On my Crate CPM8FX, why does channel 1 short out?

https://www.scribd.com/doc/55465995/Crate-PA-6-Manual
https://www.scribd.com/doc/55465995/Crate-PA-6-Manual

Try with a on/off footswitch Wrong cable, or bad PCB connection switch on main tone board.

You trying to fix it or sell it ?

They look to be 1/4" stereo male to male jacks (known also as TRS). I don't know where you are but they are easily available.

You need a pair of them at the length you need.

e.g. SHORT 1m 6 35mm Stereo TRS Jack Plug to Guitar 1 4 Jack Male Musical...

Hi, you hadnt mentioned how long you've had the amp, or how new it is, so I'm going to assume it's new to you. The Crate VTX200 has 3 channels, each with its own volume level. Let's check the simple things first:
1. Check to make sure you're adjusting the same volume knob volume knob to the same channel. The active channel will be lit with a green light.
2. Check the cables from the "Speaker Out" jacks on the amp (if you are using them). Are they plugged in all the way, or are they damaged?
3. Are you playing through a preset that you may have accidentally made "low", and may not be aware of or are stuck in it?
If none of these answers helps, there might be a problem with the input buffer in the circuit or possibly within the damping circuit of the speakers. I'd advise having the amp serviced to confirm an internal electrical problem also. If you don't have a manual for the amp, one can be found here:
http://www.manualguru.com/crate-amplifiers/vtx200/users-manual

because something in it is shorted..shop time.

in some models there are relays that are slower to respond than others. Contact Crate to see if there is a fix for your model.
http://www.crateamps.com/support/index.php

I also have this issue. Same crate combo amp. There is a loud buzz emitted only when there is a cable plugged in. Cables and instruments checked good, only possible issue is inside the input of the amp. Popped it open, solders and connections were intact and appeared solid. Anyone have a guess as to why this is happening?

sounds to me like your din plug on your controller is messed up ? hope this helps !

I can understand your confusion... and a lot depends how you are going to use this. There are some caveats regarding the connections,
If you use the 1/4 outputs on the GSP, there is a speaker modeling like function that is NOT available, that IS available IF you use the XLR outputs.
The STP is an "Insert Snake" which is not really what you want as it is intended to send and receive (audio going both directions in the cable.
If you want that speaker function, then you should get two XLR to 1/4 TRS cables and go from the XLR's on the GSP to the Left and Right inputs on the back of the Crate. Your audio or guitar then is connected to the GSP guitar input.
If you connect the guitar to the crate and then use the STP, Plug the TRS single connector into the Left/Mono/send/rtn on the Crate. The Send cable of the Y should go to the Send jack on the back of the GSP and the return should go to the left return jack of the GSP. This connection I would NOT recommend as it will be noisier and you will lose the stereo effect capabiltiy since the effect is inserted as a mono.

I believe you would be happier with using the XLR's to carry left and right to the Crate and run your inout to the GSP. In short, you have the wrong cable to do the best job.