Funny you should ask. Moved to the double diode version NL606 and this cured all the RFI issues.
And yes, my input choke is right about 5H. How did you guess? 🙂
And yes, my input choke is right about 5H. How did you guess? 🙂
Didn't have to guess the choke size or even calc it. I cheated & simply read it off the graph of one of the common 5V heater rectifiers, published in many of the RCA tube manuals.😀
PRR, I apologize. You are right of course with respect to current flow.
I came up with another schematic which hopefully works and eliminates the AC component by creating an artificial CT.
3 — ImgBB
I know it sounds like I am not being serious about this proposal given the lack of details, but please bear with me. Hopefully you won't be disappointed with the end result.
The final result will be on par with my other creations (fingers crossed).
833-12ax7-307-A — ImgBB
12ax7-e-307-A — ImgBB
I have larger amps but these are by far my favorite.
Edit: in order to balance the 575A could I parallel some precision resistors (e.g. 25ohm 1% 50W) such as PWR221T-50-25R0F Bourns | Mouser Italia to both filaments? I would end up with an additional 50ohm (almost) negligible load on top of main filament power draw.
image — ImgBB
I came up with another schematic which hopefully works and eliminates the AC component by creating an artificial CT.
3 — ImgBB
I know it sounds like I am not being serious about this proposal given the lack of details, but please bear with me. Hopefully you won't be disappointed with the end result.
The final result will be on par with my other creations (fingers crossed).
833-12ax7-307-A — ImgBB
12ax7-e-307-A — ImgBB
I have larger amps but these are by far my favorite.
Edit: in order to balance the 575A could I parallel some precision resistors (e.g. 25ohm 1% 50W) such as PWR221T-50-25R0F Bourns | Mouser Italia to both filaments? I would end up with an additional 50ohm (almost) negligible load on top of main filament power draw.
image — ImgBB
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This last idea will also not work. Why insist on complicating things when you have been given a perfectly workable solution in #10?
Because it doesn't eliminate the AC component as a CT tapped transformer would.
I don't understand why the last solution won't work...
I don't understand why the last solution won't work...
With 1 ohm resistors, it should work really well. In practical terms, it would suck horribly.
So the issue is the balance between the two 575A filaments? Would it work without resistors?
I apologize if these seem stupid questions but I honestly want to learn more in the process...
I apologize if these seem stupid questions but I honestly want to learn more in the process...
Let's say the cold resistance of one 575A is 0.05 ohms and the other is 0.025 ohms and we'll assume that your 10V transformer provides approximately unlimited current. At startup, how will the voltage be distributed?
Looking more carefully at the numbers, 1 ohm balancing resistors probably aren't low enough, I'd go for 0.5 ohm resistors. These would need to be rated for 150W each.
Looking more carefully at the numbers, 1 ohm balancing resistors probably aren't low enough, I'd go for 0.5 ohm resistors. These would need to be rated for 150W each.
Right, I understand but the same logic would apply to schematic in post #10, or am I not getting the whole picture?
This is an extremely simple setup to connect and test. It only takes a few minutes and can save hours of pointless discussions.
I have yet to see a 10 volt 10 amp filament transformer insulated for the kilovolts a DC supply for a 833A or other transmitting tube requires. UTC built a transformer (p/n S-60, CG-121. LS-83, etc.) with 5 v 20 amp secondary insulation minimum 10,000 volts. The 10 volt 10 amp transformers were insulated for 1500 volts, which would arc over immediately at the voltages a 833A operates at.... Just be careful...
Yeah, I have one 2.5V/10A transformer with something like 10kV of insulation. They are very rare.
Try the series heater supply connexion B4 any HT is applied. Check the heater voltages after a couple of minutes, with luck they will be the same. Otherwise start looking for the resistance required to equalize.🙂
Yesterday got the wiring done to start testing within the chassis. Just to clarify, the 833A has nothing to do with the 575A rectifiers. Also, the B+ (1600v) in my 833A is taken from a solid state bridge to RCRC arrangement so no tubes (and no filament xformers) were involved.
My current 575A will not see anything like 10KV..
My current 575A will not see anything like 10KV..
So, i did some testing with interesting results. First and foremost, the transformers sag when powered at 115v. I end up with 4.2v at the base of the 575A which is far too low for safe operation. That said, parallel secondaries work fine and there is balance between the rectifier filaments. Secondaries in series display a voltage imbalance which, again, is not acceptable as the filaments do not heat up correctly.
At this point I believe a custom transformer would be the best bet. Any cheap manufacturer of toroidal xformers in Europe?
Thanks!
At this point I believe a custom transformer would be the best bet. Any cheap manufacturer of toroidal xformers in Europe?
Thanks!
