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Sansui AU-5500...terrible distortion from both speakers.

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pcrosewood

Active Member
Hello everyone.
I've been spending some of my housebound time getting my Sansui AU-5500 up and running. When I received it, The relay wouldn't click on and a few of the fuses where blown. Over time I replaced open transistors, a couple scorched resisters, and most of the caps on the driver and power supply board. Also recapped the tone control board. Checked all the circuit solder and redid any suspicious looking solders. Also replaced the relay. I'm to the point where I can get sound out both speakers but it is horribly distorted. Might mention also I need to turn volume up quite high to get the sound out but then can turn it down and still get sound. This happens on all settings...phono, aux, tuner.etc.When I use the 5500 as a pre amp, it works great. Using another preamp and the 5500 is terribly distorted. So, the pre is good, the main isn't.
Any guidance or suggestions would be greatly appreciated.
 
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First off, thanks for the response. Things have changed a bit since I posted this. I was able to set the bias and offset on the left channel but not the right. I did get rid of the distortion. Now, when I turn the amp on, R38 on the board smokes and burns. Also, one of the output transistors, R24, gets very hot and fuse #2 opens.
 
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Check the transistors for the right channel. sounds like some are shorted R24 is a half watt 100 ohm.. will also need replacing.
 
I checked and replaced all the transistors on the right channel and they are all good. Actually, I tested all the resistors, transistors and recapped the right channel and all are good I made a mistake and meant to write TR24 and not R24 in my last post.
 
Check your work. Check transistors are fitted correctly, remember modern replacements often have a different pinout from the original.Check cap polarity and diodes too.
 
On board F-2907B, I replaced all the caps and all the transistors except TR 23,24,25,26 and I replaced R36 and R38 resistors. On board F-2414, I replaced the caps and the TSC1313 transistors.
 
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Theres got to be a short somewhere.. How about the o/p transistors insulation pads. Check for any solder points that may be connected by excess solder etc.When i recently refurbed my Au-7700 i Put 2 Transistors in the wrong way round.Took ages to fault find that.
 
I was very concerned about putting transistors in wrong and so was very mindful of any changes I made. I went back over them several times to make sure. I will go and remove the o/p transistors and remount them to make sure no shorts there. I did remove them to test and all tested good. You're right, there's got to be a short somewhere.
 
I just removed all the o/p transistors and checked them again and all tested good. Cleaned old thermal paste off and re-pasted them and installed them. Put it on the bulb tester and it shows a short. Then R38 started to cook and smoke. I took photos but my computer can't detect new photos from my phone. I'll get some when I figure this out but won't be till tomorrow now. There is a photo on post #2 of the o/p transistors and the board. I want so bad to get this amp working.
 
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