Reverse Engineering leads from Tube amp

perfectdefect · 6th June 2011, 04:48 PM

Apologies if cross forum posts are frowned upon but I see a bunch of you reading here and this is right up your alley as it's a essentially a tube amplifier question and you may never look at the Musical Instruments section where I originally posted. A link to my original post: http://www.diyaudio.com/forums/music...h-hook-up.html

I need to reverse engineer the power and signal paths between a Clavioline and the 1950's tube instrument amp (Selmer or Gibson) the Keyboard was sold as a set with. The keyboard and amp are connected by a 6 pin 'umbilical' that supplies power to the preamp living in the keyboard and carries the instrument signal to the amp to be amplified and possibly some switching signals for effects in the amp. I'm guessing I need a transformer to power the preamp in the keyboard and the keyboard itself, as well as some misc components to allow me to plug the keyboard into a standard instrument amplifier via 1/4" jack.

Is it possible to figure out the power requirement for the preamp without a schematic for the keyboard? Schematics for the 'Gibson Clavioline Amplifier' can readily be found on line and it lists the transformer as a GA-40-P. I don't need this exact transformer as I don't have the amplifier to power, but perhaps it's a 2 stage parallel unit and I can get something that equals the stage that powers the preamp. I guess I'm looking for guidance beyond the thinking I've done.

Lots of pictures here: Clavioline - a set on Flickr

Help!

nightanole · 6th June 2011, 05:59 PM

If you can can give us the values of the resistors to the plates and cathodes we can give you a rough est of voltage and current.

perfectdefect · 6th June 2011, 06:21 PM

I'll check it out and post tonight. This is the resistors on the socket of the first tube in the series?

Are the 'Tiny Chief' cap's likely original?

Thanks.

perfectdefect · 6th June 2011, 07:11 PM

Pictures always help: Insides are pretty clean.

perfectdefect · 7th June 2011, 06:08 AM

Okay: resistors are old 4 band type. First tube socket in the tube series resistor goes from socket chassis to pin 6, is Gold - Green - Black - Red (200,000k?). No space between green and black. This is the only obvious resistor in the connector to first series tube leg. There is another connector lead that goes to a resistor and through some other stuff before going to this socket.

I guess a diagram is in order. Hopefully tomorrow.

6th June 2011, 04:48 PM	#1
perfectdefect diyAudio Member Join Date: Jun 2011	Reverse Engineering leads from Tube amp Apologies if cross forum posts are frowned upon but I see a bunch of you reading here and this is right up your alley as it's a essentially a tube amplifier question and you may never look at the Musical Instruments section where I originally posted. A link to my original post: http://www.diyaudio.com/forums/music...h-hook-up.html I need to reverse engineer the power and signal paths between a Clavioline and the 1950's tube instrument amp (Selmer or Gibson) the Keyboard was sold as a set with. The keyboard and amp are connected by a 6 pin 'umbilical' that supplies power to the preamp living in the keyboard and carries the instrument signal to the amp to be amplified and possibly some switching signals for effects in the amp. I'm guessing I need a transformer to power the preamp in the keyboard and the keyboard itself, as well as some misc components to allow me to plug the keyboard into a standard instrument amplifier via 1/4" jack. Is it possible to figure out the power requirement for the preamp without a schematic for the keyboard? Schematics for the 'Gibson Clavioline Amplifier' can readily be found on line and it lists the transformer as a GA-40-P. I don't need this exact transformer as I don't have the amplifier to power, but perhaps it's a 2 stage parallel unit and I can get something that equals the stage that powers the preamp. I guess I'm looking for guidance beyond the thinking I've done. Lots of pictures here: Clavioline - a set on Flickr Help!

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6th June 2011, 05:59 PM	#2
nightanole diyAudio Member Join Date: Feb 2009	If you can can give us the values of the resistors to the plates and cathodes we can give you a rough est of voltage and current.

6th June 2011, 06:21 PM	#3
perfectdefect diyAudio Member Join Date: Jun 2011	I'll check it out and post tonight. This is the resistors on the socket of the first tube in the series? Are the 'Tiny Chief' cap's likely original? Thanks.

7th June 2011, 06:08 AM	#5
perfectdefect diyAudio Member Join Date: Jun 2011	Okay: resistors are old 4 band type. First tube socket in the tube series resistor goes from socket chassis to pin 6, is Gold - Green - Black - Red (200,000k?). No space between green and black. This is the only obvious resistor in the connector to first series tube leg. There is another connector lead that goes to a resistor and through some other stuff before going to this socket. I guess a diagram is in order. Hopefully tomorrow.

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