5e3 Internal jumpering on an on/off switch

[martinman]

Hi,

I'm thinking of removing 3 of the inputs to make room for some modifications (i.e. switches to engage the mods). I'd still like the ability to jumper the channels, so I was thinking of doing this internally.

Looking at the circuit, it seems that I can accomplish this with a 68k resistor to bridge pin2 and pin7 of v1. This of course would make it permanently engaged. Can I wire this 'bridge' to an on/off switch so that I can switch it out when desired?

Full disclosure: This will be my first mod - any help is appreciated. Yes, I've build a few amps. Yes, I know the safety aspects of this.

[martinman]

Did some searching, and found this thread:
http://music-electronics-forum.com/t20423/

Seems like resistors are not needed? I'm not exactly sure why they are needed in the first place?!

[martinman]

Ok, so 80 views, and no response. I'll just keep posting with more info until I do something so stupid that you *must* point out my ignorance ala true internet fashion .

So, I
1) removed the inputs for both normal channels
2) capped the leads going to the input jacks
3) bridged pin 2 + 7 on V1.

Apparently (well.. quite apparent really) this wasn't the correct thing to do as I now have a significant hum. I suspect that I messed up the grounding scheme. Or, because the leads to the input jack are essentially 'flying' that this wasn't correct.

I suspect that I should have also disconnected / decoupled pin2 from the lead going up to the input jacks. Doing this tonight. This seems to be how it's done on the 5f1 with a set of 2 inputs (amazing how similar these things are really)...

Anyway, back to the drawing board.

Something that also popped into my head -- I wonder if I could put a linear pot inline with the v1 2 - 7 bridge and dial in a much 'blend' I want between the two channels. This would replace the on/off switch essentially.

More this weekend.

[martinman]

Put everything back to stock this weekend. No hum. Must be something with the inputs -- thinking 1M 'reference' to ground (but not actually sure what that means).

Rather than removing both at the same time, I took out 1 input - normal #2 by desoldering 68k from board thus removing it from the circuit (also disconnected the input from normal #1 and removed the entire thing from the chassis. (anything sort of this would cause quite a bit of hum). My current thinking -- perhaps I hardware the inputs pre - 68k resistor. You know, remove the jack, but make sure the leads to the board are connected. Anyway, going to try this next.