Ok, my last thread was closed, due to my asking for help to do something extremely dangerous or illegal (converting an old intercom to a guitar amplifier). I 100% want to make sure I don’t harm myself or anyone else, so is there any value or danger in disassembling the old unit, salvaging some of the components and building a simple amp using that chassis? It already has tube sockets...
Obviously I would need to acquire the proper transformers and other parts.
Obviously I would need to acquire the proper transformers and other parts.
It is a piece of metal. They are parts. Danger is in the system, not the individual parts you use.
The danger with using a chassis like you have is that you might not use an isolation transformer. Mind you, maybe there might be a concern that someone will see the example of a working circuit and then try reproducing it without an isolation transformer. Mind you, you can get into lethal voltage-current territory on the 'safe' side of the isolation transformer.
The big concern is a uninitiated person working with a circuit that can be unsafe. I would have my own thread shut down given the circuit even though I have the skill set to work on it safely. My thoughts on you and your chassis was to determine what you had to work with as far as parts and then strip the chassis of parts and build up a simple guitar amp.
The concern about the health of the tubes is a valid one, with the unit that may be left on at all times. So, the real 'good' part is the output transformer (OT). Tubes can be replaced easy enough and cheaply if you live in the US. The OT dictates that you use a tube that runs between 100-200V. It has a primary (winding) impedance around 2-3k ohms with the same speaker impedance. There are a host of tubes that can run into it.
The next question I was going to ask was if you could unsolder one lead to the speaker and measure the resistance, or if the speaker might have its impedance printed on it. If the speaker has a low impedance of , say 4 ohm, you could use an 8 ohm speaker (more common), and the transformer being a transformative device, end up with a primary impedance of 4-6k. Which works for a different range of tube types, one in mind is the 6AQ5, 12AQ5 (first number it the heater voltage). Not being constrained by the 35C5 tube you can run all the tubes heaters in parallel at 6 or 12V. You would still need a high voltage transformer, most sold for tube work have a 6V winding for the heaters.
The rest of the parts on the chassis are of little value, the electrolytic capacitor (the big red one) has seen it's length of years, I would not reuse it. The other resistor and capacitors are of minimal cost it is not a bad idea getting new as you do not need the headache of questionable parts when starting out. If you want to strip the chassis I would get what is called a solder sucker. Also what potentiometer value do you have, disconnect and measure across the end lugs.
The big concern is a uninitiated person working with a circuit that can be unsafe. I would have my own thread shut down given the circuit even though I have the skill set to work on it safely. My thoughts on you and your chassis was to determine what you had to work with as far as parts and then strip the chassis of parts and build up a simple guitar amp.
The concern about the health of the tubes is a valid one, with the unit that may be left on at all times. So, the real 'good' part is the output transformer (OT). Tubes can be replaced easy enough and cheaply if you live in the US. The OT dictates that you use a tube that runs between 100-200V. It has a primary (winding) impedance around 2-3k ohms with the same speaker impedance. There are a host of tubes that can run into it.
The next question I was going to ask was if you could unsolder one lead to the speaker and measure the resistance, or if the speaker might have its impedance printed on it. If the speaker has a low impedance of , say 4 ohm, you could use an 8 ohm speaker (more common), and the transformer being a transformative device, end up with a primary impedance of 4-6k. Which works for a different range of tube types, one in mind is the 6AQ5, 12AQ5 (first number it the heater voltage). Not being constrained by the 35C5 tube you can run all the tubes heaters in parallel at 6 or 12V. You would still need a high voltage transformer, most sold for tube work have a 6V winding for the heaters.
The rest of the parts on the chassis are of little value, the electrolytic capacitor (the big red one) has seen it's length of years, I would not reuse it. The other resistor and capacitors are of minimal cost it is not a bad idea getting new as you do not need the headache of questionable parts when starting out. If you want to strip the chassis I would get what is called a solder sucker. Also what potentiometer value do you have, disconnect and measure across the end lugs.
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Thanks Printer 2.
I’ll check out the speaker. Do I have to fear for my life poking around in this thing? I don’t plan on connecting power to it ever at this point.
I’ll check out the speaker. Do I have to fear for my life poking around in this thing? I don’t plan on connecting power to it ever at this point.
You're safe as long as it hasn't been plugged in recently (to be sure, let a few days elapse after plugging in, and before touching anything.)
Please do Google stuff about tube safety - many DIY forums will have "sticky" posts on this. You have much better odds of remaining unscathed working on a tube project if you have a pretty good understanding of electricity, and the dangers it poses.
-Gnobuddy
Sage advice. A good place to start is Rob Robinette's Safety article
but it's only one of many out there.