Johnson JA-40WT Footswitch

[SmogFighter]

Hi All,

My Johnson amp is having a problem. When I use a footswitch, the amp
doesn't really switch between channels. If I have it on "clean" and I hit
the switch, the "overdrive" light (LED) comes on dim and no overdrive.
Same goes for when I have it in "overdrive".

I have searched for a schematic, including contacting Johnson, to no avail.
I did find a manufacturer (through the help of this forum (Thanks Steve!))
that has a "re-badged" version of my amp. they were kind enough to list a
schematic http://www.axlguitars.com/schematics/AA-AK-40.pdf.

After re-looking at the that schematic, I think i need to find a double
footswitch (2 switches, 1 stereo plug).

what do you guys think?

Thanks for your help,
Raul

[oc disorder]

Hi Smogfighter
Yes you are right .The footswitch has a tip,ring and sleeve plug (6.5 stereo)and 2 switches.
But as the tip activates the channel switching it still should work with a mono plug (tip and sleeve).
On first look it seems like there are a lot of connectors and switches in
the pathway of the switching circuit.
Any "bad connections" there ie grit in switch poor contact..cracked solder joins on connectors including the footswitch socket itself could cause problems.
There are 4 relays in the circuit they are like remote controled switches.
On the schematic in the footswitch area they are shown as a spiral with a parallel line next to it.RL1 RL 2..RL4 .
When those relay coils (spirals) are energised (f/s or front panel switch allows current to flow through them) their switch contacts change over .
Their corresponding contacts are shown as a changeover switch in a little box
in the signal path labeled RL1-A RL2-A etc.
Also an electronic switch is used in two places that I can see TR1 a JFet
is used to short out the gain control or not and another for turning off the reverb TR5 which shorts out the reverb volume or not which is controlled by the footswitch connected to the ring.
So first step make yourself or buy a duel f/s with a TRS plug and either seek help back here which will require a meter and some soldering skills or take the amp and the schematic to a suitable tech.
EDIT: I find the brand name footswitches like Carling (not the UK lager the ones Fender used to use)are much more robust than the cheaper modern ones.
I've replaced more modern ones (in effects and Marshall) than I have the older Fender ones like in 60's Twins etc.

[SmogFighter]

I tried a Crate footswitch...

I have a Crate GLX212 that has a 3 switch footswitch. One is used for effects
on/off. Another is used switch from "Clean" to the distortion channels.The 3rd,
is used to select between the 2 distortion channels.

Initially I used the single switch (effects on off) which has a stereo plug to try
the channel switching on the Johnson. Then, as I was making this post, I
realized that I should be using a 2 switch Footswitch because of the addition of
the reverb on/off.

So, when I got home last night, I plugged in the 2 switch side. the reverb
on/off works great. But, I am still not getting the clean/overdrive switching
like it should.

I did notice however, that looking at the Axl Akita version of my amp, there
is a pushbutton clean/overdrive switch. mine has a simple toggle type switch.
Which leads me to look at the amp mounted clean/overdrive switch to find the cause.

Thanks,
Raul

[oc disorder]

I'm not familiar with the Crate GLX212 3 button footswitch but it is possible
that it has some active components in it to enable 3 way switching on a 3 conductor connection thus not suitable for the Johnson.
All your Johnson requires is one switch that switches to ground using the tip and sleeve for the lead and another switch that switches to ground using the ring and sleeve for the reverb.
Does it switch ok from the front panel between clean and overdrive using the toggle switch ?

[SmogFighter]

I'm sorry, the Crate has 2 "ring-tip-sleeve" cords coming from it. 1 is effects
on/off, the other is for overdrive on/off and OD-a/OD-b.

the "OD on/off" switches sleeve to ring

the "OD a/b" switches sleeve to tip
i will verify this when I get home today

[SmogFighter]

Verified footswitch operation last night.

I'm sorry, the Crate has 2 "ring-tip-sleeve" cords coming from it. 1 is effects
on/off, the other is for overdrive on/off and OD-a/OD-b.

the "OD on/off" switches sleeve to ring

the "OD a/b" switches sleeve to tip
i will verify this when I get home today

Just as I had thought, with no cross talk between them.

And the effects on/off switches only the tip of the other cord.

Next step is to see how the toggle switch mounted in the cab is wired....