Possibly silly question about powering relays...

[Paul-in-KC]

Okay - so, I have decided to build a 50W (non-HRM) Low-Plate ODS.

From what I have looked at thus far, I presume the Layout by Tony Albany and schematic from MD Roberts are pretty good sources to work from (this is really a separate question).

Here is my primary (possibly silly) question. Why do you/we need to use a separate transformer (F-313X) to power the 12 VDC relay - when we already have the ~6.3 V from the power transformer? Would activating the relay draw too much current? Looks like there are 4 amps available on the Classic-Tone PT that I bought. Not sure what the draw is for all of the heater elements though. But 4 amps seems like a lot of power.

I'm sure there is a reason - just not sure what it is (probably total draw?).

And if I may throw in a related question while we are here. Can anyone share a specific part # for an appropriate relay?

Many thanks as always to those who share their knowledge here and are always so generous. You guys are awesome!

-Paul

[mojotom]

I think the separate relay transformer was choosen for noise consideration.

A dedicated power supply won't introduce hum as it could if the heater supply is used for both heaters and relay power.

That being said the twin power transformer didn't have any additional taps available like the Bassman do (additional 5v rectifier heater) so maybe he used a separate transformer in that case.

I've used 5V taps to power 5V relay on my 70's build (Bassman PT) and I've used an extra 5v tap on others builds as it feels easier to me to wire (in that case 12v relays using a doubler without any rectifier).
Didn't have any noise issue.

You should be able to find a 50W PT with a 5V rectifier tap and use it for your relay supply.

[amplifiednation]

Yeah - use a bassman PT with the rectifier taps. It's so much easier and cleaner. Or if you don't have one, Triad makes a killer little transformer F-313X with dual primaries.

[Paul-in-KC]

Yeah - use a bassman PT with the rectifier taps. It's so much easier and cleaner. Or if you don't have one, Triad makes a killer little transformer F-313X with dual primaries.

Thanks Taylor.

Yeah, had I realized -- the Bassman PT would have been my choice, but I already purchased the PT. So, I went with the Triad F-313X.

If I build another, I'll go the Bassman PT route.

-P.