Need Help About Speaker Relay!

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Thank you for relying.
What I mean was "can the relay kick on if the OUTPUT TRANSISTORS WERE TAKEN OUT OF THE CIRCUIT BOARD?"

Without the OUTPUT ...C: 33 Volts, Bass: 32 Volts, E: 0 Volts. When I put the OUTPUT back in the circuit board
then the Bass turns to be zero Volts ????
 
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If the relay control circuit is designed properly it will not turn them on if there is any appreciable DC on the output of the amplifier.

An amplifier without any output transistors might show one of the rail voltages on the output, this would stop the relays from closing.

On the other hand, if the output transistors had blown and the rail fuses blew as a result, then there might be no DC on the output and the relays will close. That is if the relays and control circuitry are not powered after the amplifiers rail fuses.

What is it that's gone wrong?
 
...ansewering to MAXPOU. I removed the output transistors for safety. However, the Amp is working execpt the relay does not kick on because of the IC C1237.
I got the audio output before the relay. So far, I have replace the UPC1237HA.

Thank you so much to all the friends in this forum !
 
AX tech editor
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...ansewering to MAXPOU. I removed the output transistors for safety. However, the Amp is working execpt the relay does not kick on because of the IC C1237.
I got the audio output before the relay. So far, I have replace the UPC1237HA.

Thank you so much to all the friends in this forum !

The UPC1237 will keep the relay open if there is a little DC on the output. Can you measure the output DC with no signal?

jd
 
AX tech editor
Joined 2002
Paid Member
The output DC with out the signal is 0.027 Volts.

That should not make the 1237 open the relay, you need several 100mV for that (depending on exactly the circuit around the 1237).
Could it be that the supply voltage for the relay and/or the 1237 is also removed when you removed the output stage? Do you have a circuit diagram?

jd
 
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