12v AC to 12v DC

[andrew]

I have a both a 12v and a 6v filament supply and I would like to convert the 12v to DC. I found this schematic but I have a questions. Here is the schematic: http://lh-electric.net/vtps02.html
If I make the bridge rectifier what diodes should I use? Thanks for any help.

[selloutrr]

should be fine with a 1N4007 or search digikey or mouser for a dedicated rectifier.

[andrew]

Thanks for the help!

[RJ Guitars]

I was thinking of using this to power my heater filaments with DC - it is a pretty simple DIY layout... let us know if how things work out with whatever you build. thanks rj

[andrew]

Thanks RJ, I will try your circuit and I have the parts . I have a question about grounding the center taps though. My first post had a schematic for a 12.3v ac-dc conversion and a schematic for a 6.3v ac-dc conversion. The schematic for the 12v doesn't have a grounded center tap but the schematic for the 6.3v does. I don't understand.( I have my 6.3v ac heaters on the power tubes and its center tap is grounded on a PT lug.) After the ac-dc conversion what should I do with the 12v center tap?

[RJ Guitars]

Andrew,

For the board that I designed you won't use the center tap... it will in fact cause you grief. You can tie it off or cut it short and insulate it if you are certain you'll never use it. I suggest tying it off until you have your circuit working the way you want it to.

Also, take a look at this thread, it takes this topic a little further. https://tubeamparchive.com/viewtopic.php?t=17832

I look forward to your report on how this turns out.

rj

[Structo]

I think you may want to up the filtering if you use it for DC Filaments.

I would use a couple 1000uF 25v and at least one film cap of say, .01uF.

[andrew]

Thanks Tom.

[RJ Guitars]

Yes Tom is on top of that... that little DC supply was designed as a supply for operating relays and it isn't filtered enough for a heater supply. rj

[paulster]

I think you may want to up the filtering if you use it for DC Filaments.

I would use a couple 1000uF 25v and at least one film cap of say, .01uF.

The film cap won't make any appreciable difference since the overwhelming amount of noise remaining will be from the charge/discharge cycle.

For each amp of current drawn you want 10,000uF to get your ripple down to 10% as a broad rule of thumb. I'd want a whole lot less than 10% ripple on my heaters as it's a saw-tooth wave which sounds way, way nastier than the nice clean sine wave of AC, so calculate the current drawn and work from that.

[gingertube]

A little off topic.
I needed a 6.3V DC supply for a preamp tube on a recent project.

The existing heater winding on the powerc tranny was fully loaded.

What it did have was an unused 5V AC winding intended for a rectfier tube.

A bridge of 1N5822 schottky diodes (for low forward voltage drop) and a 10,000uF capacitor gave me 5.97V DC under a 300mA load. Close enough for even the most demanding applications.

One to keep in mind.

Cheers,
Ian