5F6A ?

[chuckb]

Hey guys ,I'm building a 5F6A and the PT transformer doesn't have a 5v tap for the rectifier. I've got a 5vCT/6A transformer and was wondering if I can use this for the rectifier? It has 2 yellow wires and a yellow/green CT on one side and two black wires on the other. I'm assuming that the two yellow wires go to pins # 2 & 8 of the rectifier and the yellow/green CT wire goes to ground. Also the two black wires ,do one go to the power supply and the other to ground? Is this the way I'm to hook up this transformer? Thanks in advance.

Chuck.

[Chuck H]

You won't use the CTR on the secondary for this app. Just cut it and shrink tube the end. The two black wires go to your AC mains power.

Chuck

[chuckb]

Thanks Chuck, So do I just wind the two black wires together and attach them to my mains or one to my mains and the other to my stby switch?

[JoeM]

Are you absolutely set on using a tube rectifier? You could use a Weber Copper cap and do without the hassle of installing the 5V transformer.

[chuckb]

Hey Joem,
I haven't decided to use the transformer yet and I'm thinking about using a ss rectifier. I was thinking about making my own using 4n007 diodes.I believe I need a full wave rectifier? Any suggestion on how to accomplish this would be greatly appreciated.

Charles.

[JoeM]

Hey Joem,
I haven't decided to use the transformer yet and I'm thinking about using a ss rectifier. I was thinking about making my own using 4n007 diodes.I believe I need a full wave rectifier? Any suggestion on how to accomplish this would be greatly appreciated.

Charles.

What PT are you using? You can do it with the 4007 diodes, but whether you need a full wave bridge, etc, will depend on the PT. Do you have the specs on the PT?

[chuckb]

Well I believe I need a full wave diode retifier because I have no 5v winding but I do have a CT. The transformers are from a Gibson GA-45RVT.

[JHow]

I thought GA-45RVT had centertapped secondary and two diodes for rectification for B+. Do you have only two red wires coming for the secondary or also red/yellow? (and a blue for the 50V tap?)

[chuckb]

Yes, I have all the wires you mentioned,2 reds ,red/yellow on the secondary and a blue 50v bias supply.

[JHow]

Then you should be good to go with "full wave two-phase" rectifier, but not a "bridge". One diode (or several in series) off each red to the top of your first filter, Red/yellow CT to ground. Probably ignore the blue (heat shrink the end), unless you are setting up a bias supply.

[chuckb]

How will I know how many diodes to use in series for each red wire?

[JHow]

Depends on how high is your B+. Putting diodes in series will increase the voltage rating. Valve wizard gives a rule of thumb to shoot for a (PIV) rating of 2.8 times RMS voltage:

The Valve Wizard

If you are in neighborhood of 3oo rms, you should be fine with single 1n4007 on each leg.

VW also suggests using caps in parallel with the diodes to share voltage.

[JoeM]

Depends on how high is your B+. Putting diodes in series will increase the voltage rating. Valve wizard gives a rule of thumb to shoot for a (PIV) rating of 2.8 times RMS voltage:

The Valve Wizard

If you are in neighborhood of 3oo rms, you should be fine with single 1n4007 on each leg.

VW also suggests using caps in parallel with the diodes to share voltage.

I would use at least 2 1N4007 in series in each leg. Even 3 gives a higher margin and the diodes are cheap.

[JHow]

Good point. They are cheap.

[Bruce / Mission Amps]

"Hey guys ,I'm building a 5F6A and the PT transformer doesn't have a 5v tap for the rectifier. I've got a 5vCT/6A transformer and was wondering if I can use this for the rectifier? It has 2 yellow wires and a yellow/green CT on one side and two black wires on the other. I'm assuming that the two yellow wires go to pins # 2 & 8 of the rectifier and the yellow/green CT wire goes to ground. Also the two black wires ,do one go to the power supply and the other to ground? Is this the way I'm to hook up this transformer? Thanks in advance."

NO NO NO... never ground that yellow/green wire!!
Black wires are in parallel with the other primary wires of your PT... make sure the filament PT is protected with the mains fuse.

If your 5v tranny has three secondary wires of which one is a yellow/green center tap, that Y/G wire from the tranny is the wire you use to feed the high voltage B+ to the standby switch and over to the filter caps.
In that configuration, nothing comes from the rectifier tube socket to feed B+ anywhere.