1999 MK IV B channel switching and LED issue

Dual/Triple Rectos, Maverick, Blue Angel, Nomad, Road King, F-Series, Lone Star & Stiletto

Moderators: Guitarzan, Grandor, ned, Platypus

Post Reply
Commander Coo1
Mark III
Posts: 234
Joined: Sun Dec 18, 2005 2:20 pm
Contact:

1999 MK IV B channel switching and LED issue

Post by Commander Coo1 » Tue Mar 06, 2018 1:59 pm

I have owned my 99 MKIV widebody combo for about 4 months, and I really enjoy playing it! for the past few months the loop LED has been fading in and out (no effect to the loop function). Then, Last night while I was playing the amp switched itself to R2. I figured my external switchin was the issue (not an FU3) so I removed the jacks, and used the rotary selector knob to change channels. OK, seems normal. I plug my switching jacks in 1 by 1 as i test functionality, and the problem is gone. I play for another 30 or so seconds and it goes back to R2. I unplug everything, switching jacks, FX loop, run guitar straight into amp, now the rotary switch on the back is not functioning either. slowly over the course of 25-30 seconds the amp changes from R2 to LD with a slow fade of the LEDs, then there is a strange woosh sound.

Did I have an LDR failure? any way to check? any other possible causes? other troubleshooting? Mesa says it will likely be $150-$250 to repair from my description...

Thanks,
James

Commander Coo1
Mark III
Posts: 234
Joined: Sun Dec 18, 2005 2:20 pm
Contact:

Re: 1999 MK IV B channel switching and LED issue

Post by Commander Coo1 » Wed Mar 07, 2018 3:38 pm

Looks like somehow the FX loop Autoassign was switched to R2. Not sure why this would cause switching issues but it did. I switched to the middle off possition and the problem went away. Does anyone else's behave like this?

Big Block
Mark II
Posts: 96
Joined: Mon Dec 10, 2012 3:44 pm
Location: Mile High City

Re: 1999 MK IV B channel switching and LED issue

Post by Big Block » Fri Apr 13, 2018 1:27 am

I had a IVB years ago that went haywire in the switching dept. Ended up being a short in the foot switch that fried an LDR. Was around $100 to fix back in 2008.

Post Reply