Chattering Relay in Krell KSA-250 - Page 2

johnnyx · 15th May 2004, 10:05 PM

This kind of circuit senses the ac voltage from the power transformer independantly of the main reservoir caps. It will probably use a large series resistor and cap to give the 2 sec delay. there will probably be a diode in reverse to discharge this cap quickly when switched off. I don't know the actual circuit, but they all provide the same function. The time constant is chosen so that it will give a steady output voltage, and hence relay switched on, during the 10mS pulses from the transformer.
time = 1/f = 1/100Hz = 10mS
If the time constant is say 12ms, then the output will be steady. When the power is switched off, the relay switches off after 12mS.
If the fault reduces the time constant to say 5mS, then the relay will see pulses instead of a steady voltage, causing relay chatter.
There are many ways to achieve this. there may be two seperate timing devices, one for turn on delay, the other for turn off delay.

Try to identify and change the components in this circuit.
Krell might use a tricky-dicky circuit, just because it's Krell.

Hope this helps.

K-amps · 15th May 2004, 10:20 PM

Thanks Echo and Johnny,

Looks like I will need to spend more time than I thought initially.... I just hope there are no custom IC's ... I suck with IC's

ericwwk · 1st February 2012, 01:01 PM

Quote:

Originally Posted by K-amps

Thanks Echo and Johnny,

Looks like I will need to spend more time than I thought initially.... I just hope there are no custom IC's ... I suck with IC's

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15th May 2004, 10:05 PM	#11
johnnyx diyAudio Member Join Date: Jan 2004 Location: manchester	This kind of circuit senses the ac voltage from the power transformer independantly of the main reservoir caps. It will probably use a large series resistor and cap to give the 2 sec delay. there will probably be a diode in reverse to discharge this cap quickly when switched off. I don't know the actual circuit, but they all provide the same function. The time constant is chosen so that it will give a steady output voltage, and hence relay switched on, during the 10mS pulses from the transformer. time = 1/f = 1/100Hz = 10mS If the time constant is say 12ms, then the output will be steady. When the power is switched off, the relay switches off after 12mS. If the fault reduces the time constant to say 5mS, then the relay will see pulses instead of a steady voltage, causing relay chatter. There are many ways to achieve this. there may be two seperate timing devices, one for turn on delay, the other for turn off delay. Try to identify and change the components in this circuit. Krell might use a tricky-dicky circuit, just because it's Krell. Hope this helps.

15th May 2004, 10:20 PM	#12
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	Thanks Echo and Johnny, Looks like I will need to spend more time than I thought initially.... I just hope there are no custom IC's ... I suck with IC's

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