Hello Steve from Dunnellon Florida. I was wondering if you could look at a Voltage Doubler board I am working on. I have a Drake L7 w/ 2 3-500Z Tubes and the orignal board Had a real bad voltage drop and the transformer was bad. I bought a new transformer with 240 input and 1850 vac out @ 2 amps. I tried the Harbach Board and it failed so I decided to build my own. I am very new at this but been around long enough to know that this will kill you. Anyway the other board I built by upgrading the caps, diodes, and bleeder resistors. I was getting 4200 volts without a load. However the voltage still would drop 400v when the amp was keyed. NOT GOOD ENOUGH. I was able to get 2600 watts output with the old board in the SSB mode and in the CW mode a peak of 1600 watts with 3200 volt rail. But this board I am building has double caps and diodes. Is there a way you could look at this layout for me. I have looked for your email address with no luck. If you would like to do this here is my email address. w4dra.dave@gmail.com . Thanks Dave
Hi Dave. I don't have an email address associated with this You Tube channel. There's not much point me emailing you I'm afraid. All voltage doublers have the sagging problem. I have never used a voltage doubler before and would be reluctant to use one in future as mine sags too much for my liking. You can 'stiffen' them up by reducing the value of the bleeder resistors across the capacitors. This will give a lower HT voltage simply by drawing some current and 'loading' the HT line. Then you have to select some resistors that can dissipate the heat this arrangement will generate. It will still be saggy though.
@@vk6cs456 I know some do but 500 volts is quite a bit. With the original doubler in amp it would drop 2-300v it was a .75 amp so I put a bigger transformer @2amp doubled the Caps Values and the number of caps. So now I have 16 caps 470uF 500 volt and upgraded the diodes to 16ea 1000v @ 6amps, 100K ohm across each cap. The transformer output is 1850vac. Sometimes I wish I had never even started it and just bought a new amplifier. But I always have liked a challenge even though I don't know a lot about it. So I guess that's why it's not called Professional Radio right.. Thanks Steve.
Amateur radio is all about trying things and learning. Unfortunately this is always the case with voltage doublers. This is because they present a higher impedance to the transformer. With voltage doublers the HT current goes through the capacitors, they're in series with the HT supply. The series resistance of the capacitors comes into play. Try to get some capacitors with the lowest ESR possible.
@@Vietnam_Vet_67 look at Richard Measures AG6K web page,last January SK....There you have everything on amplifiers,even calculating drop on voltage calculation by secondary resistance....but according to him 10 percent is normal....he wrote NEAR PERFECT AMPLIFIER for arrl handbook....
@@vk6cs456 yep,in doublers caps must have low esr and hi capacitance.....if secondary resistance is more than 15 ohms for 1200 volts secondary for doubler,you have problem...or more than 30 ohm for 2400 v secondary full bridge...or 40 ohms for 3200 secondary full bridge...according to calculation
Good video Steve. 👍
didn't see any meatballs Steve, keep up the interesting projects.
Hi Steve, Great progress. The soft start is also good for the filament so without high inrush, they will last longer.
Greets Frank.
Thanks Frank. A few people have suggested that. Maybe I'll give it some thought.
Hello Steve from Dunnellon Florida. I was wondering if you could look at a Voltage Doubler board I am working on. I have a Drake L7 w/ 2 3-500Z Tubes and the orignal board Had a real bad voltage drop and the transformer was bad. I bought a new transformer with 240 input and 1850 vac out @ 2 amps. I tried the Harbach Board and it failed so I decided to build my own. I am very new at this but been around long enough to know that this will kill you. Anyway the other board I built by upgrading the caps, diodes, and bleeder resistors. I was getting 4200 volts without a load. However the voltage still would drop 400v when the amp was keyed. NOT GOOD ENOUGH. I was able to get 2600 watts output with the old board in the SSB mode and in the CW mode a peak of 1600 watts with 3200 volt rail. But this board I am building has double caps and diodes.
Is there a way you could look at this layout for me. I have looked for your email address with no luck. If you would like to do this here is my email address. w4dra.dave@gmail.com .
Thanks
Dave
Hi Dave. I don't have an email address associated with this You Tube channel. There's not much point me emailing you I'm afraid. All voltage doublers have the sagging problem. I have never used a voltage doubler before and would be reluctant to use one in future as mine sags too much for my liking. You can 'stiffen' them up by reducing the value of the bleeder resistors across the capacitors. This will give a lower HT voltage simply by drawing some current and 'loading' the HT line. Then you have to select some resistors that can dissipate the heat this arrangement will generate. It will still be saggy though.
@@vk6cs456 I know some do but 500 volts is quite a bit. With the original doubler in amp it would drop 2-300v it was a .75 amp so I put a bigger transformer @2amp doubled the Caps Values and the number of caps. So now I have 16 caps 470uF 500 volt and upgraded the diodes to 16ea 1000v @ 6amps, 100K ohm across each cap. The transformer output is 1850vac.
Sometimes I wish I had never even started it and just bought a new amplifier. But I always have liked a challenge even though I don't know a lot about it. So I guess that's why it's not called Professional Radio right..
Thanks Steve.
Amateur radio is all about trying things and learning. Unfortunately this is always the case with voltage doublers. This is because they present a higher impedance to the transformer. With voltage doublers the HT current goes through the capacitors, they're in series with the HT supply. The series resistance of the capacitors comes into play. Try to get some capacitors with the lowest ESR possible.
@@Vietnam_Vet_67 look at Richard Measures AG6K web page,last January SK....There you have everything on amplifiers,even calculating drop on voltage calculation by secondary resistance....but according to him 10 percent is normal....he wrote NEAR PERFECT AMPLIFIER for arrl handbook....
@@vk6cs456 yep,in doublers caps must have low esr and hi capacitance.....if secondary resistance is more than 15 ohms for 1200 volts secondary for doubler,you have problem...or more than 30 ohm for 2400 v secondary full bridge...or 40 ohms for 3200 secondary full bridge...according to calculation
on it goes...
Yes it does. I want to get this bloody thing finished.
Amateur Hour with another VK6 Numpty who has NO IDEA what he's doing !
Not to mention he is touching mains voltage without an Electrical Licence.