Bits are burning in my JA-S11 Amp

[xxxxxxxxxxxxxx]

Yes, again this is about my JA-S11 JVC Amp like in my previos thread. Now I was trying to repair it, and I was going to test the output pins on the Sanken s-40w, but before I could, resistor 629 started to release the magic smoke.
Also the nearby transistor, a 2SB560, gets pretty warm too.

This is all in the attachment called schematic. I've circled the smoking resistor and warming transistor. I've also included a photo with the same parts circled, but the schematic should be of most help. The full service manual, including a PCB layout, is available here. (Note: You may need an account to view it - the account is worth it, though (free))

Okay, so obviously the amp is stereo, one chanel has a fault, so lets look at the component pairs. I tested all the main parts of each of the chanels (in the faulty area only) and found that the problem chanel's values matched the OK chanel - so I assume there is probably not a fault here.

What I do believe, though is that the problematic chanel's darlington chipset (a SanKen S-40, shematic included) is at cause. The problematic chaels S-40W was also the one that heated up a lot (with no input) like I described in my previous thread.

I have found a seller of S-40W's but I want to be sure, as, well, they're expensive


Thanks a lot

 

[Nigel Goodwin]

Remove the offending chip, and check carefully all other components in the faulty channel - anything in the DC loop could cause the output IC to fail again.

But the smoking resistor may just be down to the chip.

 

[xxxxxxxxxxxxxx]

Thanks Nigel. Please excuse my noobiness, but what is the DC loop here? Is that the feedback circuit?

So I should buy a new chip then...

 

[Nigel Goodwin]

Thanks Nigel. Please excuse my noobiness, but what is the DC loop here? Is that the feedback circuit?

Everything between C603 and F601.

So I should buy a new chip then...

Yes.

 

[stingniki]

Yes, again this is about my JA-S11 JVC Amp like in my previos thread. Now I was trying to repair it, and I was going to test the output pins on the Sanken s-40w, but before I could, resistor 629 started to release the magic smoke.
Also the nearby transistor, a 2SB560, gets pretty warm too.

This is all in the attachment called schematic. I've circled the smoking resistor and warming transistor. I've also included a photo with the same parts circled, but the schematic should be of most help. The full service manual, including a PCB layout, is available here. (Note: You may need an account to view it - the account is worth it, though (free))

Okay, so obviously the amp is stereo, one chanel has a fault, so lets look at the component pairs. I tested all the main parts of each of the chanels (in the faulty area only) and found that the problem chanel's values matched the OK chanel - so I assume there is probably not a fault here.

What I do believe, though is that the problematic chanel's darlington chipset (a SanKen S-40, shematic included) is at cause. The problematic chaels S-40W was also the one that heated up a lot (with no input) like I described in my previous thread.

I have found a seller of S-40W's but I want to be sure, as, well, they're expensive


Thanks a lot

Hi, where did you find the electronic shema?
My JVC S11 amp, doesn't work actually. I know why, relay doesn't work, but i need the electronic shema to check it.

Thank you

Loic

 

[xxxxxxxxxxxxxx]

Uhhh the link is in the very quote you poseted. Signup for free and download the schematic for free...