Which tubes may be good for what section of the amp? 
What limits will I have for converting?
Having a Johnson Messenger with 9 different tubes, turning this into a guitar amp. Searching and reading everyone's posts, to see which direction I am going for. I'd like to start of with a small preamp and power amp design. I do know the cb was 6 volt, 12 volt and ac powered.
I now have another tubed CB to use, Gemtronics GTX 2300, which I'll need shematic for and figure the different tubes being used.
Tubes I have to use are: 6BA6, 6BE6, 7061, 6BJ6, 6JD6, 6AW8A, 7025, 12AB5, 12AX7 and, 12BA6, from the Messenger.
The reason I am needing this, is because my Crate TD35
needs repaired and I'm not happy with the Solid State for the power amp. The good part is, I'm not rushing into a quick build. but rather a nice all tube sound. Starting with building a small tube amp, is my 1st goal. Building next stage up is later.
Thank you for your input.
What limits will I have for converting?
Having a Johnson Messenger with 9 different tubes, turning this into a guitar amp. Searching and reading everyone's posts, to see which direction I am going for. I'd like to start of with a small preamp and power amp design. I do know the cb was 6 volt, 12 volt and ac powered.
I now have another tubed CB to use, Gemtronics GTX 2300, which I'll need shematic for and figure the different tubes being used.
Tubes I have to use are: 6BA6, 6BE6, 7061, 6BJ6, 6JD6, 6AW8A, 7025, 12AB5, 12AX7 and, 12BA6, from the Messenger.
The reason I am needing this, is because my Crate TD35
needs repaired and I'm not happy with the Solid State for the power amp. The good part is, I'm not rushing into a quick build. but rather a nice all tube sound. Starting with building a small tube amp, is my 1st goal. Building next stage up is later.Thank you for your input.
Almost all of the circuitry in these units are for the RF signals,not audio signal amplification. You could salvage the 12AX7 and 7025 for preamp tubes. The 12AB5 is probably the output tube, good for about 10 watts so that will be OK for your output power. The 7061 is also a power tube, so I don't know what is going on there.
These really don't lend themselves to change into audio amps as most of the circuitry is for RF broadcast and reception so the component values are for radio frequency. It will be hard to design the power supply because you might not know what current your power transformer will supply for each section, 6 volt, high voltage, etc. The tubes themselves could be used to amplify audio, it's just that the circuits are not designed for audio frequencies until the output section, so the components will all need to be changed for audio. You might as well start from scratch.
These really don't lend themselves to change into audio amps as most of the circuitry is for RF broadcast and reception so the component values are for radio frequency. It will be hard to design the power supply because you might not know what current your power transformer will supply for each section, 6 volt, high voltage, etc. The tubes themselves could be used to amplify audio, it's just that the circuits are not designed for audio frequencies until the output section, so the components will all need to be changed for audio. You might as well start from scratch.
if you dont mind a guess, id say the7061 was audio output and the 12ab5 was Rf output, new one of them ham radio fellers was who using 6v6's as Rf output.
Agreed,the 7061 very likely could be but audio output,but still the 12AB5 could still be used for 11-12 watts of ouptut power in the new amp.,We're just guessing without a schemo. The main problem to be solved is to convert it to audio frequency from RF signals and to re-design the circuit and power supply. The 12AB5 could also be used as a limiter as well for the radio receiver. We need a schematic.
Excellent work, okcrum! So, from the mic or the ECC82 tube, which is a low gain tube, over to the 12AB5 is the only part of the unit that works in the audio frequency range. Looks like a lot of work for a pretty small output amp. I'm not sure if you can sub in an ECC83 for the ECC82 or not. If you can, at least you will get more preamp signal. You would have to re-bias the tube.
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Thank you for the responses. I know I'd have to redesign and rewire one of them. I do have the schematic for one of them, so I know the wiring for power supply.
View attachment messenger_2_sch.pdf
The Gemtronics will most likely be disassembled
The Gemtronics will most likely be disassembled
OK for a simple project, and making a low power guitar amp - but it's not really 'modifying' - more like ripping everything out and reusing a small number of parts (mostly 2 or 3 valves and the mains transformer).
True. For the power to the tubes, can be saved. wether 6.3v or 12v. Everything else will be removed or rewired.
The Gemtronic tubes are 6BL8, 6GH8, 7189, 12AT7, 6BA6, 6GH8, 6BL8, 6BQ5, 6BA6, 12AX7, 6BA6. I may start on this one first. More room to have available. Low on cash, makes this a low budget project. So, I have over 20 tubes to choose from. I believe I have enough to use, to start out a small guitar amp and build it up from there.
Plenty of options is better then 1 option. I'll see where this may go
Plenty of options is better then 1 option. I'll see where this may go
7189 is the exact same tube as 6BQ5 except is rated for 400 volts plate. It's a heavy duty 6BQ5. The 12AT7 could be good for your phase inverter, so you are on your way to an 18watt push-pull amp. You just need the trannies and power supply.
1. 12AX7, two stages into 12AT7 PI, 6BQ5,7189 output.
2. djgibson's idea, 6AW8 triode/pentode preamp, 12AT7 PI, same power tubes.
The 6GH8 will also serve the same purpose as the 6AW8 with slightly less gain for the triode.
The triode in the 6AW8 has amplification factor the same as a 5751. The 6GH8 triode's is the same as a 12AY7.
You also have a 7025 which is a better version of a 12AX7. Same difference as the 6BQ5 to the 7189, so if you want, you have enough for 4 12AX7 stages. You have many possibilities.
1. 12AX7, two stages into 12AT7 PI, 6BQ5,7189 output.
2. djgibson's idea, 6AW8 triode/pentode preamp, 12AT7 PI, same power tubes.
The 6GH8 will also serve the same purpose as the 6AW8 with slightly less gain for the triode.
The triode in the 6AW8 has amplification factor the same as a 5751. The 6GH8 triode's is the same as a 12AY7.
You also have a 7025 which is a better version of a 12AX7. Same difference as the 6BQ5 to the 7189, so if you want, you have enough for 4 12AX7 stages. You have many possibilities.
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6aw8a will make a lovely triode into pentode preamp
Humm could you elaborate a bit more ?
tv video tube 6aw8a for audio preamp ?You could use the pentode section for the preamp, just watch out for lower plate voltage, 150v. It is a sharp cutoff pentode and can be used for audio frequencies as well as RF. This could be similar to an EF86 input stage in the Vox AC15 or 30 when they used pentodes. You just need to figure out biasing the tube properly. I don't know how it will sound but sometimes it might be worth a try. Why keep building the same amps over and over? Fender 5E3 Deluxes are great, but how many of them and their copies have been built?
And the triode section could be used for a cathodyne phase inverter or a gain recovery stage after the tone stack. It has an amplification factor of 70 which is the same as a 5751.
Or as djgibson said, input the amp into the triode section and then into the pentode. This probably is less noisy because the pentodes tend to be noisier, so if it is second in the signal chain, the noise it generates will be less because all signal and noise at the input will be louder since it is amplified more times.
Here's the data sheet: http://www.tubebooks.org/tubedata/HB-3/Receiving_Tubes_Part_1/6AW8-A.PDF
And the triode section could be used for a cathodyne phase inverter or a gain recovery stage after the tone stack. It has an amplification factor of 70 which is the same as a 5751.
Or as djgibson said, input the amp into the triode section and then into the pentode. This probably is less noisy because the pentodes tend to be noisier, so if it is second in the signal chain, the noise it generates will be less because all signal and noise at the input will be louder since it is amplified more times.
Here's the data sheet: http://www.tubebooks.org/tubedata/HB-3/Receiving_Tubes_Part_1/6AW8-A.PDF
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I did a little more research and found this. I have a McGohan PA amp I rebuilt an it has a 6AU6 input but the data sheet says RF and IF duty, but handles audio freq. nice. Just have to find one that isn't noisy. http://www.mif.pg.gda.pl/homepages/frank/sheets/093/6/6AU6A.pdf
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