Here are the details of the mod in follow up to my post on the "What has happened to the VG Strats" thread. (As a Newbie I didn’t see this thread at the time). Grateful thanks to Thaus for offering to help me upload it
In the absence of detailed schematics from either Fender or Roland, I modified my VG Strat to overcome the problem of battery drain by installing a switch on the mode control so that it automatically turns off the battery power when "N" [normal strat] is selected.
An advantage of this mod is that it doesn’t change the guitar cosmetically. The switch operates with the mode control and the blue LED comes on only when the VG modes S, T, H or A are selected.
The work involves soldering and it’s quite fiddly with a tiny micro-switch to be mounted beneath the Mode control. But all is hidden under the scratch-plate and, once finished, it works like a charm!
There's a slight pause in output when changing from "N” to the modelled sounds but I've not found it a problem as I don’t need to change settings during a song and there's no pause when changing back to "N".
Apart from soldering iron, solder,and a short piece of twin light gauge wire,, the main item is a micro-switch and a very small nut and bolt (or glue – see below) to attach it. Some shrink wrap insulation is also best if you want to make a tidy job of the soldered joints – but insulation tape would do just as well.
Beneath the scratch-plate, the Mode control knob operates a rotary switch that has a flat-sided cam holding a spring-loaded ball bearing that produces the ‘clicks’ as the control is turned. The cam is used to press against the micro-switch to disconnect the battery power.
The micro-switch used is the Cherry DH3CB1LA - Google it to find a supplier in your area. I got mine from Camis Electronics Ltd in the UK. It’s only 8mm wide and 2.7mm thick and when pushed, it switches off and when released, it switches on.
Step By Step
1. Start by de-stringing and removing the scratch-plate.
2. Remove the mode switch ("M") from the scratch-plate by first gently removing the three wire clusters/connectors - see pic 1. You don’t have to worry which is which ‘cos each one is a different size and can only fit in its matching socket.
3. Prise off the control knob and loosen the mode switch securing nut to completely remove the component from the guitar – see pic 2.
4. Line up the actuating blade of the micro-switch so that it is pressed shut when the flat cam under the control is fully counter-clockwise (ie when the control knob corresponds to the “N” position) – see pic 3. It must be secured in place in just the right position. . I used a small nut and bolt (see pic 3) but perhaps epoxy glue might be just as effective.
5. The micro-switch needs to be secured in this position and it’s important to check when the control knob is turned clockwise to the first “S” position, that the blade of the switch is released (the cam moves away from it) so that it switches on and remains on while the switch travels clockwise to the other modes T, H &A.
6. To fit the small nut and bolt you will have to drill a small hole in the top frame of the rotary mode switch – see pic 4. This was the fiddly bit and after some trial & error; you can see that I ended up drilling and extending more than one hole before I got the micro-switch to operate just right. To keep the micro-switch positioned parallel to the cam, I used a small washer between it and the mode switch frame. Also, you can see (pic 4) that there is only just enough room for the micro-switch, the packing washer and a single nut so, after tightening it, I applied a drop of (Uhu) glue to the nut, switch and the screw (bolt) ends to stop them from working loose over time. If you have one, it’s helpful during this stage to use a multimeter to check the micro-switch works just right – otherwise wait ‘til the hook up stage (9. below) before finally securing with nut, bolt & glue.
7. Next, remove the cover of the VG circuit on the back of the guitar – see pic 5. and make a suitable break (cut) in the white wire of the black & white pair that is connected between the VG unit and the guitar output jack socket. On Pic 5 it is next to another black &white pair connected to a blue plug & socket on the VG unit. The new micro-switch is to be wired in series with the switch on the jack socket that switches on when the lead is plugged in.
8. Cut into the white lead and solder your short (new) piece of twin wire to the two cut ends. Make sure you cover up/insulate the bare soldered joints before threading the other end of the twin wire through into the control cavity at the front of the guitar.
9. Finally, solder the other ends of the twin wire to the two pins on the micro-switch that, by now, should be attached to the Mode rotary switch. On the Cherry DH3CB1LA micro-switch, the two wires connect to the two outside pins (doesn’t matter which way round); the middle pin is left unconnected. Insulate the soldered joints as before. Test again that the switch works as intended before re-fastening the mode switch to the scratch-plate and putting everything back together again. Pic 6 shows the completed switch installed on the guitar but as only 5 attachments allowed, I'll send it later.