CCS Filament Regualtors for split filaments
I’m using a ECC99 from JJ Electronics. This tube has a split filament – two 6.3V heaters wired in 12.6V series (using 400mA). Generally, I’ll put the two in parallel and run the heaters using 800mA 6.3V (my transformer doesn’t have a 12.3V tap).
I want to change to a CCS type filament supply. If I combine the 5V tap and the 6.3V tap for a total of 11.3VAC rms, I’ll have enough voltage to create a DC constant-current regulator. The regulator will consist of a diode bridge, input choke, filter capacitor, and constant-current regulator.
Here’s the question: do I apply 800mA across the parallel filaments? Generally, CCS regulators don’t like to be connected to parallel loads – uneven load balancing causes problems. The other solution is to make two 400mA CCS regulators for the individual filaments halves.
I suppose the other obvious solution is to make a 400mA CCS regulator for 12.6V, but then I’ll have to use yet another transformer.
I’m using a ECC99 from JJ Electronics. This tube has a split filament – two 6.3V heaters wired in 12.6V series (using 400mA). Generally, I’ll put the two in parallel and run the heaters using 800mA 6.3V (my transformer doesn’t have a 12.3V tap).
I want to change to a CCS type filament supply. If I combine the 5V tap and the 6.3V tap for a total of 11.3VAC rms, I’ll have enough voltage to create a DC constant-current regulator. The regulator will consist of a diode bridge, input choke, filter capacitor, and constant-current regulator.
Here’s the question: do I apply 800mA across the parallel filaments? Generally, CCS regulators don’t like to be connected to parallel loads – uneven load balancing causes problems. The other solution is to make two 400mA CCS regulators for the individual filaments halves.
I suppose the other obvious solution is to make a 400mA CCS regulator for 12.6V, but then I’ll have to use yet another transformer.
You're rather unlucky, you haven't got quite enough voltage to make a single 400mA CCS to feed the two heaters in series, so (as you suspected) your best option for CCS is to use two 400mA CCS, one for each half of the valve.
Hi,
If your xformer can supply sufficient juice, you could consider a voltage doubler then regulate both voltage and current to the required values.
Cheers,😉
If your xformer can supply sufficient juice, you could consider a voltage doubler then regulate both voltage and current to the required values.
Cheers,😉
I vote for adding the 5 and 6.3V windings, then using two 400mA current sources, one for each side. That way, each filament is assured of getting the proper heating. Otherwise you run the risk of one side hogging the current and getting warmer than the other.
In the real world, it's probably not that great of a problem, but if you're going to go to the trouble of running up a current source, then go ahead and do two. It won't be that much more money.
Grey
In the real world, it's probably not that great of a problem, but if you're going to go to the trouble of running up a current source, then go ahead and do two. It won't be that much more money.
Grey
I'm putting the tube on a circuit board, and I'm trying to keep AC power off the board. I could use voltage-regulated DC, but why not try CCS instead of voltage regulation?
Just looking for something new ...
Since this is a new design, I'm looking for a new transformer. Hammond doesn't have a 225-0-225 with a 12.3V tap. I need to start shopping around.
Just looking for something new ...
Since this is a new design, I'm looking for a new transformer. Hammond doesn't have a 225-0-225 with a 12.3V tap. I need to start shopping around.
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