12 to 6V/15A voltage regulator

Thread Starter

Fer870

Joined Mar 10, 2020
4
Hello guys, new member here, i'm looking for a voltage regulator circuit, which i can use to mount an old 6V radio on a 12V car.

The requirements are:
Output voltage: 6.3V
Average current (from the radio's manual/schematic): 5.5A
Maximum current (based on the fuse used by the radio): 15A

I've researched a bit, but the circuits i found either couldn't keep with 15A loads, or when brought up were mentioned as "bad designs"
 

Thread Starter

Fer870

Joined Mar 10, 2020
4
I've been looking into something similar and there is a sample circuit here: https://www.eleccircuit.com/high-power-supply-regulater-0-30v-20a-by-lm338/
Thanks, i'll take a look

hi 870,
Welcome to AAC,
Use a 12vdc to 6vdc 5amp buck converter, more efficient than linear types.
A while ago i looked into buck converters, but couldn't find one that handled the current. Now i can find a few rated for (depending on the model) 6-8A continuous, and 10-12A max (with a cooler). My question is, since the radio would be most of the time at 5.5A with 15A being the maximum peak, would i be ok with using a converter like the ones i mentioned?

First make sure the 6v radio isn't positive ground, some are and some aren't...
I'm looking into that. I believe it is indeed positive ground, but some people say that since it uses a vibrator in the power supply, the input polarity doesn't matter, while others say i should just replace the vibrator to change the polarity
 

crutschow

Joined Mar 14, 2008
24,749
My question is, since the radio would be most of the time at 5.5A with 15A being the maximum peak, would i be ok with using a converter like the ones i mentioned?
I think the 6-8A converter would be sufficient.
It's unlikely to get above that current if the average is 5.5A.
 
I once had a radio pulled out form a 1953 VW.
It used a mechanical vibrator to step up the 6 volt to the high voltage anode supply with a transformer.
The tube's heaters were fed directly from the 6 volts.

So nothing should be damaged if you invert the polarity.
 

Thread Starter

Fer870

Joined Mar 10, 2020
4
What radio is that? 5.5 A is a lot of current.
33W is probably typical for a tube radio.
Must be a Valve Radio then, the vibrator is for the HV for the Anodes...
You can replace it with a mini buck booster..
Yes, it's a valve radio- 1949 Automatic M-90

Dodgydave, i don't think it's possible to replace it. the power supply goes vibrator-transformer-rectifier. Did you mean replacing them all with a 6.3V DC to B+ DC booster? (i still need 6.3V for the valve heaters)
I think the 6-8A converter would be sufficient.
It's unlikely to get above that current if the average is 5.5A.
Ok, i think the buck converters are the way to go then

I'm looking into that. I believe it is indeed positive ground, but some people say that since it uses a vibrator in the power supply, the input polarity doesn't matter, while others say i should just replace the vibrator to change the polarity
I remembered now, this radio was on my grandfather's truck, which has a 12V negative ground system (the battery was tapped to supply 6V). If it worked back then, it means the radio doesn't care about polarity. i just need the regulator because i can't tap modern sealed batteries...
(As i was writing this message, schmitt trigger posted his, confirming my suspicions)
 

Dodgydave

Joined Jun 22, 2012
9,090
Yes, it's a valve radio- 1949 Automatic M-90

Dodgydave, i don't think it's possible to replace it. the power supply goes vibrator-transformer-rectifier. Did you mean replacing them all with a 6.3V DC to B+ DC booster? (i still need 6.3V for the valve heaters)

Ok, i think the buck converters are the way to go then


I remembered now, this radio was on my grandfather's truck, which has a 12V negative ground system (the battery was tapped to supply 6V). If it worked back then, it means the radio doesn't care about polarity. i just need the regulator because i can't tap modern sealed batteries...
(As i was writing this message, schmitt trigger posted his, confirming my suspicions)
I remember these had two twin triode valves, with 6.3V heaters, the ht is around 200V, a simple royer oscillator will do for the HT supply instead of that buzzing pesky vibrator..
 

Thread Starter

Fer870

Joined Mar 10, 2020
4
I remember these had two twin triode valves, with 6.3V heaters, the ht is around 200V, a simple royer oscillator will do for the HT supply instead of that buzzing pesky vibrator..
Well, looking at the voltage chart below, the rectifier puts out 265V, so i could replace the vibrator( 6V DC to 6V pulsated DC), transformer(6V Pulsated to 300V AC), and rectifier(300V AC to 265V DC), with a single 6-265V DC/DC device. i will look into the royer oscillator you mentioned.

If it wasn't for the 6.3V tube heaters, i could simply use a 12-265V step up and connect the radio directly to the car. I know i could replace the tube for their 12V equivalents, but a complete tube swap costs ~3 times more than a converter...
Anotação 2020-03-11 170738.jpg
 
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