nashou
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Post by nashou on Feb 16, 2017 23:03:10 GMT -5
The schematic shows a R9020 (10k) connected directly to R9010 (1k). Its on the underside. |
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Post by mastertech on Feb 16, 2017 23:09:40 GMT -5
Ok, here is the thing. I think that it is probably ok since you had 3.3v on Q702. But you should of also had voltage on one side of R9010 since they are connected. If you do a continuity test between the 2 resistors you should have continuity between them on 1 side each. I would suspect that maybe on R9010 the solder joint is cracked and it is not making contact with the trace between the 2 or there is a problem with the trace. I will let you investigate.
Gotta go for today. I will check back tomorrow and see how you make out.
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nashou
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Post by nashou on Feb 17, 2017 8:56:57 GMT -5
Ok, here is the thing. I think that it is probably ok since you had 3.3v on Q702. But you should of also had voltage on one side of R9010 since they are connected. If you do a continuity test between the 2 resistors you should have continuity between them on 1 side each. I would suspect that maybe on R9010 the solder joint is cracked and it is not making contact with the trace between the 2 or there is a problem with the trace. I will let you investigate. Gotta go for today. I will check back tomorrow and see how you make out. I have continuity on one side of the resistors , it was a pain trying to keep the probe on one side not being able to see what you doing while probing the other side !!! Ugh but there is a connection. There are a bunch if 3.3 voltage generators all over this amp , are we looking at the correct one that is causing a low voltage at some points I did notice some corrosion I missed before around IC73 , cleaned it up and the amp almost turned on. I saw the display light up fully. But there is another aspect to this. I used compressed air to blow away areas I cleaned and the board got really cold before turn on. Maybe there is a heat related issue but I doubt it, just thinking out loud. Also pressing one of the four larger buttons on the amp face plate makes other relays click . I'll down load the schematics here at work and do some more research. nashou |
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Post by mastertech on Feb 17, 2017 11:12:21 GMT -5
Well according to the schematic the same trace that connects these 2 resistors is the same trace that goes to Q702 where you said you measured 3.3v
So why do you have 3.3v there but not on one side of R9010? How good was you continuity between the 2 resistors? I was hoping maybe you had a bad through hole in the trace since the resistors are on opposite sides of the board. But you would need to get a voltage measurement on both sides of R9020
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nashou
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Post by nashou on Feb 17, 2017 20:07:58 GMT -5
Well according to the schematic the same trace that connects these 2 resistors is the same trace that goes to Q702 where you said you measured 3.3v So why do you have 3.3v there but not on one side of R9010? How good was you continuity between the 2 resistors? I was hoping maybe you had a bad through hole in the trace since the resistors are on opposite sides of the board. But you would need to get a voltage measurement on both sides of R9020 Ok figured out how to put board vertical so I could very carefully get the voltage and take an ohm reading of R9020 I got the 3.3 on one side but 20mV on the other side where as r9023 had the 3.3 on both sides . Also the ohms reading is off it should be 10k but was only 3.4k . not sure if that reading is from another part of the board. I think its a 404 part size . Have to see what I have in 804 size I know I have some some where. Whats next? I also noticed weird reading on the line of transistors Q9013-9019 some are suppose to be negative but I only have one negative at q9015 but its -6.8 . but i assume that will come at a later time once we figure out r9020. Nashou |
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Post by mastertech on Feb 17, 2017 20:25:53 GMT -5
I still do not understand why you don't have 3.3v on both sides of R9020 since you have 3.3v on Q702. Remove Q702 and see if you have 3.3v on both sides of R9020.
Do you have continuity between Q702 and R9020?
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nashou
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Post by nashou on Feb 17, 2017 20:43:46 GMT -5
Ok, the 3.3 voltage I have on Q702 is on pin 2, the input . And the continuity , with 702 installed , is from pin 3( the output ) to one side of R9020, the side away from the HDMI inputs on the board layout diagram.
Should I still remove Q702 ?
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Post by mastertech on Feb 17, 2017 20:56:59 GMT -5
Crap. I just realized something. When you did your voltage testing on Q702 you did not indicate which leg you were getting the 3.3v on.
Was it on the base?
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nashou
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Post by nashou on Feb 17, 2017 20:59:01 GMT -5
Crap. I just realized something. When you did your voltage testing on Q702 you did not indicate which leg you were getting the 3.3v on. Was it on the base? on the input pin I got 3.2 but it should be 1.2  |
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Post by mastertech on Feb 17, 2017 21:02:47 GMT -5
I dont know why they are calling those pins in and out cause it is not a regulator. it is just a switch. And the in is base.
Anyways the switch is being turned on by an HDMI problem. How difficult is it to remove Q702 without damaging it?
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nashou
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Post by nashou on Feb 17, 2017 21:09:06 GMT -5
I dont know why they are calling those pins in and out cause it is not a regulator. it is just a switch. And the in is base. Anyways the switch is being turned on by an HDMI problem. How difficult is it to remove Q702 without damaging it? Not a problem I have a hot air station . here is the data sheet for it. I think I posted it before. the part has biasing resistors built into it . www.alliedelec.com/m/d/fb22d391cbd5421fdec99d08875c5082.pdfTo get to the bottom of the board I had to remove the one Ribon cable from the front HDMI port . But I had those voltages also before i tilted the board to get to the bottom. Wanting to learn here....how did you realize it is being turned on from an HDMI issue? I'll remove while you answer. Nashou |
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nashou
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Tech in Training.....
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Post by nashou on Feb 17, 2017 21:24:29 GMT -5
Ok part is removed and tested good in my tester.
Next step
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Post by mastertech on Feb 17, 2017 21:30:09 GMT -5
If you look at the schematic of Q702 on page 116 of the SM you can see that the base voltage should be 0v. But you have 3.3v which then turns it on and when on, it shorts the collector line to ground. This is why the PS1_PRT line is 0v. It is being shorted to ground which is why you had 0v at pin 2 of ic901 which is then why pin 3 of ic901 is low which is connected to CPU pin 135, which should be 1.1v
So if you remove Q702 and the voltages become normal we can then continue and troubleshoot what is turning on Q702. And Q702 monitors the regulators for the voltages of part of the HDMI section.
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Post by mastertech on Feb 17, 2017 21:30:53 GMT -5
Ok, go back and check voltages at pins 2 and 3 of ic901.
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nashou
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Post by nashou on Feb 17, 2017 21:34:19 GMT -5
If you look at the schematic of Q702 on page 116 of the SM you can see that the base voltage should be 0v. But you have 3.3v which then turns it on and when on, it shorts the collector line to ground. This is why the PS1_PRT line is 0v. It is being shorted to ground which is why you had 0v at pin 2 of ic901 which is then why pin 3 of ic901 is low which is connected to CPU pin 135, which should be 1.1v So if you remove Q702 and the voltages become normal we can then continue and troubleshoot what is turning on Q702. And Q702 monitors the regulators for the voltages of part of the HDMI section. Thanks Mac., Just realized I was able to test voltages on the underside while the board was disconnected from the vertical board on the right side of the unit. Not sure what board it is. So now I should power up and test voltages on ic901? Nashou |
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