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Sansui AU-217 restore

Your welcome.

TupolevFan said:
Some notes regarding 2SA798. After experimenting with different adapters, it was still too time consuming to put all of those jumpers and bent legs and it looks a bit ugly, i decided to use easyEDA program and designed my own adapter with correct pinout and ordered 20 of them for the price of 15 USD ( this includes shipping) if i order 20 dual Nexperia chips for 0.40USD each + shipping i would get 1.50 per 2SA798 replacement
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This sounds like a good plan and should look very neat. Personally l just use KSA992 pairs for this purpose but with your adapters l like the idea of having the option of the 6TSOP packages.
 
Binkman said:
Got a diagram you can post up?
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I attached gerber file. Just noticed that P4 pin trace was oddly placed but it shouldn't matter. The pinout is symmetrical (as the original 2SA798. Also one can install the chip without worrying where the 1st leg is since the chip is also symmetric in that regard. i will post how it came out when i get actual adapter
 

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Here are the pics of the adapter
 

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g'day.. thanks for the pics, So what are you using for the solder leads? Hope you can show how they mount, too.
 
Binkman said:
g'day.. thanks for the pics, So what are you using for the solder leads? Hope you can show how they mount, too.
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To be honest I did not figure out yet anything better then regular wire 0.5, 0.6 mm (not sure exact gauge) . If anyone has better ideas i am opened for suggestions. However considering that original 2SA798 has similar leg thickness i can't think of any manufactured leads ( may be there are but i yet to find them).
 
I will not use my latest adapter with this current AU-217 because i already installed my ugly version of Nexperia chip + "clumsy" adapter :D. Just do not want to desolder it and risk another pulled trace ( I had enough of those already). I was trying to be careful but this time for some reasons i had a few traces which disconnected at the point of component soldering. And i do not think i overheated it. Possibly the board quality or age (it is nor FR4 type for sure). So had to reinforce those areas with thin wire imbedded into the solder and those look a bit ugly ( like an @ss.) but have reliable connections and steady.
 
TupolevFan said:
.... I usually use a stainless steel needle to clean the whole from the solder (briefly hitting it up and sticking the needle in and pulling it out). ...
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I use a wood toothpick. Solder doesn't adhere to wood. Many times it's not even needed, if you are handy with the soldering iron tip, you can clen the hole in a side movement.
 
Binkman said:
So have you finished the unit?
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I did finish recap and replacing all the components (bias pots, VD1212, fusistors) but i did not have time to put it back together (family time)
elnaldo said:
I use a wood toothpick. Solder doesn't adhere to wood. Many times it's not even needed, if you are handy with the soldering iron tip, you can clen the hole in a side movement.
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You are right that often it opens up without much effort, but i also had cases (my eyesite up close is not that good anymore) when it seemed there nothing in the whole but in fact there is tini tiny bump which is on the way of component leg and if i was stupid enough to apply a bit pressure than trace was lose and i hate myself if it happens :))
 
TupolevFan said:
You are right that often it opens up without much effort, but i also had cases (my eyesite up close is not that good anymore) when it seemed there nothing in the whole but in fact there is tini tiny bump which is on the way of component leg and if i was stupid enough to apply a bit pressure than trace was lose and i hate myself if it happens
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I wouldn't be so hard on yourself.. some traces and pads just suck and age doesn't help. (pcb age :D) I use magnifiers and take a good look all over first as well inspect initial soldering performed. Bent component leads need to be lifted, too and don't dwell on one solder point.. easy to do forgetting allow to cool or being in a rush. (i.e. I didn't get the solder off right away? so keep hitting it. habit.) I bought some stainless probes for clearing holes and other tasks. xacto knife is good for lifting bent leads, flush cutters for similar tasks
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Binkman said:
I wouldn't be so hard on yourself.. some traces and pads just suck and age doesn't help. (pcb age :D) I use magnifiers and take a good look all over first as well inspect initial soldering performed. Bent component leads need to be lifted, too and don't dwell on one solder point.. easy to do forgetting allow to cool or being in a rush. (i.e. I didn't get the solder off right away? so keep hitting it. habit.) I bought some stainless probes for clearing holes and other tasks. xacto knife is good for lifting bent leads, flush cutters for similar tasks
View attachment 1600902
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Your toolset painfully reminded me that my dentist visit is due :D:D (no offence just association). I have similar toolset.
After some debate with the "smart guy" (that is how my wife makes fun on me when i mumbling to my self : having conversation with a smart person?), I decided to use new adapters because old assembly was just too ugly. I desoldered old and installed new. (Pics bellow)
 

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Yes that does look better, more proportionate. (like it really matters with the cover on..) However, I can assure after about 6 yrs. as a member and a year or so lurking, 1st time I've seen this application on the forums both this and the SU-8600 and your neighbors SU-7600 Another SU-8600 rebuild. | Page 3 | Audiokarma Home Audio Stereo Discussion Forums

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-BTW if you're sane and talk to yourself, it's normal. Especially tech stuff.
 
Assembled the unit yesterday (not fully yet) . fired it up relay clicked. Adjusted bias to 7mv as per Service manual. DC offset is 0.5mv one channel and 2.2 mv another. Hooked up speakers and sound was out fine. Now the bad part. there is a audible noise when source is on the pause and it depends on the volume. if volume is at min no noise and max - then max noise. I connected my oscilloscope to the output and it seems that one channel is oscillating ???? I see sine wave around 50 kHz on the output and amplitude depends on the volume pot?? At max amplitude is around 1,5V. And it is not really clear sine wave i can not stabilize it very well on the screen of oscilloscope. Or is it just interference ? Another channel exhibits similar behaviour but the difference is that this sine wave is maximized when volume pot is in the middle and noting when pot is either at max or min. strange. I think i might have a ground issue. somewhere. When i change to the phono stage there is low frequency noise added ( 100HZ) and looks like sine wave as well. Also I did not notice it before but on Equalizer board somebody cut trace around tape monitor switch around pins which were connected to the ground. not sure why
 
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Also i realized that EMI shielding screen is missing over the board 2758. Also I will need to do a better job at cleaning input selector switch. Any suggestion about EMI shielding?
 
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