Soft start timing question again...

[rtate]

I have just installed  the soft start circuit in one of my mono blocks and it works perfectly.
I currently have 2 uf capacatance for C4,5.
I do hear 2 distinct clicks of the relays when starting up and R1 is 2x 100 ohm 20 watt resistors.

I would like to make the delay longer possibly3-4 seconds if possible.
My question is how far can I push out the time delay safely? and any suggestions for capacitor values?

Thanks

[peranders]

You can have the delay longer but I don't know where the exact limit is. Notice that the circuit is rather complicated despite the simplicity. I have used LTSpice in order to tune the circuit.

May I ask why you want the delay to be longer?

[rtate]

I have 7 mono blocks to turn on and I would like to do it with one switch, so I thought that I mifgt need a little more time to avoid that large in-rush of current....

[peranders]

How big are the transformers? What fuse rating do you have? Do you run all amps on the same fuse? What type of relay do you use, Schrack 8, 16 A?

[rtate]

The transformers are 1000va and have 6 1/4 amp fuses on each rail  with 120vac fed from a  single dedicated 20 amp breaker  and 10 gauge wire.
The relays are 16A type.

[peranders]

You mean you have 7000 VA and a 16 A relay. This is too weak. This is also to much for your fuse. 120 Volt and 20 is only 2400 VA. Each amp should have it's own softstart. The pcb is made for 8 A, possible a little bit more.

[rtate]

sorry for the misunderstanding..

each amp will have its own soft start.

I have a relay in the feed circuit that drops out if there is a power fail so that they don't all start up at once if power is restored and i'm not there.
Presently if there is a power fail I turn all of the amps off and then reset the relay and start the amps up one at a time.
I was hoping that installing the soft starts in each amp would alow me to  eliminate the step of turning all of the amps off and just reset the control relay.

[peranders]

To answer your question: The delay time ca be increased but I can't guarantee the function for more than I have tested

[rtate]

So if i increase C4 and C5 do I need to adjust R11 as well?.
What will a higher or lower resistance have on the timing of the circuit?

[peranders]

C4, C5 can be increased but be careful about R11. If you are using transistors with Hfe 500 or more you can increase R11, possibly to 1 MOhms but star with increasign C4, C5. If you right now don't have any fuse blowing problems, you won't have to do anything.