Hi Guys,
I've been loving my MP1 Classic, but yesterday out of the blue it developed a weird issue. It just started make a low-level crackly, farty sound whenever I play. I fiddled around with it and discovered it only does this on the tube voicings. The solid state presets all sound fine. So I thought bad tube, right? Well, I tried 4 different sets of 12AX7's of various brands and get the exact same results with all. So it doesn't appear to the tubes themselves.
I posted a YouTube video here so you can see/hear the issue:
https://youtu.be/P5i-Hhqy7W4
Any insight/guidance would be very much appreciated.
Thanks,
Brad
Could be R151, these go bad sometimes and then you can get this.(not always but it can). I'll take some pics tomorrow where to look for it.Do you have a multimeter?
Hi Brad,
No worries bro, you're in good hands. MJMP answered you in less than a half hour!! whow!
I love my Classic too, and will be watching this thread to see what happens.
Dante
Wow. You guys are awesome. Yes, I have a multimeter. Really appreciate the help.
Check this resistor with your multimeter, (do not turn the classic on!!) it should be 180k ohm.
Quote from: MarshallJMP on May 13, 2017, 08:24:14 AM
Check this resistor with your multimeter, (do not turn the classic on!!) it should be 180k ohm.
I'm getting 34.5 MΩ! That's 34million Ohms, right? I checked it multiple times to make sure I wasn't crazy. I'm guessing you've found the problem! :D
Yeah these go up in value so replace it and it should solve your problem. If not we'll look further !!
Wow, I hadn't seen a shot of the inside of a classic before, you can see the advance in PCB compared to MP-1/2
Yeah Richard,
It looks more like the PCB of the MP-2 than the MP-1. I remember posting that a long time ago when Jurrie was still with us.
It doesn't always looks like that, I attached a pic of my classic pcb.
Downside of the classic pcb's is that they are a b**ch to work on.
Quote from: MarshallJMP on May 16, 2017, 11:53:21 AM
Downside of the classic pcb's is that they are a b**ch to work on.
Yes they are! Which is why I still haven't gotten this done. I'm not quite savvy enough to do this one cleanly and I have a good friend who is an ace with the iron and working in tight spots on PCB's that I would rather have do it...but between his and my travel schedules we have yet to meet up and get this done. I will report back once we do. Thanks again!
Good thinking, if you're not 100% sure let someone else do it.
Well...I was finally home for a few days and was able to get the unit over to my buddy's place and work on it. We put in a new 180K resistor in R151 and...Boom! It works perfectly!
Thanks so much for the help. Truly awesome.
:whoohoo!: great news :thumb-up:
Sweet! :thumb-up:
MJMP = Epic Winner! :thumb-up:
Well that's great news !!! :thumb-up: