# Weird Twin Problem



## ampaholic (Sep 19, 2006)

I'm taking a peek at a friend's silverface MV Twin that has a strange problem. On both the Normal and Vibrato channel the input #1 works but input #2 on both channels does not.
Am I missing something here? The only thing separating input 1 and 2 on each channel is a 68K resistor. I've checked grounds and everything seems ok. Since input 2 is dead on both channels I've searched for something common to them both. In looking at the schematic the only component that even remotely connects the two channels prior to the phase inverter is the Pull Boost switch.
Any ideas?


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## WCGill (Mar 27, 2009)

Nothing connects the input 1 or 2 jacks from one channel to the other so it can't be one problem causing this. By some fluke it could be the same problem on each jack though. Weird indeed.


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## ampaholic (Sep 19, 2006)

Here's what I've found. When I first looked at this I thought it was factory wiring but the more I looked at it the more it didn't make sense. On the #2 input of both channels there is a wire soldered across the 68K resistor that is connected to the 1 Meg resistor on input #1.
The result is that even with a cable plugged into input #2 the signal is shorted to ground through input 1.
I'm assuming this isn't factory wiring but I'm not sure why someone would do it. It takes the 68K resistor out of the circuit in input 1 which maybe livens things up a bit.
Anyway, I unsoldered one end and bingo, input 2 works. Here's a photo of the wire that I unsoldered.








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