I have recently acquired an old guitar tube amplifier. Looks like it was built sometime in 60s so it plugs directly to the AC outlet (no power or isolation transformer). All parts and tubes are there but given the age, I am afraid to even plug it into the wall to check if it is working.
I know that first, I would have to add isolation transformer and convert the cable to three prong so it is properly grounded. My skills are very basic but I think with some help I could pull that off. My question is, looking at the schematic, can you tell me if it is even worth to work on this amplifier? Isolation trafo, capacitors, diodes, etc would probably cost more than the amp is worth. The only reason for me to work on this amp would be to move it to a new case to reduce the size and have a tube guitar amp so I can compare the sound with my solid state amplifier.
Here is the schematic: picture
If I decide to work on the amp, I would remove the tremolo circuit on the right (12AV6 tube) as I do not need it.
Thanks.
I know that first, I would have to add isolation transformer and convert the cable to three prong so it is properly grounded. My skills are very basic but I think with some help I could pull that off. My question is, looking at the schematic, can you tell me if it is even worth to work on this amplifier? Isolation trafo, capacitors, diodes, etc would probably cost more than the amp is worth. The only reason for me to work on this amp would be to move it to a new case to reduce the size and have a tube guitar amp so I can compare the sound with my solid state amplifier.
Here is the schematic: picture
If I decide to work on the amp, I would remove the tremolo circuit on the right (12AV6 tube) as I do not need it.
Thanks.
Yes an isolation transformer is absolutely required, and at a minimum you would need to replace the electrolytic caps, rectifier (1N4007 will do fine) and probably the coupling cap to the 50C5.
I wouldn't do anything beyond this, and since a series filament string is used the simplest thing to do is just ignore the tremolo circuit, removing it would require a new power resistor in the filament string.
Listen to it, and decide if it is worth any more trouble than this. It might make interesting tone or not...
I wouldn't do anything beyond this, and since a series filament string is used the simplest thing to do is just ignore the tremolo circuit, removing it would require a new power resistor in the filament string.
Listen to it, and decide if it is worth any more trouble than this. It might make interesting tone or not...
Yeah, that's pretty primitive. Half wave silicon rectifier, you can't remove the tremolo without rejigging the heater circuit, it needs an isolation transformer. >=55VA
Unless someone recognises it as being of historical interest, I don't think it's worth the effort and money.
Every guitarist should have a tube amp sometime. Build a Fender Champ.
w
Unless someone recognises it as being of historical interest, I don't think it's worth the effort and money.
Every guitarist should have a tube amp sometime. Build a Fender Champ.
w
Well, let's not get too excited here....
As long as you don't go grabbing other electrical gear (like a metal mic connected to another PA amp without a safety ground) with sweaty hands or in a rainstorm you can't kill yourself with an amp like this.
But cobbling together an isolation transformer can't hurt....and could prevent an accident.
That said, I wouldn't bother with a project like this, myself.
Thanks for all the replies. I have decided to part with the amp. I just do not feel too confident working with tubes and high voltage. I did put together few chipamps but messing around with 110V just scares me. Even with the isolation transformer I will still be working with 110V.
Here is a picture for those who asked: picture
Here is a picture for those who asked: picture
An externally hosted image should be here but it was not working when we last tested it.
That looks to be in great condition considering that it's likely made of near-cardboard. I saw a similar amp in a music store a few months ago. Fair-poor condition. I asked about it and the owner said it "they go for $2000 new.” I bit my tongue and played stupid by asking about the brand and how I didn't know that brand was available new. (It was some no-name brand.) He stumbled a little and said something about how “it’s boutique.” Real mumbo jumbo all around.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.