Relay supply from a 6.3V tap ?

[deiseldave]

If the amp rating is high enough, can you derive your relay supply from the same 6.3V tap that the heaters are using ?
If so, can you direct me to a scheme or layout of a working design to study ?
Thanks in advance for the help.
Deiseldave

[marshmellow]

Sure, no problem. I would use a standard voltage regulator circuit (bridge rectifier -> fat electrolytic cap -> regulator -> 100n cap) using a 7805. Or 7806 or whatever DC voltage you're aiming for. But about 6V will be the upper limit. Or squeeze out another volt using a low drop regulator.

[deiseldave]

Thanks for the response.
I had planned on keeping my heaters AC, and Thought I would just parallel off the 6.3 tap with the DC relay ckt ? Am I correct with that ?
Also, can you recommend any drawings ?
Thanks,
Dave

[marshmellow]

Well, Google would have answered that since it's probably one of the most common circuits ever... Anyway, just drew it up for ya here.

[deiseldave]

Well, Google would have answered that since it's probably one of the most common circuits ever... Anyway, just drew it up for ya here.

You know, I thought it would be common and easy to find, too. But, last night I spent hours Googling, and searching AmpGarage, AX84, 18Watt, PPWatt, and just couldn't find anything clear cut on it. Maybe I wasn't combining the magic search string. I dunno. So, I figured to just ask.
Thanks Marshmellow, I appreciate you taking the time to help me.

[briane]

I've used one sold by weber, some sort of channel switcher....

It works fine, though the directions were non-existent, so it took a while to choose the right hookup. No humm, though still need to check that the led in my footswitch isnt screwing with the voltage as well (he does not discuss appropriate footswitches for the circuit), though I did have to swap out the heater centertap and instead use the 2x100 ohm resistor ground ref.

That amp did not have a 5v tap on the PT. If youve got the 5V its a lot less expensive to go that route.

[Ears]

Hi Dave,

Reading between the lines of your last two threads...are you planning to run DC heaters from the 5V tap and the relays from the 6.3 taps?

[deiseldave]

Hi Dave,

Reading between the lines of your last two threads...are you planning to run DC heaters from the 5V tap and the relays from the 6.3 taps?

Pretty much. I'm planning on a 6V6 Dlite-esque.
320VAC @180ma -> B+ PS
50VAC tap -> BIAS PS
6.3VAC @4A tap -> 6V6's heaters -> relay PS -> SSR's
5VAC @3.5 tap -> bridge rect + 1000uf @10V -> 12AX7's

[drz400]

With the foward voltage drop of the diodes that 5 volt is going to be on the ragged edge and with 1,000 uf it might not be worth trying DC at all, 10,000uf would be minimum.

[marshmellow]

You know, I thought it would be common and easy to find, too. But, last night I spent hours Googling, and searching AmpGarage, AX84, 18Watt, PPWatt, and just couldn't find anything clear cut on it. Maybe I wasn't combining the magic search string. I dunno. So, I figured to just ask.
Thanks Marshmellow, I appreciate you taking the time to help me.

You're welcome, never mind. Just wanted to point out that possibilty . Feel free to ask further questions.

[drz400]

Well, Google would have answered that since it's probably one of the most common circuits ever... Anyway, just drew it up for ya here.

this would provide about 6.9 to 7.7 volts at the regulator input of the
regulator. A 7805 needs a minimum of 7.5 volts at its input. This could be
modified to an LDO regulator such as an LM2940 which will provide more margin
(headroom).

[jaysg]

Use Schottky rectifiers for less voltage loss...like the 1N5821

[deiseldave]

Wow ! Thanks for all the great info.
This amp will be kind of a "mutt" of spare parts, combining some of the interesting designs I've looked at across the various forums.
What I want to build borrows alot from the Dlite, except I want to use:
* Mark Huss' Mosfet switching design,
* 5V tap rectified for preamp tubes,
* 6.3v tap feeding 6V6's, and relay supply.
* B+ PS changes (still working them all out)
* Dana's VVR2
The parts that I have bought so far are:
(1) 1X12 Combo Cab, chassis, & transformers (JudyBox Amps garage sale).
PT is: 320-0-320 or 265-0-265 @ 150, 50V bias, 6.3V @ 4A, & 5V @ 3.5A.
OPT: 40W 4K/8K primary
(1) VVR2 purchased from Dana
Garolite, eyelets, and some other parts from Turretboards.com.
I certainly appreciate all the help so far, and promise to fully disclose any lucky magic that may happen.
Who knows ? Serendipity sometimes knows not the lap into which she falls.

[marshmellow]

Well, Google would have answered that since it's probably one of the most common circuits ever... Anyway, just drew it up for ya here.

this would provide about 6.9 to 7.7 volts at the regulator input of the
regulator. A 7805 needs a minimum of 7.5 volts at its input. This could be
modified to an LDO regulator such as an LM2940 which will provide more margin
(headroom).

Well actually it depends on how much current you draw and the temperature. Looking at the datasheet (at least the one I have here) you can see that you're well below 2 volts dropout under normal conditions. But you're right, overhead is on the short side, that's why I already mentioned the low dropout regulator. And the Schottkys jaysg mentioned are also a good idea.