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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Tue Jan 27, 2015 11:46 pm Post subject: |
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i don't know how to check the idle current. and at this point i will swap the wires. how would i use another receiver to test?
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 12:16 am Post subject: |
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the only experience i have troubleshooting receivers is from many years ago, and only a couple at that. and I always thought that the headphones came from the pre-amp section. that is how i determined what section to troubleshoot. A good clean signal from the headphones meant a problem in the amp section, noise or no sound or sound on only side of the headphones meant the problem was in the pre-amp section. have i always been wrong or are modern receivers different?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Jan 28, 2015 12:19 am Post subject: |
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To check idle current look on the amp board for the white plastic connectors. See red circle below. Nothing connected to receiver. Turn on. Set DMM on DC voltage and test 2 outer pins. Voltage should be 2.0mV. If not, adjust trim pot, blue circle.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 2:26 pm Post subject: |
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when i connect my DMM to the 2 outer pins on FR_TP402 i get 0.0mv and adjusting the pot FR_VR402 has no effect on the reading. I turned the pot slowly through its entire range and the DMM did not change at all.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Jan 28, 2015 2:51 pm Post subject: |
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Did you try on a different channel to verify your meter and process?
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 3:09 pm Post subject: |
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no i only connected the probes and powered on the receiver, waited for 1 minuted and observed the meter. i did reverse the leads but that made no difference either. i don't have any input and no speaker connected. are you saying to select speaker A and then Speaker B?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Jan 28, 2015 3:46 pm Post subject: |
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No, I am saying to try another test point (TP405,or 03 or 02, 01) and see if you get a correct reading.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 3:51 pm Post subject: |
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I switched from speaker A to B and no difference
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 4:00 pm Post subject: |
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oh okay i will try that
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 4:26 pm Post subject: |
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TP405 2.5mv
TP403 2.0mv
TP401 2.5mv
TP402 0.0mv
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Jan 28, 2015 5:59 pm Post subject: |
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I see i typed 402 instead of 404 but it is probably fine. So we now have something going on there. On my way out now so when I get back i will look over the schematics. If anyone else wants to chime in while I am gone here is the schematic for that channel.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Jan 28, 2015 8:57 pm Post subject: |
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I would start by lifting 1 end of R476 and R479, value test each of those and then test VR402. Make sure VR402 works properly. If all ok then remove Q421 and carefully test it.
Verify that R465,R477,R463,C427,C499 are unpopulated.
If still ok then recheck D409,D410,ZD405 and ZD406.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Wed Jan 28, 2015 9:07 pm Post subject: |
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okay mac i will get started on that.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Thu Jan 29, 2015 12:20 am Post subject: |
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how do i verify that these components are not populated? i don't know what that means mac.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jan 29, 2015 1:07 am Post subject: |
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Oh, lol. That's means they are not there. There is a place for a component but nothing was placed in that location. So I am saying, find the spot where it should be by the number I gave and verify there is no component in that location.
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Thu Jan 29, 2015 6:26 am Post subject: |
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R476 2.64 kohm 1 leg lifted
R479 553 ohm 1 leg lifted
VR402 good---checked with test probes on 2 of the pins and turned the pot while monitoring the DMM readings and the ohms increased and decreased as I turned the pot.
Q421 good
verified unpopulated R465, R477, R463, C427, C499
D409, D410, ZD405, ZD406 good
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jan 29, 2015 2:52 pm Post subject: |
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Did you check the value across that pot?
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Thu Jan 29, 2015 3:02 pm Post subject: |
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yes, 197ohms
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jgrice53
Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571
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| Posted: Thu Jan 29, 2015 3:08 pm Post subject: |
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across the 2 outer pins of TP402 is 19.6k ohms
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jan 29, 2015 3:43 pm Post subject: |
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| jgrice53 wrote: | | across the 2 outer pins of TP402 is 19.6k ohms |
I do not think that value is correct. Check some of the other pots and see what they read.
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