Recent content by jedlejedi

You can find some really useful info here (in Italian) http://www.introni.it/pdf/Selezione%20Radio%201962_03_04.pdf

I found the answer to my question here: http://audiokarma.org/forums/index.php?threads/leestereos-restoration-upgrade-of-a-sansui-au-555a.816754/ Thanks @Leestereo

Hi, I am recapping a Sansui AU 555A as well. There are a few caps on the PSU: 1 x 2200uF, 1 x 1000uF and 2x470uF. So it looks like a few people have upgraded the 2200uF to 4700uF. What about the other 3? Does it make sense to upgrade them as well?

Hi kwape, I am about to recap one one of those. I was wondering what kind of film cap you used for the 6.8uF bp cap in the tone control board? Cheers

AU-101,514052578,jedlejedi G-4700,820020626,jedlejedi

Ok, that's actually not right. I was measuring the bias incorrectly. It turns out that I can definitely get a bias of 20mA. At that level the amp seems to be performing fine.

Ok, John you were right! Embarrassingly I wasn't measuring the bias current across the fuses properly and my meter was giving me values that were 10x the actual current. I realized my mistake when measuring the voltage across the emitter resistors which gave me a much a more sensible value. It...

Thanks John and Tom You've got a point John, a faulty meter (or me making a mistake) would explain it. I just checked the meter by measuring the current in a simple circuit containing a 1.5V battery and the 8.2Ω resistor and it's giving me the result I expected (0.185A). So it looks like the...

Hi, I checked most of the resistors on the power amp board and the only one that seems to be out of tolerance is one of the emitter resistor on the right channel. I measured it at 0.7Ω instead on 0.5Ω not sure whether that could be the cause of the lower bias current on that channel. There are a...

Hi, I finally got around to checking VR901. When I move the slider all the way to one side it looks like the protection is kicking in and the bias current drops to 0.2mA. When I move it to the other side the bias current goes up to around 18mA on one side and 12mA on the other side. Not that I...

I had a similar issue on this amp. The problem was a dry solder for one resistor on the power amp board. Agree that it probably would be good to change the flying saucer transistors regardless. I had another issue with the bias current fluctuating a lot which got resolved when I replaced them.

Hi John, Yes, they seem to be, assuming the markings on the PCB board are correct. I didn't change any other transistors. The only other components that I changed were the electrolytic caps and the trim pots for the bias and output adjustments. Thanks, Julien

I did notice that the bias trimmers were 200Ω and the output adjustment ones 200KΩ. I doubled checked them today and the values are correct. I will check VR901 this weekend when I have a bit more time. Is there risk of damaging the out pout transistors if I set it to the wrong value? Pete, it...

Thanks. It's an AU-555. I can't really see any transistor mounted on the heat sink other than the output transistors unlike some of the other Sansui (e.g. AU 3900) I was planning on changing all the transistors on the amp board but I am really struggling to find suitable replacements. There...

AU-555,580012287,jedlejedi