5V supply for the relays, is 6.3V ok?

[Tdale]

I'm rewiring an amp that has two separate imputs, so that it can switch between the two preamps, using a relay.

I made relay switching for my Dumble, using the 5V tap as a power source. It worked fine, using a bridge, cap and voltage regulator.

I want to do the same now, but the PT doesn't have a 5V secondary. It has however two 6.3V secondaries, one 3A and one 4A.

The way the amp is wired now, I use both secondaries for the heaters, one for the four EL84's, and the other for three 12AX7 and one EF86. None of the 6.3V secondaries have a center tap, so I'm using 100 ohm resistors to ground.

So to my question. Is it ok to wire all the heaters to the 4A secondary, and use the other for my relay power supply? The bridge and the voltage regulator can handle much more than 5V, so there shouldn't be a problem, right?

But I can't use one of the secondaries for both heaters and relay power supply at the same time, right?

Tommy

[VacuumVoodoo]

What type of relay are you using? Look at the specs for max coil operating voltage, many 5V relays are ok up to 7V or 8V.
How much curent do they need?

If you're running EL84 heaters off 4A winding you have ca 1A reserve. Run yor EL84 heaters on AC and you can get ca 400mA dc available for relays.

You can still rectify 6.3V resistor censtered winding with a bridge and get ground referenced +3.15V & -3.15V dc to operate the relays. See attachement, relays are footswitch activated. The switches connect 2.7k resistor to either +3.15V or -3.15V.

The trick to avoid switching clicks is to run heater winding wires t the bridge first and then run 6.3Vac to El84 heaters.

[Tdale]

The relays will be fine with that voltage.

My main concern was if I had to separate the heater circuit from the relay power supply circuit.

I'm attaching a pic of the circuit. Forget about the right side, the switches will be a little different, but the bridge, cap and regulator wil be wired that way. The bridge will be grounded, but the grounding symbol is not drawn...

I thought I read something about the Weber relay boards that connect to the 6.3V, that they only worked if there is no center tap. But I guess that's different.

[VacuumVoodoo]

The relays will be fine with that voltage.

My main concern was if I had to separate the heater circuit from the relay power supply circuit.

You don't need to separate the circuits. Just make sure you have snubbers over relay coils and switches.

[Tdale]

thanks!

[Tdale]

Just to be sure..

If I were to ground the 6.3V secondary on one side in stead of using the 100 ohms resistors, would things still work with the full wave rectifier bridge setup?

Tommy

[VacuumVoodoo]

You would have to leave rectified dc floating which is not a good thing.
I'd recommend to balance the 6.3V ac with 100 Ohm resistors AND connect bridge (-) to ground to minimize hum and spikes from bridge.

[drz400]

I find a separate supply for the switching is usually more quiet
Certainly cheap enough to buy that tranny, no reason to be lazy