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I posted my original quandry on the vintage amp forum and thought I'd put it here also. I'm trying to restore to original, a Vox V125 combo fromthe early 80's. It has a speaker selection scheme that uses an external speaker jack and a switch to give the following combinations:
1)Either internal 8 ohm speakers or external 8 ohm cab connected to 8 ohm tap
2)internal 8 ohm + ext 8 ohm cab paralleled connected to 4 ohm tap
Here's a picture of the back of the jack/switch:
(red/pink=8 ohm tap, white=4 ohm tap, blue= ohm tap/earth, grey wires=internal speaker) The jack had been rewired as a line out and the speaker wires rerouted so switch no longer functions.
After pulling my hair out trying to figure it out, I think I have the wiring sussed. My quandry, the only way I can see to get the "OR" selection for the int/ext position is to rely on the connection of the tip bridge on the jack for continuity of the internal speakers. That way if an ext speaker plug is inserted, then the int speaker circuit is broken and the ext speaker is then connected to the 8 ohm tap. If the spring tension of the aux jack opens, then the internal speaker circuit is "open" and an output trans meltdown cuold insue.
Am I being overly cautious, or should I just wire it up directly to the speaker leads and tell the owner that option isn't available? This is kind of a rare beast and it would be cool if it was back to original and alive. But not at the expense of it possibly dying because of cheesy wiring.
Any thoughts?
Matt
1)Either internal 8 ohm speakers or external 8 ohm cab connected to 8 ohm tap
2)internal 8 ohm + ext 8 ohm cab paralleled connected to 4 ohm tap
Here's a picture of the back of the jack/switch:
(red/pink=8 ohm tap, white=4 ohm tap, blue= ohm tap/earth, grey wires=internal speaker) The jack had been rewired as a line out and the speaker wires rerouted so switch no longer functions.
After pulling my hair out trying to figure it out, I think I have the wiring sussed. My quandry, the only way I can see to get the "OR" selection for the int/ext position is to rely on the connection of the tip bridge on the jack for continuity of the internal speakers. That way if an ext speaker plug is inserted, then the int speaker circuit is broken and the ext speaker is then connected to the 8 ohm tap. If the spring tension of the aux jack opens, then the internal speaker circuit is "open" and an output trans meltdown cuold insue.
Am I being overly cautious, or should I just wire it up directly to the speaker leads and tell the owner that option isn't available? This is kind of a rare beast and it would be cool if it was back to original and alive. But not at the expense of it possibly dying because of cheesy wiring.
Any thoughts?
Matt