Brit01 said:
You will have a greater range of choices later if you go with the 12.6 CT, rather than limit yourself with the 6.3.
It takes a while to understand all of the jumpers on JB's boards but keep looking at it, and all of a sudden you'll shout, Duh.....OK I get it.
Very good idea to ask questions prior to ordering a transformer.
A lot of us use a separate transformer for the heaters. Something to think about.
Ron
Been doing some reading and learning.
Now I understand that if I choose a CT transformer I would go for maybe 275-0-275 (550V). Is this providing 550 V in total?
But I'm a little confused if I choose a standard non center-tap what voltage I need.
So a winding with 275 Vac or double this?
I think I will go for 2 transformers as I want to use DC for the heaters and separate the B+ to the heater supply.
Had a lot of info and advice from forum friends regarding the voltage I need to get the correct output DC (12.6V).
Does this look right?
Full wave bridge:
Vdc = (Vac*1.414) - 2
12.6 Vdc = (10.3~ * 1.414) -2
Vdc out = 12.6~V
So:
Vac in = 10.3 ~ V winding
Also the Current confused me.
I need about 2.1-2.5A to supply the tubes (6N1P/5687).
Now the regulator LT1085 gives an output of about 2.5-3A max.
Now what will the input be?
Iout = Iac / 1.8
I need to provide 4.5 A from the secondary winding to get 2.5 A out?
2.5 = 4.5 / 1.8
😕 😕 😕 😕
Now I understand that if I choose a CT transformer I would go for maybe 275-0-275 (550V). Is this providing 550 V in total?
But I'm a little confused if I choose a standard non center-tap what voltage I need.
So a winding with 275 Vac or double this?
I think I will go for 2 transformers as I want to use DC for the heaters and separate the B+ to the heater supply.
Had a lot of info and advice from forum friends regarding the voltage I need to get the correct output DC (12.6V).
Does this look right?
Full wave bridge:
Vdc = (Vac*1.414) - 2
12.6 Vdc = (10.3~ * 1.414) -2
Vdc out = 12.6~V
So:
Vac in = 10.3 ~ V winding
Also the Current confused me.
I need about 2.1-2.5A to supply the tubes (6N1P/5687).
Now the regulator LT1085 gives an output of about 2.5-3A max.
Now what will the input be?
Iout = Iac / 1.8
I need to provide 4.5 A from the secondary winding to get 2.5 A out?
2.5 = 4.5 / 1.8
😕 😕 😕 😕
Chris,
What B+ voltage does John Broskie suggest for the boards?
With that figure it will be a lot easier to tell you how to go about building your psu.
What B+ voltage does John Broskie suggest for the boards?
With that figure it will be a lot easier to tell you how to go about building your psu.
Around 200-300V but better on the upper scale nearer 300.
Can I use a trimmer pot on the V regulator or do I need to calculate and use fixed resistors to set the output voltage?
Cheers
Brit01 said:
Correct! 300V is the recommended B+ target Voltage.
Yes you can use a trimmer / pot to adjust to your optimal voltage. Then turn off the circuit, let the caps drain and remove the pot and check what the resistance is set to and replace with a quality wirewound resistor and Voila! Set and good to go.
BTW, you do NOT have to have a 275V transformer to make the PS board output ~300V. My TX is 300-0-300 and I'm at ~294V with .66uF as the first cap. ( 2 .33uF in //) Bingo!
Be safe with that high voltage.....left hand in back pocket. 🙂
Ron
Can I feed the regulator with 4 A or will this overheat it? If I feed 2.5 A into it I will get out 2.5 amps?
Iout = Iac / 1.8
I'm confused with this part.
I see from the equation I lose a lot of current. Is this right??
That's a great tip. Might just try that.
I'll go for a 300V secondary then.
You can "overfeed" the regulator with Ampers, but it's the draw downstream that counts. The LT1085 is rated for 3A. If you draw 2.4 or so it will get hot, Make sure you use a good heatsink and you should be OK. Thermal paste ect.
About the secondaries, I only used the 300-0-300 because that's what I had. If you have yet to purchase a TX, then the recommended one is the 275-0-275. (gives you a larger first cap in the power supply) I have heard that a larger first cap will provide somewhat better base slam....(could be a rumor, in which case I'm sorry I'm spreading it)
Link to LT1085 datasheet
I'm only about 1/4 step ahead of you in learning this stuff...
Lots and Lots of reading. I almost understand some of Morgan Jones' books...LOL
Ron
About the secondaries, I only used the 300-0-300 because that's what I had. If you have yet to purchase a TX, then the recommended one is the 275-0-275. (gives you a larger first cap in the power supply) I have heard that a larger first cap will provide somewhat better base slam....(could be a rumor, in which case I'm sorry I'm spreading it)
Link to LT1085 datasheet
I'm only about 1/4 step ahead of you in learning this stuff...
Lots and Lots of reading. I almost understand some of Morgan Jones' books...LOL
Ron
Thanks for that Ron.
Now back to the heater supply.
If I use a CT and want 12.6 Vdc I'm thinking this is right:
Vdc = (Vac / 1.43) - Vdiode.
12.6 Vdc = (19.5 / 1.43) - 1
So I need a CT 9.75 -0- 9.75
Does this look correct?
Also I've heard pros and cons of CT verses non CT. Really I'm not sure what to go for.
Maybe CT can provide more Amps for the 4 heaters?
🙄 🙄 🙄
Now back to the heater supply.
If I use a CT and want 12.6 Vdc I'm thinking this is right:
Vdc = (Vac / 1.43) - Vdiode.
12.6 Vdc = (19.5 / 1.43) - 1
So I need a CT 9.75 -0- 9.75
Does this look correct?
Also I've heard pros and cons of CT verses non CT. Really I'm not sure what to go for.
Maybe CT can provide more Amps for the 4 heaters?
🙄 🙄 🙄
Most likely I'll get one built considering my location.
🙂 🙂 🙂 no worries dude. I know the feeling especially in my case where I wake up at 5am every day.
It's the regulation that complicates things a little. Peak loss/average loss/rms etc
Lots of factors to take into consideration.
Maybe I'm complicating things but want to get it right for the transformer windings.
On Bas's psu are you using 2W resistor for R4/R5?
Is this the min rating?
I have some 1/2W around the house. I assume these are going to overheat?
I can pick up some new 2W ones this week if recommended.
Is this the min rating?
I have some 1/2W around the house. I assume these are going to overheat?
I can pick up some new 2W ones this week if recommended.
I used the 1/2W for my R4 and R5...This is for the bias so it would reason that we are not dissipating a lot of watts here...
Fuses.
How, where and what type of fuse do I install for protection on the psu?
A mains fuse on the positive cable of the primary?
10 amps/ 5 amps?
Mains > fuse > trafo primary
btw this is my first project.
How, where and what type of fuse do I install for protection on the psu?
A mains fuse on the positive cable of the primary?
10 amps/ 5 amps?
Mains > fuse > trafo primary
btw this is my first project.
Also a question about C1 on Bas's psu.
I've got all Illinois electrolytic caps for the board. 47uF and 100uF.
Now is electrolytic ok for C1? What purpose does C1 have? Better with Polypropylene?
I've got some 47uF 630MPP1 red caps. Assume these are polys.
Also some 1uF RTI 450V coupling caps that I'm not going to use.
I want to use the Auricaps and PIO for the Aikido board.
I've got all Illinois electrolytic caps for the board. 47uF and 100uF.
Now is electrolytic ok for C1? What purpose does C1 have? Better with Polypropylene?
I've got some 47uF 630MPP1 red caps. Assume these are polys.
Also some 1uF RTI 450V coupling caps that I'm not going to use.
I want to use the Auricaps and PIO for the Aikido board.
Brit01,
"Now is electrolytic ok for C1? What purpose does C1 have? Better with Polypropylene?"
Yes, an electrolytic is appropriate for C1, as long as the voltage rating is not exceeded. (you should be fine)
Both the 47uF and the 100uF are (probably) too big. There are ratings for the size of the first cap (C1) after the toob rectumfrier. There are multiple posts about this topic in this thread. Re-reading old threads will cause you to understand things you did not comprehend earlier. (ask me how I know ,) )
Populate your board with everything except C1, place your 1uF cap in the C1 position and test your voltage at the output. Go ahead and hook it up to the Aikido being mindful of the lethal voltage you are working with. (You'll need to get the heaters working first!) It's reassuring to see them glow too. 😉
Do you have a Variac? if so use it to turn up the voltage slooooly, while watching for that magical blue smoke. Follow all safety rules with High Voltage!!
Fuses on the mains, I'd add up all of the amps you will be using on your build then add 1/2 amp to that. Slow Blow type. Yes the fuse goes before the turn on switch. You'll end up with somewhere around a 3.5A fuse in all likelyhood.
Ron
"Now is electrolytic ok for C1? What purpose does C1 have? Better with Polypropylene?"
Yes, an electrolytic is appropriate for C1, as long as the voltage rating is not exceeded. (you should be fine)
Both the 47uF and the 100uF are (probably) too big. There are ratings for the size of the first cap (C1) after the toob rectumfrier. There are multiple posts about this topic in this thread. Re-reading old threads will cause you to understand things you did not comprehend earlier. (ask me how I know ,) )
Populate your board with everything except C1, place your 1uF cap in the C1 position and test your voltage at the output. Go ahead and hook it up to the Aikido being mindful of the lethal voltage you are working with. (You'll need to get the heaters working first!) It's reassuring to see them glow too. 😉
Do you have a Variac? if so use it to turn up the voltage slooooly, while watching for that magical blue smoke. Follow all safety rules with High Voltage!!
Fuses on the mains, I'd add up all of the amps you will be using on your build then add 1/2 amp to that. Slow Blow type. Yes the fuse goes before the turn on switch. You'll end up with somewhere around a 3.5A fuse in all likelyhood.
Ron
I've got 47uF for C6/C4 as recommended.
Also got some 100uF Illinois caps for C2/C3.
All 450V.
Nope. Did think about this but I assume these are pricey.
I've got a light dimmer switch hanging around. Maybe I could incorporate this as a variac.
Same principal right?
I've heard that I need to connect the psu to a source to test it properly as it needs to be drawing a current.
Can I test the psu on its own?
I'm going to be using a 0-275 trafo. for the B+