K4700 not functioning well?

Kits Audio Hi Fi Projects
1

Hello,

after a three years of flawless operation my K4700 started to switch off the speakers. It happens shortly after i switch on my stereo set (Quad 34 and Quad 405). Without the K4700 the set works fine. The sound is not cut off directly, but with a crackling noise.

The functional check of the k4700 is OK: yellow light dims, connecting PA (L & R) to V- results in a click of the relays and the red led lights up.

What seems to be remarkable is the way the unit is activated. After about 6 secs the yellow led dims. But the clicking sound in the relays is very low: it is not a clear or strong click.

Can there be something wrong with the circuit? How to check if all is OK?

Thanks in advance.
Eric

2

Because this is an analog circuit, the problem could be a lot of things

T1,T2,T4,ZD1 the IC LM324,…
Start to check the transformer.

You must understand that it’s not possible for us to say what the problem is w/o checking out the kit.