ch switch

[nickb]

Relay http://www2.mouser.com/ProductDetail...2b5gblmWyl0%3d

The heater winding refers to the power transformer where that feeds the heaters of the valves. It is rectified to provide the DC supply. The diodes can be IN4001-7 or even a single bridge rectifier. You might need to add a resistor in series with the replay coil. maybe 47 ohm or so to get 5V or so across the relay when operating. The 1000uF cap will need to be at least 10V. U26 is the front panel switch.

[Valvehead]

What Juan described is pretty much exactly how I did it. I used a plastic jack for the footswitch connector to isolate it from the chassis. I still have the schematic (below). The two coils marked LU20 are the two relays, you will need only one. One set of contacts is used for the channel switch, the other for the LEDS. There is no need for bleed resistors Enzo mentioned as there is no DC on the contacts - proven and tested in real life. I did get some noise on the rectifier supply and the purpose of the 100nF ceramic capacitor is to remove that.

[ATTACH=CONFIG]44467[/ATTACH]

ok looking at that scem...tell me if im understanding this... the left side just shows basically 2 wires that can come off V1 heaters...then gets rectified by D1-4 . Jack should be a plastic stereo model ?

L5 / L6 is just the 6.3v ac ?

[nickb]

ok looking at that scem...tell me if im understanding this... the left side just shows basically 2 wires that can come off V1 heaters...then gets rectified by D1-4 . Jack should be a plastic stereo model ?

L5 / L6 is just the 6.3v ac ?

Correct, except the socket is a plastic mono type with a switch contact that is closed when no jack is inserted.

[Valvehead]

ok -thanks!
so would the 47 ohm go right after D4 to get close to 5v?

and i wouldnt need U26 switch if using a fsw?

what would i leave out if not using the LED's ?

[nickb]

ok -thanks!
so would the 47 ohm go right after D4 to get close to 5v?

and i wouldnt need U26 switch if using a fsw?

what would i leave out if not using the LED's ?

The 47 ohm ( value is a guess) goes in series with the relay coil, not D4.

You can replace U26 with a wire link if you are sure that a footswitch is all you need.

If you don't want the LEDS, you leave out the two LEDs ( ) the 330 ohm resistor and you won't need to wire up the second pair of relay contacts.

[Zouto]

Here you can find a similar solution
http://music-electronics-forum.com/a...footswitch.jpg
Best greetings and good luck
Zouto

[olddawg]

Maybe I'm missing the point of this whole thread... but if you want to switch between 2 front panel input jacks, why not just have an A/B switch onthe floor? One cable in. Two cables out to the respective inputs. Are the grounds isolated? Even if they are it's not a big deal to switch the ground and the signal.

[Enzo]

Look at the schematic. This is the amp circuit wher the high gain jack feeds into an extra gain stage. Plugging into the low gain jack disconnects that stage and the signal enters at stage 2. SO by plugging an AB into both input jacks means the high gain jack will no longer pass signal.

[nickb]

Maybe I'm missing the point of this whole thread... but if you want to switch between 2 front panel input jacks, why not just have an A/B switch onthe floor? One cable in. Two cables out to the respective inputs. Are the grounds isolated? Even if they are it's not a big deal to switch the ground and the signal.

Normally that would work but in this case inserting the low jack disconnects the high jack.

[olddawg]

Normally that would work but in this case inserting the low jack disconnects the high jack.

Then the simplest thing to do might be to defeat that function and use an A/B box? Might be an easier and less invasive mod?

[Enzo]

Look at the schematic, it isn't quite that simple.

[Valvehead]

Here you can find a similar solution
http://music-electronics-forum.com/a...footswitch.jpg
Best greetings and good luck
Zouto

ok, so where it says where the relay pins go to a turret......is this for a 2203/ 2204/ marshall? are they talking about the stock parts on the Marshall board?? is there any more info on this one?

[Valvehead]

The 47 ohm ( value is a guess) goes in series with the relay coil, not D4.

You can replace U26 with a wire link if you are sure that a footswitch is all you need.

If you don't want the LEDS, you leave out the two LEDs ( ) the 330 ohm resistor and you won't need to wire up the second pair of relay contacts.

next question---- where exactly is this circuit connected in a 2203/2204 ?? and where are the connections on this circuit that will go to the amp?? The Low jack in the amp can go away if needed and im adding a second volume

[Valvehead]

Can anyone tell me where relay pins 3 / 7 / 8 would go in a 2203 Marshall? Or ...where is my signal coming in / out of that relay ?


http://music-electronics-forum.com/a...footswitch.jpg

[Gnobuddy]

The original one has no switch, as you say, you must manually unplug and re plug your cable

Adding a relay is the engineer's approach to the problem. It's a bit complicated, but once it's done, it's elegant and self-contained in the amp.

Then there is the "I just wanna play through the darn thing!" guitarist's approach. That is to use an A/B box. Guitar goes to the A/B box, cable from "A" output to clean channel, cable from "B" output to overdrive channel, and you're done. Step on the footswitch to switch channels.

Using an A/B box is not as elegant a solution, because you now have to carry around the A/B box and two extra guitar cables. But it is quick, simple, and effective.

If you feel like it, you can build your own A/B box, too. Get a Hammond die-cast aluminum box, three mono 1/4" jacks, a footswitch, and a handful of other parts (LEDs to indicate which output is in use, power jack), and it's an easy build.

-Gnobuddy