How do you get to the wiring?

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!

try checking out the wiring on your switch...if all is good try replacing the switch altogether...one of the other is bad...Good luck

I wouldn't offer him a tin can for it! I am a self-taught keyboardist, and I can tell you that something of that age and that price IS JUST NOT WORTH IT.

Is the battery installed in correct polarity? If so- try rotate it in position to rub through potential corrosion.

Since it has a remote battery, it would not hurt to look at the installation to make sure no wires are broken. Especially the ground wire to the pickup.

It might also be a good idea to apply some contact cleaner to the output plug since it is in the power circuit. Cycle the plug in and out a few times to clean the contacts. Also some contact cleaner to the preamp controls would be useful.

Be aware some lubricants may contain silicone and that can interfere with wood finishes or repairs to the finish in the future.

Open the unit and remove one wire from one of the woofer terminals and using an ohmmeter check the resistance between the terminals. It probably should be between 6 and 16 ohms... they don't give the specs on the speaker... if it is very high or infinite resistance, the voice coil is blown and you be re-coning or buying new speaker. These are close in speakers and intended for a small room for studio listening while mixing. If the speaker is OK, then the bass amp in the cabinet has a failure... pray, as that is cheaper to repair than a speaker.

There is something a bit more serious than the fuse. I would start by checking that the speaker itself is the correct type. This should be a 8 ohm speaker. Then I would play it and see if the output transformer is hot. This may be over driving the speaker. I would also look at the main power transformer. You might have one with the export transformer which can work with 110 or 220. I have no idea of your location so no idea which is your local level. Something is either over volt or over amps. Most of this amp runs at 15 volts and digital runs very cold compared to a tube amp.

I looked over the schematic and I just can't see anything else that would do that other than the things I have mentioned. A hot speaker is "very"unusual. If you can check the voltages with a meter this should be easy to point out the cause. It shouldn't take much for a amp tech to sort it out if you have to take it in. I wouldn't run it that much until fixed. When you see abnormal heat then something is being stressed. So you can cause more damage by using it. There may be a problem with the power transformer or votlage regulator stage but since the speaker is heating that could end up needing replacement if run too long.

Without having it in front of me I would sayy you may be looking at a new power transformer.or diodes and possibly caps. Any of those could cause the base issue. This is different enough with the hot speaker than I'm not that sure without seeing it.

Need more info: 1- does the volume control still change the level? 2-Does tone control still change the tone? 3- What happens when in the center position on pickup select switch? Put pickup switch in center position (both pickups active). Then take a coin and tap on the pickups. Does bridge pickup sound lower? Lastly remove rear electronics cover and inspect all wiring for something loose or disconnected.

If the bridge pickup has no continuity, replace the pickup.
I the pickup has continuity replace the switch.

check the "Gain" on the instrument you are plugging in ... if it is all the way down, that's the problem. If that's not it, check for a "Gain" control on the amp itself -- the is a volume control that takes care of the sound BEFORE it goes through the amp (pre-distortion etc.). Sometimes this is not with all of the other controls on the amp, so look carefully.
If it is not the gain on your instrument, and it is not the gain on the amp, then make sure you are not using too long of a wire to connect the two things. If you are using a 100ft cord to connect a guitar to an amp, there will be a lot of signal degradation in the wire, and it will be hard to get good volume from the amp since it is not getting enough signal to amplify.Try a shorter cord, and that might help ...
If all of these have failed, check the fuses on your amp. If there is a blown fuse anywhere, then your amp might not be getting the full power that it needs to produce the sound you are looking for (though a blown fuse usually cuts out ALL power through the amp, some models are built differently and this could cause your issue)
If none of these solutions work, try hooking the amp up to something else that you know works fine, to make sure it is the amp itself, not what you are hooking into it, that is not working right.
If all of this turns out to be an Epic Fail ... try speaking with customer service at the amp's manufacturer ... it might be a defect that they have seen before, and they may replace it, or at least give you a better solution that what I have done.

If you can't clean the pots or if you just want to try replacing them, try using
500k pots again, in case one or both of the pots is worn or dirty or
defective. If that doesn't work, and cleaning or replacing the
switches doesn't work, then the problem is probably elsewhere.
You could put a 500k resistor (with a sufficiently-high power rating of at least half the power rating (Watts) of the pot) in parallel with the pot, or, to cover all bases, put a 500k resistor from each of the two outer lugs of the pot to the middle lug. That should change it into the equivalent of a 250k pot. You could even just temporarily clip the resistors on, with alligator-clip leads, if you're very careful, just to test it.

Good luck,

The dude.