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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Fri Jan 23, 2015 5:47 am Post subject: |
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well mac, seems like i am creating a bigger problem than what i started with. When i discovered the lifted pad on Q421, it was C but as i moved the board around soldering a jumper, now E and B are lifted as well. The problem comes from the heat sink that has to lay down while the transistors are installed and then folded back 90 degrees to attach to the amp board, bending the transistor leads. I was as careful as i could be but i apparently did not have the right amount of bend in the leads causing them to pull the pads away from the board. my problem now is that now that i have the pads jumpered, the pads themselves are not even connected to the board. should i try to epoxy them or crazy glue the pads back to the board or just left them as they are?
P.S. I think I see where i may have made my mistake. I zoomed in on the diagram of the amp board and now I see that the slots that the transistor leads fit in are just slots in the board, they also have a little notch in the bottom to catch the lead and hold it in so that all the pressure is not placed on the solder joints. tomorrow i will see what i can do to correct this mistake. but i still don't know how to deal with the pads that are completely lifted from the board, so i would appreciate your thoughts.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Jan 23, 2015 6:25 pm Post subject: |
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If the traces are damaged beyond getting a good, solid connection you can use wire to connect each leg to the next closest solder connection point.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Fri Jan 23, 2015 7:34 pm Post subject: |
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okay that is what i am working on doing now
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Sun Jan 25, 2015 8:45 pm Post subject: |
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Hi mac....I have all the transistor pins connected back to the amp board. I now have good volume out of the right channel but the distortion is there all the way from low to high volume levels. Could it be one of the resistors that i replaced?
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Sun Jan 25, 2015 8:50 pm Post subject: |
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R458, R467, R468, R483, R474, R475, or possibly the caps that i did not replace , C417, C430?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 26, 2015 3:55 pm Post subject: |
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Distortion is most likely a cap.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Mon Jan 26, 2015 8:50 pm Post subject: |
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Okay, should i check the caps off of Q416 or Q422? Should I check the surface mount caps like C417 and C430 or the large electrolytics like C420 and C423?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 26, 2015 9:52 pm Post subject: |
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How are you going to check them?
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Mon Jan 26, 2015 10:19 pm Post subject: |
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with my DMM
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Mon Jan 26, 2015 10:20 pm Post subject: |
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and my cap analyzer
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Mon Jan 26, 2015 10:21 pm Post subject: |
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i have an ESR tester for the electrolytics
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 26, 2015 10:45 pm Post subject: |
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Then start here:
C424
C423
C420
C530
C531
C419
If you don't find it here then we are back to where we will need to know if the problem is in the amp section or the preamp section.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Mon Jan 26, 2015 10:48 pm Post subject: |
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Ok I will check those first
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Tue Jan 27, 2015 9:04 pm Post subject: |
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okay mac, all the caps tested good on my esr meter. I was surely hoping to locate a bad one because I have all on hand except C419 100uf 100v. I did replace C426 because it had bulged on top. so i will install the board and check the headphone again.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Tue Jan 27, 2015 9:33 pm Post subject: |
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okay mac, good sound from left and right of headphones. Right channel output sounds a lot like a blown speaker, but the same speaker plays fine on the Left channel.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Tue Jan 27, 2015 10:51 pm Post subject: |
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The remote control came in today.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Jan 27, 2015 11:04 pm Post subject: |
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Well since the volume is now normal you know it is not a menu adjustment.
At this point in order to find the problem it would help doing a signal trace. But it would be nice to be sure if the problem is in the amp section or the preamp section. This is where swapping the preamp wire would help. But you did not want to do that the last time I suggested it. So then it would be a signal trace. Do you have another working receiver?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Jan 27, 2015 11:05 pm Post subject: |
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Another thought is, maybe check the idle current just to be sure it is not way out of whack.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Tue Jan 27, 2015 11:18 pm Post subject: |
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Wouldn't good sound out of left and right head phones indicate that the pre-amp section is good? No I don't have another receiver. I do have a stereo pre-amp. I also have a separate stereo amp, but I is not working at the moment.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Jan 27, 2015 11:33 pm Post subject: |
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| jgrice53 wrote: | | Wouldn't good sound out of left and right head phones indicate that the pre-amp section is good?. |
I am not sure why you think the head phone jack comes directly from the preamp section. That is why I posted that schematic a while back and asked if you could read schematics at least a little. The head phone jack is wired in after the amp section just like the A and B speakers output connectors. Relays merely switch on or off.
I thought that maybe when the headphone was plugged in that the DSP section might of been bypassing and sending a pure direct signal through, thus giving you a (what you think) normal sound from the head phones.
That is what I had you disconnect the full amp channel lines and you soldered a wire to the FR output. You had the distortion. I then said plug in the head phone anyways. And you won't hear anything from the head phones. You still had the distortion on the speaker. If the DSP was changing the signal back there then it would of made a difference in the output sound. It did not.
So your headphones are somehow filtering out the distortion. Could just be because of the load difference on the amp.
Anyways, there are very few ways to trace down a distortion. Since you don't have another receiver to use as a testing device then the next thing would be to swap those preamp lines. You have to at least narrow down the location of the problem part or it could be hundreds of different components.
Did you check the idle current on that FR channel yet?
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