converting old phono tube amp to guitar amp or keep as is?

[vegas]

Hi,

I found an old Shelburn phono/radio cabinet model rst 200 and took out the tube amp.
the tube layout in the cabinet indicates:
(1) 12ax7 tube
(2) 35C5 tubes
(1) 12 BA6 tube
(1) 12 BE6 tube

Filter(cap )
1st IF
2nd IF


the wires were partially hacked out already so I don't know where they go to/came from and I read that it can be dangerous to work with these.
im guessing the 2 sets of brown wires were going to the speakers in the cabinet? (they look like speaker cables )also lead to transformer
the grey wires at the back go into the radio/mono/stereo switch (Im guessing these were from phono player? source signal cables?
the brown wire at the back goes to the off switch (power)?
I dont know if it works , can someone offer advice?

cheers

[olddawg]

Hi,

I found an old Shelburn phono/radio cabinet model rst 200 and took out the tube amp.
the tube layout in the cabinet indicates:
(1) 12ax7 tube
(2) 35C5 tubes
(1) 12 BA6 tube
(1) 12 BE6 tube

Filter(cap )
1st IF
2nd IF


the wires were partially hacked out already so I don't know where they go to/came from and I read that it can be dangerous to work with these.
im guessing the 2 sets of brown wires were going to the speakers in the cabinet? (they look like speaker cables )also lead to transformer
the grey wires at the back go into the radio/mono/stereo switch (Im guessing these were from phono player? source signal cables?
the brown wire at the back goes to the off switch (power)?
I dont know if it works , can someone offer advice?

cheers

That is a series filament amplifier with no power transformer. It is not a good candidate for conversion. it is also stereo. You could probably use the the output transformers to make two single ended 5 watt amps and the 12AX7. That's about it IMHO. It has a hot chassis and could be dangerous if used.

[vegas]

amp

Hi,

Thanks for that response. Could I just attach cables to it and use it as a regular tube phono amp without harm?
Im trying to determine what cables are for power, signal/source, speakers etc. as it wasn't connected to anything when I got it.
pardon my newbiness
Cheers

[vegas]

conversion?

also,

how would I go about making it 2 singles ended amps with the transformers?
any resources I can read up on?

[hasserl]

Well you could add an isolation transformer and wire it up correctly with a proper ground, and then it would be no more dangerous than any other properly wired amp.

[olddawg]

Well you could add an isolation transformer and wire it up correctly with a proper ground, and then it would be no more dangerous than any other properly wired amp.

Yeah you could use a 1:1 isolation transformer. And you could build a stereo guitar amp. But why? You will probably have to add a tube or two so the series filament configuration will not work and you will have to buy a power transformer anyway. And...you probably will want to use different power tubes. You could use it as a phono amp but you need to find the original schematic. My guess is that it used an ugly old high output ceramic cartridge. If you converted it to line input it will require circuit changes dealing with the RIAA equalization gain , etc. If you use a more modern magneteic cartridge, you will have to use a phone preamp. IMHO it is more trouble than it is worth. If want to build a low wattage guitar amp, build one with the right parts. Otherwise you risk wasting a lot of time and frustration.

[vegas]

amp

ok....thanks for the input.

Old dawg-you mentioned that you would use each transformer for seperate amps and use the tube.-i guess build 1 amp with one of the 2 transformers and use/scrap the rest of the parts/chasis

[olddawg]

ok....thanks for the input.

Old dawg-you mentioned that you would use each transformer for seperate amps and use the tube.-i guess build 1 amp with one of the 2 transformers and use/scrap the rest of the parts/chasis

The OTs would probably work for two single ended amps using an EL84 or a 6V6. There are more experienced persons on this board thet could tell you exactly. I have no idea how musical they would sound. Personally, I would just buy a Epiphone Valve Jr for around $100 and skip the headache.

[roughcut studios]

old phono amp

It looks like one of the output transformers is missing it's secondary leads. The photos show one output tranny with enameled wires going to a terminal strip. There should be leads like that on the other one too, maybe they got broken off right at the paper wrap level. look closely. You may be able to graft new leads onto the stubs and salvage the transformer. Please don't use this amp for guitar or harp without an isolation transformer because of the shock hazard.
...........Jon

[hasserl]

And you could build a stereo guitar amp. But why?

There's several uses. Stereo ouput into two cabs, makes for a very nice spread of sound. Make a wet/dry setup in a single amp with one power amp running dry and run reverb on the other. You could even take a sample of the output of the dry, run it thru a reverb tank and out to the second channel as your wet mix. That way all your distortion is done in the dry section and the reverb is added post distortion. There is plenty of preamp tubes available for doing this. Or it would make an easy way to have a half power setting, lift the cathode of one power tube and cut the output in half.

You're only limited by your imagination, get out of the box once in awhile.

[olddawg]

There's several uses. Stereo ouput into two cabs, makes for a very nice spread of sound. Make a wet/dry setup in a single amp with one power amp running dry and run reverb on the other. You could even take a sample of the output of the dry, run it thru a reverb tank and out to the second channel as your wet mix. That way all your distortion is done in the dry section and the reverb is added post distortion. There is plenty of preamp tubes available for doing this. Or it would make an easy way to have a half power setting, lift the cathode of one power tube and cut the output in half.

You're only limited by your imagination, get out of the box once in awhile.

Of course I know why in this sense. I own a couple of stereo amps and my current stage rig uses two amps and an A/B/Y setup. I asked "why" because of the cost/headache/benefit balance of trying to resurrect this old POS into a usable guitar amp, expecially for someone who is new to it. It is better to start off with a working amp and mod it, or buy a kit for most people as a first build.

[vegas]

tube mic/instrument preamp

thanks for the replies...how about converting this to a mic /instrument tube preamp say for a rhodes?? posssible? how difficult?