how to tune this tube linear

[wavrider]

R.T.F.F.

Post number 8 states if there is a higher voltage tap on the secondary of the hv tr then 572'bs would work.

The Tr looks like a multi tap secondary.

You aren't going to get twice the power out of 572Bs vs. 811As UNLESS the power supply says you can, and the rest of the circuit components agree.

If an amplifier is designed around 811As you CAN replace them with 572Bs. Just forget you made the change, treat the amplifier as if it had 811As, and it'll last a long time. It's doubtful that the "designer" allowed 100+% headroom into the power supply.

 

[swanny]

I believe the rest of the taps are lower voltage. I'm okay with the 300 out as i already had a new pair of 811's sitting around. I do need to research the keying circuit and bias and see if I can attempt to do those mods

 

[wavrider]

Should be able to find a heathkit sb-200 schematic and use it as a referance, of course you would not need to use 110vdc relays.

Or even the drake L4B would work for the keying and bias, you may need to change the zener value on the bias diode.

Drake L4B

This bias circuit should work, you may need only a 5v zener instead of the 8.5v

http://www.ameritron.com/pdffiles/AL-811H.pdf

Ameritron 811h manual

http://www.ameritron.com/pdffiles/AL-811.pdf

Three tube version using a string of diodes for bias.

Also there is no tuned input circuit for that home brew, If I am not mistaken and I could be going from memory your impedance should be around 100 ohms with a pair of 811, a quad will work well as it is around 50 ohms, the old hunter bandits use 4 572b"s no tuned input, those old amps scream.

good luck with the project and was hoping there were higher voltages on the B+ tr. MFJ sells the HV tr for the 572B's not to expensive if you do want to convert to that tube.

 

[Beetle]

R.T.F.F.

Post number 8 states if there is a higher voltage tap on the secondary of the hv tr then 572'bs would work.

The Tr looks like a multi tap secondary.

How much total power can the supply produce? Starting there, for every increase in voltage there will be a DEcrease in the amount of current the supply (transformer) will produce for ExI to equal P.

 

[Shockwave]

Just because you don't see a bias circuit on a tube amp does not suggest it can't be used on SSB or that the tubes will operate in class C as a transistor amp would without bias. Many tubes can be run with "zero bias" voltage and still run class AB1. If the plate voltage is not too high, the tubes will draw close to the correct idling current. Remember with most tubes the bias circuit is used to reduce bias current since maximum idling current would be achieved with zero bias. Also, as was mentioned this amp will have a 100 ohm input impedance with a pair of tubes. That's a 2:1 input VSWR. Most transistor rigs won't like this without a tuner.

 

[swanny]

okay, so I'm making some slight progress with the small amount of free time I have. I got a tuner, albeit one only rated at 300 watts, and I'm working on the keying relay idea. Couldn't I use a simple dc relay powered from a power supply with the rf out of the transmitter connected to the linear input rf through the relay? Is anything else needed?

 

[Shockwave]

The linear already has the required relay inside. You just need to figure out the easiest way to close the connections on the RCA jack on the back of the amp that is marked KEY when you transmit. Some use a foot pedal switch or push button if the radio does not have a key line.

 

[swanny]

there is no relay inside the linear or rca jack on the outside of the linear.

 

[Shockwave]

I'm sorry, for some reason I got my threads confused and thought we were talking about an Ameritron.

 

[swanny]

or do i need a keying circuit at all if it's direct rf in/out. Won't it just amplify the signal that's fed at the input?

 

[swanny]

lol well I learned something I should have thought of before. There is no receive through the linear I'm betting it was used with separate receiver/transmitter. Looks like I'll be spending some time reading the old copy of the Radio handbook I have or just get a bigger power supply for the transistor amp I already have.