Thanks Raindance!
I saw both schematics. You have 320 Vdc on B+, whereas I have 375 Vdc. I think the power transformer is now 300V instead of the first kits with 260V.
You also have 20 V on the cathode of the 6P3P and I have 25 - 26 V.
I saw both schematics. You have 320 Vdc on B+, whereas I have 375 Vdc. I think the power transformer is now 300V instead of the first kits with 260V.
You also have 20 V on the cathode of the 6P3P and I have 25 - 26 V.
I use a 120 volt to 110 volt step down transformer. But I don't think the voltages even started that high. Wow.
How about adding another RC filter stage after the choke? That will help throw away some voltage.
Also the 5Z4 has a drop of 20 volts. A 5Y3 is 60 volts. That's another path ��
You'd need to verify pinout.
You'd need to verify pinout.
My measurements today:
mains voltage 123 volts.
Output of rectifier 358 volts
After choke 345 volts
Plate to cathode voltage 300 volts
Cathode resistor voltage 20/23 volts (tubes aren't matched)
Using this calculator my bias is roughly 66mA which is ideal for either EL34 or 6P3P.
Weber Bias Calculator
Don't forget that there is current flowing through the screen.
mains voltage 123 volts.
Output of rectifier 358 volts
After choke 345 volts
Plate to cathode voltage 300 volts
Cathode resistor voltage 20/23 volts (tubes aren't matched)
Using this calculator my bias is roughly 66mA which is ideal for either EL34 or 6P3P.
Weber Bias Calculator
Don't forget that there is current flowing through the screen.
measure bias thru the cathode resistor, the current determined x plate voltage equals tube input power...
What if I take the first cap off and make the psu with a choke input? Would this drop the voltage at the 330uF cap after the choke?
I would not do that. Inductor input filters are only good with circuits that draw a small fixed amount of current (not power amplifiers). It will exhibit poor filtering performance as soon as you draw more current.
By the way, my secondary winding is also marked 300 volts. Adding another RC element to the power supply seems like the best bet followed by changing to a rectifier that drops a few more volts.
What rectifier did yours come with? Is it a 5Z4P?
By the way, my secondary winding is also marked 300 volts. Adding another RC element to the power supply seems like the best bet followed by changing to a rectifier that drops a few more volts.
What rectifier did yours come with? Is it a 5Z4P?
What if I take the first cap off and make the psu with a choke input? Would this drop the voltage at the 330uF cap after the choke?
try it out and tell us what happens next...voltage will be lower....
I got also a 5Z4P. I have an old Siemens GZ34 on the bench, but voltage drop is lower than the 5Z4P,so it is not a solution. I will probably try the RC filter approach.
In the meanwhile something got wrong, the sound became too low and distorted. Not sure why, but I had a nasty noise under the wood after installing the ground resistors in the 6P3P tubes heaters. Nothing seems burned, took out the resistors and everything was fine. Now it started to distort. Any clues of what happened?
In the meanwhile something got wrong, the sound became too low and distorted. Not sure why, but I had a nasty noise under the wood after installing the ground resistors in the 6P3P tubes heaters. Nothing seems burned, took out the resistors and everything was fine. Now it started to distort. Any clues of what happened?
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Schematic:
Pictures:
An externally hosted image should be here but it was not working when we last tested it.
Pictures:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Actually, rethinking my previous response - I agree with AJT - it is worth trying. With the high level of class A bias it is a fairly constant current draw and will help throw away a few volts..
Not sure how to put the image appearing here, I inserted the url's as supposed...
Here go the links:
https://www.flickr.com/photos/143822745@N08/28047505481/in/dateposted-public/
https://www.flickr.com/photos/143822745@N08/27510261483/in/dateposted-public/
https://www.flickr.com/photos/143822745@N08/28091356156/in/dateposted-public/
https://www.flickr.com/photos/143822745@N08/27510259183/in/dateposted-public/
Here go the links:
https://www.flickr.com/photos/143822745@N08/28047505481/in/dateposted-public/
https://www.flickr.com/photos/143822745@N08/27510261483/in/dateposted-public/
https://www.flickr.com/photos/143822745@N08/28091356156/in/dateposted-public/
https://www.flickr.com/photos/143822745@N08/27510259183/in/dateposted-public/
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