ESP Project 104 muting problem

[kjb]

Hello!
I'm trying to finish a Linkwitz Orion ASP upgrade and adding a mute circuit. There is a problem when cutting the power it wont mute.

The circuit Project 104 - Preamp/ crossover muting circuit



The problem is that there is a voltage on pin 1 to the AC trigger part despite the fact that the ac is cut. It has to go low before the circuit mutes . (should happen 50ms after ac is cut)
Its two diodes between GND and positive rail. In the middle there is pin 1. It seems like i get half voltage (like a voltage divider) between GND and +5.5 V (I'll use a 5.5V zener) The level is always high. I can mesure ~2.8 V slowly decreasing when the external filter caps drains.

I use full rectifier bridges. two instead of only one described in the article.
Anybody knows whats I'm doing wrong? This is driving me mad
Thanks for all suggestions!

[Mooly]

Just some thoughts...

The 100k to pin 1 has to be "ground referenced" which would normally be via the transformer. In other words the left hand end of R1 should read essentially zero ohms to ground. Check it ? Have you got it connected to the AC on the tranny and not the rectified rails ?

Without seeing how you have wired it up it's hard to say.

Check the remainder of the circuit...

If you lift D3 the circuit should mute/unmute as you short out C1.

[kjb]

That's was the problem I had hooked it up like this.

The ac was from one of the secondaries, and the positive rail is taken from the same rectified secondary, same with the GND.

I removed one bridge and connected it like it should and now it works perfectly.
But now the regulation is worse i guess. But i will use superregulators so thats probably not a problem
Thanks!

[Mooly]

Thanks for the update...

[AndrewT]

This may solve the problem of not recognising the "loss of AC"

Tap directly to one secondary. Use a diode to rectify that AC.
Connect the half wave rectified signal to the 100k.