Hi, I hope somebody can help me solve this problem. I have made the kit for use with a Quad 405 amp. When connected one channel detects a fault and the red led stays on, but the Amp is OK. If I connect this amp to the other channel it is OK. Both mono amps act in the same way. I have checked and double checked wiring and component layout. Any ideas?
Sorry, we are confused:
Is one channel of the K4700 working correctly and the other one isn’t?
Yes.
On one channel of the K4700, the red led lights and the relays will not close when the amp is connected. The other channel is fine.
Most likely an assembly problem.
Both channels are identical.
This allows you to compare signals.
Ground both inputs of the K4700 and compare signals:
Connection R21/R3/R1 and R22/R4/R2
Check level on inverting and non-inverting pins of A1…A4 of op-amp (see LM324 datasheet for pinout)
Please excuse my ignorance, but when you say ground both inputs, do you mean ground both PA connections instead of connecting them to the amp speaker outputs?
Yes, do not connect them to the amp inputs and ground them instead.
Hi, Thank you for your help. I have found the problem. Excess solder. I am most grateful for your quick and thorough response. Best regards Barry
Happy to read it is working fine now.