Is the power LED on the KA-7100 part of the protection circuit?

Robisme

Sansui Enthusiast
I am working on a KA-7100 that did not come out of protection. I tested the outputs, drivers, DC offset at the relay, and bias. All OK.

I decided to replace the power LED before I went any further, and when I connected the new one (I had it powered up) it came out of protection. Disconnected the LED and back into protect it went. Reconnected LED and out of protect again.

Installed the LED and it works fine. I don't have the schematic.

Rob
 
Yes, the pilot LED is part of the AC loss detect circuitry...if the LED goes open, the protect circuit behaves as if AC power has been lost and opens the speaker relay.

I had forgotten that little tidbit of info...has been a while since I saw a 7100 with a duff LED.
 
Yes, the pilot LED is part of the AC loss detect circuitry...if the LED goes open, the protect circuit behaves as if AC power has been lost and opens the speaker relay.

Thanks.

I would think not many amps are configured that way.

Rob
 
Yes, the pilot LED is part of the AC loss detect circuitry...if the LED goes open, the protect circuit behaves as if AC power has been lost and opens the speaker relay.

I had forgotten that little tidbit of info...has been a while since I saw a 7100 with a duff LED.
Hi, I’m new here.
I need a new LED for my KA-7100. I pinched the wire while putting it back together after a recap and killed it.
I put in a random LED I found in my garage to see if it would work and it does except now the protection relay does it’s thing after about 4 minutes of playing a CD. I tried to set the bias before connecting speakers but the relay would only stay on for about 10 seconds.
Can someone please advise me on the correct LED? I bought this amp new in 1978 and I want to get it working again for sentimental reasons. Thank you!
 
What test points were you using?
The speaker terminals. It reads 2.3V then rises to about 2.6 when the relay cuts it off in about 30 seconds. I connected speakers and a CD player and it works for 3 or 4 minutes before the relay shuts it off.
 
Thanks.

I would think not many amps are configured that way.

Rob
What did the original LED look like. Did it have a 2mm pin on top? Like this one?
https://www.newark.com/webapp/wcs/s...estType=Base&partNumber=14N9442&storeId=10194

Or just an ordinary dome top?
What did the original LED look like. Did it have a 2mm pin on top? Like this one?
https://www.newark.com/webapp/wcs/s...estType=Base&partNumber=14N9442&storeId=10194

Or just an ordinary dome top?
I don’t see the picture you linked. I’ll try and post what I used. It came out of a bug zapper that looks like a little tennis racket.
 

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I don’t see the picture you linked. I’ll try and post what I used. It came out of a bug zapper that looks like a little tennis racket.
Sorry, I see it now. I thought you wanted to see the replacement. Here is the original...
 

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Hi, I’m new here.
I need a new LED for my KA-7100. I pinched the wire while putting it back together after a recap and killed it.
I put in a random LED I found in my garage to see if it would work and it does except now the protection relay does it’s thing after about 4 minutes of playing a CD. I tried to set the bias before connecting speakers but the relay would only stay on for about 10 seconds.
Can someone please advise me on the correct LED? I bought this amp new in 1978 and I want to get it working again for sentimental reasons. Thank you!
You are actually trying to adjust the center voltage(dc offset) not the bias. Can't adjust bias at the speaker connections.
You are actually trying to adjust the center voltage(dc offset) not the bias. Can't adjust bias at the speaker connections.
 
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