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Post by kopraish on Apr 4, 2019 10:36:39 GMT -5
Service manual direct download: dox.abv.bg/download?id=44a915751cHi. I try to repair this amp from a long time. All four mosfet 2SK1529/2SJ200 was short, R521/621 and R520/R620 was open. At this moment i remove all final transistor 2SK1529/2SJ200 i put lmp 75watts all relay close contacts but here is anather problem. On Q509/510 and Q609/610 i have 45v on BEC. I remove Q509/510 and Q609/610 from mainboar, and now i have 45V only on BE, collectors are 0v. But on service manual on emitters i must have 2.4v.... I don't have any short on all elements. Can you tell me what can i try, please. Video clip: Attachments:
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Post by mastertech on Apr 4, 2019 17:42:37 GMT -5
It sounds to me like you are finding a problem with both channels still. If you need me to help you locate the problem I would have to start from scratch. Jumping in to where you are now would be like hunting for a needle. So this would mean I would need you to put all good parts back in and we can start testing from there.. Let me know what you want to do.
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Post by kopraish on Apr 4, 2019 19:16:57 GMT -5
Ok. I put everything back. All final and driver transistors are brand new. The lamp 75 watts light full, relays don't close contact.
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Post by mastertech on Apr 4, 2019 19:37:04 GMT -5
Ok. Go to ic700. DMM on DC volts, neg probe on pin 5 and test voltage on pins 1 and 2. EDIT: might as well test voltage on pins 6,7 and 8 also while you are there.  |
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Post by kopraish on Apr 5, 2019 0:29:35 GMT -5
1. 0v
2. -0.66v
6. 3.4v
7. 1v
8. 1.4v
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Post by mastertech on Apr 5, 2019 8:51:57 GMT -5
Interesting. Test pin 4 now. Also locate Q700 and give me the voltage on each leg. Then also locate R708 and give me voltage on each side of it.
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Post by kopraish on Apr 5, 2019 12:45:19 GMT -5
Pin 4 (upc1237ha) - 0.72v
Q700 - B-0V, E- +2.3V, C - +2.4V
R708 - (one side 2.7V, other side 3.0v)
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Post by mastertech on Apr 5, 2019 13:00:06 GMT -5
Pin 4 (upc1237ha) - 0.72v Q700 - B-0V, E- +2.3V, C - +2.4V R708 - (one side 2.7V, other side 3.0v) Yeah, they are all no good. Are you still running that light bulb and is it in F1 location? If so snap the fuse back in and check again. |
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Post by kopraish on Apr 5, 2019 13:16:05 GMT -5
Are mean to put back fuse? At this moment, when all components are connected (final, driver transistors are connected on main board) bulb light non-stop.
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Post by mastertech on Apr 5, 2019 13:23:48 GMT -5
Are mean to put back fuse? At this moment, when all components are connected (final, driver transistors are connected on main board) bulb light non-stop. So you are concerned that if you put the fuse back in it may damage some parts? The light bulb is in F1 on the power supply board, correct? Can you disconnect the wire harness CN751 on the power supply board? If yes then disconnect in and see if your light bulb goes out. |
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Post by kopraish on Apr 5, 2019 13:28:53 GMT -5
Yes, the light bulb is in F1 on the power supply board. I remove CN751, and bulb goes out.
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Post by mastertech on Apr 5, 2019 13:37:11 GMT -5
Yes, the light bulb is in F1 on the power supply board. I remove CN751, and bulb goes out. Ok, good. Leave that harness disconnected and put fuse F1 back in and go back and retest those voltages at ic700, Q701 and R708. |
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Post by kopraish on Apr 5, 2019 13:52:17 GMT -5
IC700 : 1/2/3/4 pins= 0V , 6pin - 0.39V, 7pin - 0.10v, 8pin - 0.10v
Q700 - B-0V, E- +0.10V, C- +0.10V
R708 -both sides 0.28v
These voltages are without CN751 with fuse.
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Post by mastertech on Apr 5, 2019 14:10:12 GMT -5
Do a diode test on the 3 circled diodes. If they test ok then test for AC voltage at the red arrow locations. Just put your 2 DMM probes across those 2 points. No need for a probe to ground.  |
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Post by kopraish on Apr 5, 2019 14:20:11 GMT -5
Diodes are fine. Between 1 and 3 i have 73.4v AC.
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