I recently acquired this old tube amplifier from an estate sale, but have no idea how to tune it or test it as it does not appear to have the standard settings or knobs to tune. Any help would be greatly appreciated. Has 2 811-a and 2 3b28 tubes. Also, I'm assuming I need a vintage transmitter to key this without destroying the transmitter?
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how to tune this tube linear
- Thread starter swanny
- Start date
Wow! that thing looks like it has been around a while!! Military unit maybe?
Could ya post a pic of the inside and back by chance?....
Could ya post a pic of the inside and back by chance?....
As posted before need a picture of the inside, and also underneath the amp to see what type of circuits is in the amp.
It may or may not require external relay keying.
Get a good pic of the tank circuit and may be able to figure out what band it is designed for, or it may be multi band.
It may or may not require external relay keying.
Get a good pic of the tank circuit and may be able to figure out what band it is designed for, or it may be multi band.
Roller inductor looks like 10-80 meters.
Plate load cap is on the left, antenna tune is on the right,
Looks like tube type rectifiers.
I would be careful of just turning it on as those old filter caps may make a big BANG.
Still cant tell what or how it keys will need pic of under the chassis.
Plate load cap is on the left, antenna tune is on the right,
Looks like tube type rectifiers.
I would be careful of just turning it on as those old filter caps may make a big BANG.
Still cant tell what or how it keys will need pic of under the chassis.
OK on no bang.
Looks like it is direct rf input and output it would need either an external keying circuit or you can install one.
Notice the red cap going to the cathodes of the tubes? That is the Rf input
Output is the black color coax.
I also do not see any cathode bias or a relay to provide any bias.
Filament choke looks small, may just be the picture.
It could be upgraded and brought back to service. Would take some work, and if you plan on doing it yourself be very careful there is lethal voltages in that old amp.
Depending on the Plate transformer if there is a higher voltage tap on the secondary a pair of 572B's would be nice to put in that amp. Get rid of the tube rectifiers and use a full wave bridge.
20 years ago could find these old home brews at ham fests, back when ham fests were fun for the home brewer.
Thanks for the pictures.
Definitely old school.
Looks like it is direct rf input and output it would need either an external keying circuit or you can install one.
Notice the red cap going to the cathodes of the tubes? That is the Rf input
Output is the black color coax.
I also do not see any cathode bias or a relay to provide any bias.
Filament choke looks small, may just be the picture.
It could be upgraded and brought back to service. Would take some work, and if you plan on doing it yourself be very careful there is lethal voltages in that old amp.
Depending on the Plate transformer if there is a higher voltage tap on the secondary a pair of 572B's would be nice to put in that amp. Get rid of the tube rectifiers and use a full wave bridge.
20 years ago could find these old home brews at ham fests, back when ham fests were fun for the home brewer.
Thanks for the pictures.
Definitely old school.
wavrider,
what all would be needed to make the linear function correctly? How much drive would this require? Can you give specifics about the bias and relay? I would like to sell it, but I'm also drawn to tubes
so I may end up keeping it. What would the difference be in output if I put in the 572's? Again, thank you for your help.
what all would be needed to make the linear function correctly? How much drive would this require? Can you give specifics about the bias and relay? I would like to sell it, but I'm also drawn to tubes
so I may end up keeping it. What would the difference be in output if I put in the 572's? Again, thank you for your help.
it would work good on am or cw...not sure on ssb...the 811 tubes word be fine with max 25 rms or so...not sure what the other tubes are...the 572 might be to much for the others...the amp looks like a early collins to me...not sure...73 de JW
Just of the top of my head.
TR/RX relay, not hard to do. Voltages should all ready be there for the 12vdc relay. If you have a TP/DT relay the center pole can be used for the bias if the filament tr has a ct. If not then thee are other ways to make a cathode bias circuit.
You are only metering plate IP, I would also put in a Grid metering circuit.
811 are 150w output tubesm so 300 w is what you should expect out of that old home brew. Maybe a few more watts on 20 meters and lower.
If you can put in a pair of 572B's they are 300 watt tubes, so 600 watts is what you should get on 10 meters, give or take a few watts.
Most of what you need it there, just need to add a few more circuits.
Looking at the underneath of the chassis I see the two transformers, the chassis is cut so the wiring can be done.
The top view of the amp has a black TR right beside the filter caps, yet there is nothing cut out on the bottom of the chassis, is this maybe a huge choke? Swinging type?
I am not really up on the old AM type amplifiers but CK would know.
CK chime in on this one your the broadcast guy, could this old home brew been set up as a modulator for AM amp?
TR/RX relay, not hard to do. Voltages should all ready be there for the 12vdc relay. If you have a TP/DT relay the center pole can be used for the bias if the filament tr has a ct. If not then thee are other ways to make a cathode bias circuit.
You are only metering plate IP, I would also put in a Grid metering circuit.
811 are 150w output tubesm so 300 w is what you should expect out of that old home brew. Maybe a few more watts on 20 meters and lower.
If you can put in a pair of 572B's they are 300 watt tubes, so 600 watts is what you should get on 10 meters, give or take a few watts.
Most of what you need it there, just need to add a few more circuits.
Looking at the underneath of the chassis I see the two transformers, the chassis is cut so the wiring can be done.
The top view of the amp has a black TR right beside the filter caps, yet there is nothing cut out on the bottom of the chassis, is this maybe a huge choke? Swinging type?
I am not really up on the old AM type amplifiers but CK would know.
CK chime in on this one your the broadcast guy, could this old home brew been set up as a modulator for AM amp?
wavrider,
what all would be needed to make the linear function correctly? How much drive would this require? Can you give specifics about the bias and relay? I would like to sell it, but I'm also drawn to tubes
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.
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.
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