I'm restoring this amp. It lacks a power transformer so I'm rewiring it with an isolation transformer. (A 3 prong cord was already installed)
I noticed that the volume control puts the excess signal to the mains?!?!? Should this go to ground instead?
Any other safety things that should be done to this amp?
I'm figuring the mains side of the isolation transformer is the side that should be switched and fused.
I noticed that the volume control puts the excess signal to the mains?!?!? Should this go to ground instead?
Any other safety things that should be done to this amp?
I'm figuring the mains side of the isolation transformer is the side that should be switched and fused.
Attachments
That circuit is insane. The node A is the audio common. Yes, fuse and switch on the primary.
Your isolation transformer secondary should feed the half wave rectifier diode and 50uF capacitor.
Reroute the input stage common to node A.
Your isolation transformer secondary should feed the half wave rectifier diode and 50uF capacitor.
Reroute the input stage common to node A.
Should the 150 ohm resistor at the AC in be there? Should it maybe be an inrush thermistor instead?
I should know this, but where/what is the input stage common?
I should know this, but where/what is the input stage common?
The resistor is for the heater wiring, to drop some voltage.
Actually there are more changes required, stay tuned.
Actually there are more changes required, stay tuned.
Thanks for your help, no hurry.
There's a couple differences between this schematic and the amp in front of me. The 20uF cap isn't there, the can cap is just two 50uF caps. And there isn't a lamp.
There's a couple differences between this schematic and the amp in front of me. The 20uF cap isn't there, the can cap is just two 50uF caps. And there isn't a lamp.
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Whatever you do -
DO NOT use this amp until it has been rebuilt with full AC line isolation,
and until it has been fully vetted here. It is a death trap.
DO NOT use this amp until it has been rebuilt with full AC line isolation,
and until it has been fully vetted here. It is a death trap.
That guitar amplifier is a perfect example of the saying "a little knowledge can be a dangerous thing".
In this case, fatal.
In this case, fatal.
We don't want such dangerous circuits posted here. Someone might actually build it.
Can you draw it with a transformer and repost?
Can you draw it with a transformer and repost?
Ah, thought something was just glitching.
I've edited in a transformer, added an X where the volume pot connects to AC, and added a warning.
I've edited in a transformer, added an X where the volume pot connects to AC, and added a warning.
Use a fully isolated 110 to 110 transformer. The device will operate safely. You can use fuses at the input and output of the transformer.
I noticed that the volume control puts the excess signal to the mains?!?!? Should this go to ground instead?
Any other safety things that should be done to this amp?
Is your question about volume? I didn't understand what it means to give a signal to the power? One pin from the volume must connect to ground...
Any other safety things that should be done to this amp?
Is your question about volume? I didn't understand what it means to give a signal to the power? One pin from the volume must connect to ground...
Instead of one pin from volume going to ground it goes to the AC mains!
rayma said to "Reroute the input stage common to node A." but I'm not sure what that looks like.
rayma said to "Reroute the input stage common to node A." but I'm not sure what that looks like.
The second method is better because it takes the power consumed by the filament from the isolation transformer. Connecting the filaments to the city electricity... does not create a hot chassis and does not a shock to player.
Without an isolation transformer...the amplifier ground is connected to a city power connection. And so you think the volume is connected to the power. Connect the transformer and do not touch the circuit combination.
The reason. of rayma.. Advice...... is electric shock if someone touches the metal part of the volume . So... said, disconnect the volume from the ground line ... or live electricity..This is not a signal to power.... 😒
The reason. of rayma.. Advice...... is electric shock if someone touches the metal part of the volume . So... said, disconnect the volume from the ground line ... or live electricity..This is not a signal to power.... 😒
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