B+ time delay relay

[nigelwright7557]

I use a PIC micro in my amp.
It currently holds off the output to teh speakers for 3 seconds.
It also monitors b+ and B- for a DC condition and switches off output to speaker if it spots a fault condition.

No reason why I couldnt add another relay to hold off B+ for a few seconds.

 

[jeepy]

OK, after getting my PSU (more-or-less) designed, I want to add a time-delay relay so that a single switch can be used to turn on the 6.3VAC heater transformer before the B+ transformer gets switched-on.

An article in Sound Practices shows how to do the job with 2 switches only!
On top of that you can heat your tubes for the time depending on your mood!

 

[jeepy]

cbutterworth,

This works well. Also why not use the 'inactive position' of the relay to connect the power line to ground thru a 5-10k resistor so when you swith off the main you discharge quickly the psu capacitors who keep high voltage
longer than the heaters get cool.

 

[tubekit]

What about just using one of these, or something like it?

115C20T - Relay, time delay. 20-sec 115V SPST-NC-3A 9-pin - Relay_ time delay_ 20-sec 115V SPST-NC-3A 9-pin - 115C20T/

$20. Put it in the plate primary and use a separate filament tranny.

 

[ratbagp]

Another old solution that uses a separate filament transformer and two DPDT switches that are rated at normal 120 or 240 line voltages. I get mine from Radio Shack.

Dual DPDT Switch

It's simple and works well except if there is an outage followed quickly by the restoration of power. It's actually not that much of a disadvantage since the tubes are still warm.

ray