Fitting a footswitch to a Marshall MG15r

Lestratcaster

I've got the above amp, which I use for teaching and I like it. Only problem is I can't footswitch between clean and dirty channels as it doesn't have one built into it.

Is there a way to tinker with the circuitry and fit one in? How easy is it to do?

ICBM

Which version is it - the earlier one with a square channel switch button or the later one with a round button with an LED in it?

Lestratcaster

The later one with a round channel button switch the the LED.

ICBM

I'll see if I can find a schematic. It may be promising though, because I think that is just a momentary switch which operates some control circuitry, so in theory if you simply connect a jack in parallel with the switch, then a momentary footswitch should do exactly the same job.

Does the switch click to different 'in' and 'out' positions, or return to the same position each time? I can't remember.

Lestratcaster

Hmm so its a case of opening the back, and swapping a part? And adding a jack?

The switch doesn't click in or anything it just changes colour.

ICBM

Lestratcaster said:

Hmm so its a case of opening the back, and swapping a part? And adding a jack?

The switch doesn't click in or anything it just changes colour.

I've got the schematic now - yes, it should be as simple as fitting a jack in the back panel and connecting it to the two terminals of the push-switch so it duplicates the function. There may be some complication in getting at the terminals, or identifying which is the ground side, but that may be all there is to it. The footswitch jack must be insulated from the chassis, but if you're drilling through the back board it will be anyway.

Can you take a pic of the inside of the chassis, looking forwards towards the front panel?

Lestratcaster

Hmm...may be able to get away with a DIY jobby but don't want to mess it up!

The amp is downstairs in storage at the moment but will get a pic tomorrow when I can take the back panel off unless there's some google image clips lurking about.

ICBM

Lestratcaster said:

The amp is downstairs in storage at the moment but will get a pic tomorrow when I can take the back panel off unless there's some google image clips lurking about.

I've had a look already and can't find any of it - just the older version.

Lestratcaster

Ok no worries, will get a photo tomorrow and whack it up on here.

Where would I potentially get such jacks and switches from?

professorben

Lestratcaster said:

Ok no worries, will get a photo tomorrow and whack it up on here.

Where would I potentially get such jacks and switches from?

Maplins. 

ICBM

This jack would be ideal -

https://m.ebay.co.uk/itm/CLIFF-ELECTRONIC-COMPONENTS-S2SNS-SOCKET-1-4-JACK-UNSWITCHED-2POLE-/171118832795?_mwBanner=1

For a footswitch, anything with a momentary switch which is normally open should work - some have polarity switches, eg the Boss FS-5U. If possible try to get one where the casing is not grounded (the Boss is not, I'm pretty sure), since it will be carrying 7.5V DC from the amp, and you don't want it to short against anything - not dangerous to you, but possibly to the amp.

Lestratcaster

For the life of me I can't seem to get the panel off the back of the amp! Have unscrewed all 9 of the screws and tried a flathead screwdriver to try and hinge it but no use. Is it meant to be designed so it can't be removed or something?

zepp76

I'd be using this problem as an excuse to buy a new amp, but then I always did find it hard not to give in to GAS!

Lestratcaster

Haha I played through a Marshall dsl5c yesterday and it's got foot switchable channels, I did like it!

ICBM

Lestratcaster said:

For the life of me I can't seem to get the panel off the back of the amp! Have unscrewed all 9 of the screws and tried a flathead screwdriver to try and hinge it but no use. Is it meant to be designed so it can't be removed or something?

It's very likely stuck to the vinyl - not intentionally, it just happens because the vinyl is soft and slightly sticky, so the panel sticks to it under the screw pressure. They can be a bugger to get off sometimes - try not to lever it out, you'll probably chew it up. You may have to find a much larger self-tapping screw which will thread into the panel and not right through into the amp, and use that as a puller.

Lestratcaster

Yes I had a few digs with the flathead and it started ripping the wood so I stopped before it became any worse. I've had a look around for other sized flatheads but can't find one to fit in the panel