powering a relay

[lowell]

Hey great thread. I'm considering using my 5v tube rectifier tap for a 5v relay supply. I am using a 5Y3 tube rectifier. There is no center tap on this winding so I'm thinking I would need to use a bridge. Also would I ground the bridge to earth or leave it floating and tie the relay supply cap to that point?

5v_relaysupply_earth.pdf

5v_relaysupply_no_earth.pdf

[J M Fahey]

Hey great thread. I'm considering using my 5v tube rectifier tap for a 5v relay supply. I am using a 5Y3 tube rectifier. There is no center tap on this winding so I'm thinking I would need to use a bridge. Also would I ground the bridge to earth or leave it floating and tie the relay supply cap to that point?

[ATTACH]13260[/ATTACH]

[ATTACH]13261[/ATTACH]

Hi Lowell. The above suggestions refer to an *unused* , *free*, connected *nowhere else* 5V winding. (not "tap" because it's no part of any other winding).
IF you are using your 5Y3 as rectifier, that 5VAC winding is already sitting at +400V DC (or whatever your +B is) from ground.
Forget using it for anything else.That's why there is a *separate* (and well isolated) winding, also why they chose to use 5V instead of 6.3V: so you do not even try to use fo any other tube.

[lowell]

oh yeah... duh. good call... thanks! Guess I'm stuck with using the filament winding. At 4.5vdc rectified that should be sufficient for a 5vdc relay. At least the ones I'm using which have a minimum voltage of 3.75vdc.

[txstrat]

Here's what I did with my latest build. see pic. But I'm using a diode rectifier and don't need the 5vac winding anyway. For those who are inerested:

The first cap of the voltage doubler needs to be roughly double the value of the second. I'm using way to big caps here for feeding one relay only. But it's dead quiet. The voltage I'm getting is even enough to power a 12v relay.
I'm using a red LED in series with the ground wire (in a footswitch) which lights up when I switch the relay on.
The second diode in series is not necessary and I'm using it to separate the first from the second (parallel) cap. Haven't tried if it makes any difference if I leave out 2nd diode and 2nd cap.

[lowell]

nice work. I really think it's too many components. Why not just use the 6.3 filament winding and 5vdc relays instead? One full wave rectifier and 1 cap... bam.

[txstrat]

I've tried that but I got a bad buzz from the relay coil. I'm switching two different master volume pots (after the tone stack) in a sort of 5F6A circuit. Also I needed the additional voltage for the LED.

[Alex R]

Mesa often supply their relays this way, definitely. This I know because two of the most nightmarish repairs I have ever had to do in Mesas have featured that rare beast a HT-to-filament short which went on to fry half of the switching circuit (before, I guess, the rectifier went open circuit). How might one protect against that?

[J M Fahey]

Yes, you can do that.
Not the best, but should work most of the time.
Of course, using *mechanical* switches; the .7 to 1V lost in a switching transistor will be too much in this case.

[lowell]

Here's a quick draw up for 5v relays using only a full wave and 1 cap from the filament winding.

[J M Fahey]

Good.
That's the way to do it.