Sansui AU217 in protection after touching chassis

[kotli79]

Hi,
I have finished fixing broken Sansui au 217 and also recapped it after fix it. Now it does work almost ok. The trouble is that it goes to protection when I am touching with hand metal parts/frame. Initially I thought that I am crazy with random protection mode. Do you recall any thread that would be talking about similar issue or have an idea how to troubleshoot it?

 

[Sui-Yogi]

Hi,
I have finished fixing broken Sansui au 217 and also recapped it after fix it. Now it does work almost ok. The trouble is that it goes to protection when I am touching with hand metal parts/frame. Initially I thought that I am crazy with random protection mode. Do you recall any thread that would be talking about similar issue or have an idea how to troubleshoot

leaking AC to the chassis ?
You need to check this , do you know how ?And be careful!!!!
You can easily get from been supposenly“crazy” , permanently dead .

This is not a joke situation…… be careful

 

[Hyperion]

Your symptoms may suggest a live chassis? - check all the ground connections are clean and tight. Sometimes washed off flux can get under a chassis ground tag and cause it to be disconnected, or simply left untightened after work.

You should measure zero voltage between any ground connection and the chassis, check with your meter on AC and on DC.

 

[Sui-Yogi]

Correct me if I’m wrong but first he needs to check live voltage on the chassis :

Black probe to the ground of the wall socket and red probe to the chassis …”AC mode on the multimeter ”

 

[whoaru99]

There is some amount of chassis to ground voltage where the leakage current is within safety standards. But, has to be measured correctly to ascertain that, not just a straight chassis to ground test.

 

[kotli79]

Thank you for 1st reactions and safety warning. I have started with checking connections and cleaning flux. Could it be something with the input terminal? I found it when connecting aux to source.

 

[kotli79]

There is some amount of chassis to ground voltage where the leakage current is within safety standards. But, has to be measured correctly to ascertain that, not just a straight chassis to ground test.

What is the correct way?

 

[whoaru99]

This type of arrangement is found in the service manual of some units.

Leakage is typically given in milliamps, and 0.5mA max is also found in the service manual of some units. Since the test is actually a voltage measurement across the network you can use the max current (0.5mA or something less if you choose) and use Ohm's Law to solve for the voltage reading. It's an AC RMS voltage reading.

 

[kotli79]

This type of arrangement is found in the service manual of some units.

Leakage is typically given in milliamps, and 0.5mA max is also found in the service manual of some units. Since the test is actually a voltage measurement across the network you can use the max current (0.5mA or something less if you choose) and use Ohm's Law to solve for the voltage reading. It's an AC RMS voltage reading.

View attachment 3365666

thank you. Reversing the power plug resolves the issue... Let's if I can measure it and find the issue since there are not too many cables on AC. Switch?

 

[whoaru99]

Schematic?

Sometimes there are resistor(s) and or capacitor(s) from the mains wire(s) to chassis.

Check all that.

 

[kotli79]

Schematic?

Sometimes there are resistor(s) and or capacitor(s) from the mains wire(s) to chassis.

Check all that.

I think magic happens between switch and chassis. I took switch off and there was 0,7A between switch and chassis. When flipping plug it reads 0A. I have bent the cover of the switch and spray it with contact cleaner. It dropped to 0,18A. Switch was quite greasy. Is it possible that rubberish cover around 0,01uF(150V) cap is conductive (?)

 

[Sui-Yogi]

0,01uF(150V)

Safety capacitors are pretty low cost , maybe considering replacing it anyways ?

 

[kotli79]

And goes to 2A (AC) when pressing on it when engaged

 

[kotli79]

Safety capacitors are pretty low cost , maybe considering replacing it anyways ?

I don’t have it on stock and it measures ok. What is strange is the switch that gives almost 2A to the chasis when pressing harder in ‘ON’ position

 

[Sui-Yogi]

I don’t have it on stock and it measures ok. What is strange is the switch that gives almost 2A to the chasis when pressing harder in ‘ON’ position

Do you think you can disassemble the switch and reassemble it safely ? Beware that is no replacement for this ( that I know of ) .
There is a possibility that AC spikes on “turn on” has deform the contacts and are getting in contact with cover of the switch.
If you open it up , you might be able to clean it and scrap the deformation or even make new contacts from bare metal … you possibly gonna need a Dremel for that.

Just a suggestion, I have never done it my self .

 

[kotli79]

Do you think you can disassemble the switch and reassemble it safely ? Beware that is no replacement for this ( that I know of ) .
There is a possibility that AC spikes on “turn on” has deform the contacts and are getting in contact with cover of the switch.
If you open it up , you might be able to clean it and scrap the deformation or even make new contacts from bare metal … you possibly gonna need a Dremel for that.

Just a suggestion, I have never done it my self .

It doesn’t look like it is possible to open it. It still has 2nd unused pair. Perhaps it is still usable. I was considering to put it into ultrasonic bath to wash off grease that comes out of it (?) replacement not easy to find

 

[Sui-Yogi]

It doesn’t look like it is possible to open it. It still has 2nd unused pair. Perhaps it is still usable. I was considering to put it into ultrasonic bath to wash off grease that comes out of it (?) replacement not easy to find

I’m not aware how the switch looks like on the AU-217( picture above does not show enough) , I do have an AU-517/717 and as far as I remember (if ever needed) I could see that it was possible .
If it has a second unused side , first see that it’s acctuly fitted with contacts and is working as a switch on that side .
If it works like a switch , I would move the wires to the unused side and performed the tests again , see what you get .
If everything is normal on the unused side , then the problem is to the contacts and ultra sound won’t do much , to my understanding how it works .
Imagine that in the switch will be pieces of black corroded metal “bumping around loose” …. Do you hear any tickling sound if you shake the switch ?

 

[kotli79]

I have pulled switch apart. It is easy to put it back. There is nothing inside that could cause trouble. It was ok when disassembled so I installed it and turned it on. Sadly same story touching chassis puts it in protection. Next day tried again and surprise no issue but then it slowly came back. I measured AC voltage between chassis and known ground = 163V. At that moment i gave up. Today I have removed power transformer and started to measure- I am getting 53-63V AC on the chassis of power transformer (negative from power socket) and about 23-44V AC on chassis. I did check power cord and it is ok. How to check if power transformer is ok or faulty? I hope it is not…

 

[kotli79]

I played a bit more and opened power transformer it is a bit brownish inside on the coils. When transformer is outside of chassis sansui works and has less than 1V AC on the chassis.
Now looking for donor and if anyone has tips for place within EU for parts. I know that financially it is likely not worth it but this was my 2nd project ;-)
thank you all for giving suggestions and warnings.

 

[kotli79]

Schematic?

Sometimes there are resistor(s) and or capacitor(s) from the mains wire(s) to chassis.

Check all that.

I did check again and with help of glasses found that indeed one of the caps that are connected to neutral in protection circuit was not properly soldered. So now regardless of the direction of socket I don’t have any issues. Just for sake of safety au217 has now a cable with ground.

What a learning point and thank you all support!!!