I have a marshall footswitch with two buttons , being channel and reverb, i can get it to switch from nothing at all to switching on at a normal volume but i cant figure out how to get it to switch from a set normal volume to a different one, as i dont have the instructions its tricky figuring out how to :/ i couldnt find the name of the product because i dont know the name sorry :( so i put a random name in

I once used uART & some latches to decode & hold the difference between "odd & even" midi program changes. Then used the output to switch a relay in a twin necked guitar to change between necks as it were in response to a midi pedal. Perhaps you could do something similar? Else get a Studiomaster MA-36 midi analyser & hack into it to use one piece of midi data (from across an LED?) to switch channels on your amp? Good Luck!

Need more info. What kind of foot switch and what are you hooking it up to. For guitar they are used for switching distortion to clean on 1 switch, one for reverb, one for chorus, and possibly 1 for bypass. All depending on the amp you use, and what effect the amp has built in it. Some amps only have clean and destortion which make the other channels on the footswitch useless. Hope this helps.

Nothing wrong with the amp. Google it- these amps have extremely weak reverb. All of them are the same. It's the one weak point about these amps. And I love mine. I mic it when we gig. Sounds awesome both clean and driven. But you'll have to get a separate reverb pedal if you want "girl crush" or "pipeline" reverb. Don't listen to the above posters. It's the way these amps are.

The schematic shows it as a standard 1/4 inch stereo plug. Wire the ground common to both switches (Channel and DFX), the ring to one switch and the tip to the other...I.E. ground (sleeve) to ring for one switch and ground to tip for the other. You'll have to experiment with which switch operates what function and label them accordingly.

Sounds like either your "front-panel" switches are not set for channel switching or the footswitch's mechanical "Channel" switch is defective. According to the OM the "Channel Select Switch" on the front becomes inactive with the footswitch plugged in.

If disconnecting the footswitch causes this front-panel switch to operate properly then it has to be your mechanical switch in the footswitch. Repair of these footswitches are pretty simple provided you find a replacement and have soldering abilities.

Does your M foot switch work on the Fender? If you know how to use a multimeter you could check continuity by putting meter leads on plug of M foot switch(1 on tip, 1 on sleeve ) You should see a change in the multi meter when you depress switch. If so switch is good. Another easy test is with cap off a spare 1/4 plug -plug it in to foot switch jack.put a alligator or some such metal clip or wire and join(called short or shorting) the two inputs . If connecting and unconnecting results in switching then the foot switch is suspect. One fairly common thing is that foot switch and input jack are often sautered straight to a circuit board to save $ on production cost. Used to be all point to point where a wire was attached to 1/4" input and then wire went to circuit board or tubes. The wire has give, but not so with direct wiring to board. So the nut holding the 1/4" amp input gets loose(doesn't have to be loose for the following to happen) and a pull on the chord causes a break in the soldier and thus a break in the sound chain. Sometimes it will work intermittingly by putting a little pressure left, right, up or down on the plugged in plug. If so, it's the input jacks connection to the amp. If not it still could be that because putting pressure on plug may not be sufficient to affect a temporary reconnection. Since switch(the new one you made)works on Fender, but not Marshall I suspect the jack or foot switch circuitry past the input jack. If using some of the above the above tests leads you that direction,remove housing(unplug a/c power 1st ) inspect jack,wiggle it slightly see or feel a break then resodier from back side. You should be able to use the soldier already present without adding extra.

The P803 is designed to work with the "Valvestate" and Tube amps. I don't think it is compatible with the Haze40 since they have an optional 4 button footswitch so the optional one would necessitate different interface than the P803.

Insufficent information !!! Are you controlling this by the footswitch or the onboard switch? If the onboard switch and you HAVE at some point used the footswitch, likely the contact on the footswitch jack has failed that transfers control to the internal switch. If you haven't tried the footswitch see if that has control. I can send you the link to the schematics if you know how to read them. Here they are:

http://elektrotanya.com/marshall_mg250dfx.pdf/download.html

Scroll down to the little link that says "Get Manual" and click on it to download.

Check Ebay

have you tried the footswitch to change channels. also. my amp has to be in channel 2 position (with the button on the head) before i can use the footswitch. sometimes the input/footswitch jack wears out and you need to bend the internal tip/ring tabs of the jack to make better contact. also like on my fender amp, i had just a standard mono instrument cable going to my footswitch and it was acting wierd cause it needed a stereo instrument cable. one last thing on the grounding resistors on the pcb, they get hot and break the solder welds which messes with all sorts of stuff in amps. usually look like sugar cubes , cement resistor. 5watt usually under 1k ohm. check for bad solder welds on the pcb where the big resistors are and the switches/buttons and at the footswitch. there may be a bad ic or transistor for the channel swithing