks stay cool, maybe check bias voltage after that also just to see.
If still does not work right we can then see about adding more resistors and cap maybe.
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nashou
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Post by nashou on Mar 21, 2019 19:26:09 GMT -5
Ok, these pots are 520 ohm , I have 100 ohm and 1k pots .
I also found two 3 watt 500 ohm resistors . I might be able to swap out the 220 ohm's on the relay board .
I also just swapped out one 2sc853 from o e board to the other . Just because.
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nashou
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Post by nashou on Mar 21, 2019 19:56:21 GMT -5
well that was almost a disaster!!! The trimpot i used wasn't enough to adjust and i was the board begin to smoke so I shut it down. the emitter resistors got really hot.
the horizontal one read 0 ohms but now that it cooled its reading ok. Not sure if I should continue to use it. I am going to put the old trimmer back on and make sure its ok
again. man that was scary!!!
Cross your fingers.
Outputs seem ok.
nashou
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nashou
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Post by nashou on Mar 21, 2019 20:26:54 GMT -5
ok everything is ok with old pot back in. Wheeeooiouuuuuuu!!!!
What is an acceptable heat I should shoot for. When I go to lower the DC the heat goes up as well as the bias voltage.
If i lower the Bias voltage across the emitter resistor to the 5 mV's you suggested then the DC goes to 5 with the one board
and 3.4 with the other board.
I also think the smoke might have been some excess cleaner/lubricant fluid burning off.
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Post by mastertech on Mar 21, 2019 20:32:00 GMT -5
If i lower the Bias voltage across the emitter resistor to the 5 mV's you suggested then the DC goes to 5 with the one board and 3.4 with the other board. It is still doing this now or are you just referencing from before? |
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nashou
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Post by nashou on Mar 21, 2019 20:33:30 GMT -5
If i lower the Bias voltage across the emitter resistor to the 5 mV's you suggested then the DC goes to 5 with the one board and 3.4 with the other board. It is still doing this now or are you just referencing from before? Still doing it now, same as before.  |
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nashou
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Post by nashou on Mar 21, 2019 20:53:11 GMT -5
I looked at a bunch of different schematics but of similar design and I am seeing .5 watt resistors and not big value, like 100 ohm, 47 ohm sometimes a mylar cap, sometimes not. But here is what I am thinking. After cards and card slots are all cleaned up, change pots if possible, resolder 220 resistors on relay board, monitor voltage at speaker connectors and see if adjusting pots slightly will remove DC and see if heatsinks stay cool, maybe check bias voltage after that also just to see. If still does not work right we can then see about adding more resistors and cap maybe. Is this what you mean with the resistor and cap? I have also seen the resistor and inductor used here as well. But this is in series not to GND I think what is that for?  |
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Post by mastertech on Mar 21, 2019 21:23:59 GMT -5
Yes, those are all dc filtering.
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Post by mastertech on Mar 21, 2019 21:33:58 GMT -5
I'm going to be signing off for the night soon so if you wanted to try just the resistor and cap Put it after the cap there now. You could solder right on the neg leg of your filer cap and then to gnd. Do the 10ohm/.5watt resistor and the cap should be around .047uf/50mw mylar if you have one.
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nashou
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Post by nashou on Mar 22, 2019 7:23:55 GMT -5
I'm going to be signing off for the night soon so if you wanted to try just the resistor and cap Put it after the cap there now. You could solder right on the neg leg of your filer cap and then to gnd. Do the 10ohm/.5watt resistor and the cap should be around .047uf/50mw mylar if you have one. Sounds like a plan. But what If i first try increasing the 220 ohm resistors on the relay board with those 3 watt 500 ohm Ohmite resistors I have first? today is one of my long days here at The Odyssey so wont be home till about 8pm to try. nashou |
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Post by mastertech on Mar 22, 2019 10:30:33 GMT -5
Try what ever you like. This is all experimental. Should be no harm with any of these options.
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nashou
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Post by nashou on Mar 22, 2019 20:10:11 GMT -5
Try what ever you like. This is all experimental. Should be no harm with any of these options. Ok I tried your idea , 10 ohm and a .047uf cap ( all I have are Wima film ) and DC went down maybe a 1 to 1/2 VDC at speaker outs. So it helped a little . Also this time the voltage at the Neg Cap leg is equal to voltage at speaker outs . Before it was much higher I think , like 6 volts at neg cap leg . So it went down a bit. What needs to increase ? the resistor or cap value? Or should I try those 500 ohm 3 watt ceramic Ohmite resistors I have on the relay board This side was up to 5.xx vdc now its lower  |
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nashou
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Post by nashou on Mar 22, 2019 20:17:04 GMT -5
Another thing I noticed is the two red AC detecting lights on my DMM no longer light up when close to the chassis as before.
Before they would always be on unless i touched the chassis. So something is fixed on that front.
Nashou
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Post by mastertech on Mar 22, 2019 20:39:10 GMT -5
You can try the 500 ohm ones but the DC may go up instead of down. But see what happens.
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nashou
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Post by nashou on Mar 22, 2019 20:41:46 GMT -5
You can try the 500 ohm ones but the DC may go up instead of down. But see what happens. Why would it go up? |
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