GCX + GCP + Marshall JCM2000 DSL100 channel switch issue

Q & A for building and interfacing your rack gear with Ground Control Pro and GCX-based systems.
Checco83
Posts: 7
Joined: Thu Feb 20, 2020 10:04 am

Re: GCX + GCP + Marshall JCM2000 DSL100 channel switch issue

Post by Checco83 »

I’m sorry, but I think I wrote 9VAC... confirm it’s 9VAC 1000mA. It’s the original power supply!

And I confirm I use phantom power to the Ground Control Pro!

Checco83
Posts: 7
Joined: Thu Feb 20, 2020 10:04 am

Re: GCX + GCP - switch issue on Loop#4

Post by Checco83 »

Hi JohnClark,
I rewrite to this "old" thread because the issue reported last year is not resolved.
Infact i connect a tuner to my Loop#4 and i use this Loop only a few times to tune and silence the guitar.

But now I HAVE TO solve this issue (because of a new pedal added! :lol: )

Summing up:
- The GCX is powered by 9VAC 1000mA power supply
- The GCP is phantom powered by the GCX
- I tried to change the istant number assigned to the Loop#3 and Loop#4 (to exclude GCP) but the problem on Loop#4 still remain
- I tried without any audio cable connected to the GCX
- I tested all the combination of the Loop and find another similar issue which I will explain later
- If you remember I sent you a photo of the internal GCX and you found no MOD to this used GCX (even if I think that if

This is the issue related to Loop#4 which arise in this occasion:
- Loop#3 and Loop#4 ON
-> Switch Loop#3 to OFF ==>> Loop#4 switch, internally to OFF (hear both clicks on Loop#3 and Loop#4 - no sound routed to pedal) but both LED in GCX and GCP remain ON on Loop#4 -> To turn ON Loop#4 again I have to switch to OFF the loop on GCP (LED now OFF) and then again to ON.

AND (and this is the new test done this days):
- Loop#3 and Loop#4 ON
-> Loop#2 ON
-> Switch Loop#2 to OFF, same issue ==>> Loop#4 switch, internally to OFF (hear both clicks on Loop#3 and Loop#4 - no sound routed to pedal) but both LED in GCX and GCP remain ON on Loop#4 -> To turn ON Loop#4 again I have to switch to OFF the loop on GCP (LED now OFF) and then again to ON.
In this second case, if Loop#3 isn't ON, Loop#2 and Loop#4 are working independent and normally.

Loop#4 (without Loop#3 ON) work as expected.
Loop#3 work as expected (except that if Loop#4 is active the issue occurs on Loop#4 as described above)
Loop#2 work as expected (except that if Loop#3 and Loop#4 is active the issue occurs on Loop#4 as described above)

How can I try to resolve??? Can I try to invert some relay to see if it's a relay problem?
Thank you very much for your help!!!

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