nashou
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Post by nashou on Mar 16, 2019 19:44:01 GMT -5
Pull all those outputs and see if you still have DC on the speaker out lines. ok will do, the right one will be easy the left one will be harder to get screw driver in there. Also not sure if anyone else worked on this but the right outputs had no thermal paste on them!!! But it looks factory installed, like they forgot at assembly Ok pulled all 4 and still have DC on speaker outs, but only after relay clicks in . So if this has speaker protection its not working. thats IF it has it, might not. next? Nashou |
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Post by mastertech on Mar 16, 2019 19:49:25 GMT -5
1) How much DC on those lines?
2) Test voltage on each pin of socket of removed transistors. Check 1 amp and give me the 3 and 3 voltages. I do not need to know which pin is which, just voltage numbers. Then check other amp pins just to see if they are the same.
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nashou
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Post by nashou on Mar 16, 2019 19:56:27 GMT -5
1) How much DC on those lines? 2) Test voltage on each pin of socket of removed transistors. Check 1 amp and give me the 3 and 3 voltages. I do not need to know which pin is which, just voltage numbers. Then check other amp pins just to see if they are the same. 1) the speaker outs? Same as before. 2) working on it now ......... |
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Post by mastertech on Mar 16, 2019 20:02:42 GMT -5
Oh, so DC is the same on those speaker lines with or without the outputs, OK.
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nashou
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Post by nashou on Mar 16, 2019 20:07:42 GMT -5
1) How much DC on those lines? 2) Test voltage on each pin of socket of removed transistors. Check 1 amp and give me the 3 and 3 voltages. I do not need to know which pin is which, just voltage numbers. Then check other amp pins just to see if they are the same. 1) the speaker outs? Same as before. 2) working on it now ......... ok transistor left then right if the case is the drain then I know that number. Left transistor = .1mv top pin, 1.6 vdc bottom pin and drain was 30.6 volts Right transistor= 30.62 vdc top pin, 32.24 vdc bottom pin and 59.4 vdc drain both amps measured about the same. next?  |
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Post by mastertech on Mar 16, 2019 20:16:12 GMT -5
Are you sure none of those voltages are a negative?
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nashou
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Post by nashou on Mar 16, 2019 20:20:06 GMT -5
Are you sure none of those voltages are a negative? I'll double check |
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nashou
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Post by nashou on Mar 16, 2019 20:21:39 GMT -5
nope, all posative , is that wrong?
Nashou
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Post by mastertech on Mar 16, 2019 20:25:02 GMT -5
Well at this point I am not sure. You have a very odd amp there. What is its history. Did your friend buy it not working or was it working and then failed?
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nashou
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Post by nashou on Mar 16, 2019 20:31:26 GMT -5
Well at this point I am not sure. You have a very odd amp there. What is its history. Did your friend buy it not working or was it working and then failed? My friend has a record shop and gets equipment in and if there is something that needs a little work he sometimes asks me. This he said worked but needed the tuner string repaired. I got that sorted and decided to listen to it. thats when I discovered all the issues. He said the person who sold it to him for 20 bucks said it was working. in a sense it was but not well. pretty distorted from both channels the louder one( left) worse than the right channel. It seems well b built , but just no info on it anywhere. It be cool to fix it for him. Might be a sansui or pioneer clone. nashou |
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Post by mastertech on Mar 16, 2019 20:42:21 GMT -5
The big thing is that all those outputs are the same but also voltage problems. Most all amps do not have the same outputs and if it wasn't for my vague memory that I think years ago I did see one with the same I may not be remembering correctly. I have pulled some old amp schematics and thought I had one very similar to yours even with what looks like the same protection relay but it does not have 2 of the same outputs. there should be 1 pos and 1 neg output. And I thought you measuring those voltages would confirm that but they did not. But you could have a PS problem where the neg voltage has a problem but you still could not run those same 2 outputs. Now if someone was messing with that amp after it blew and put the wrong parts in there and then damaged the neg rail it is all possible. But you would have to trace back to the PS to see if that is the case. I am 80 to 90% sure those outputs are 2SD188. The schematics I found use 2sd388 which are the same just higher output wattage. But they are not all 4 the same. They use complimentary outputs for the neg side which most all amps do. So you would have to have 1 of those rare amps and that is if my memory is even correct on that because I have not been able to find a schematic where all 4 are the same. And I looked at a lot.
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nashou
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Post by nashou on Mar 16, 2019 20:50:00 GMT -5
WOW, thanks Mac. But what would cause DC on the speaker outs with no output transistors installed? And would an amp still be able to play with two of the same outputs if it was suppose to have two different ones? Maybe tomorrow, if it will help, I'll take voltages at all the points I can on the power supply board and you can maybe see if anything is amiss there. with out a schematic or the unit in front of you I can see how it be hard to diagnose . maybe just quit while I'm ahead and chalk this up as a learning experience of an odd ball amp. I seem to find the weird stuff with no schematics a lot  Nashou |
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Post by mastertech on Mar 16, 2019 21:02:13 GMT -5
There are transistors in the amp section before those outputs that are also complimentary and if the neg line was down it would push some positive. Maybe on 1 of those amps pull the heatsinks off those 3 small transistors and see if you can get some numbers off of them. That may shed some light on things. I will also attach a schematic i have been looking at that I thought was similar to yours so you can see what i am talking about. But until some more things are confirmed I really don't know where we are at yet. But I am sure we can probably figure it out it you wanted to waste the time, LOL.  |
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nashou
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Post by nashou on Mar 16, 2019 21:10:29 GMT -5
There are transistors in the amp section before those outputs that are also complimentary and if the neg line was down it would push some positive. Maybe on 1 of those amps pull the heatsinks off those 3 small transistors and see if you can get some numbers off of them. That may shed some light on things. I will also attach a schematic i have been looking at that I thought was similar to yours so you can see what i am talking about. But until some more things are confirmed I really don't know where we are at yet. But I am sure we can probably figure it out it you wanted to waste the time, LOL. 2 NEC C853 M37 1 NEC A545 L34 And 1 NEC A640 M34 not on heat sink |
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Post by mastertech on Mar 16, 2019 21:13:12 GMT -5
You know, in thinking about this some more these may be Class A amps and 1 of those 188's on each channel may be a type of regulator. So we may just have to find out where that DC is coming from that is there now. I will look into this some more tomorrow.
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