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Temp "Time Format" issue Fix in Discussions

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Author Topic: Problem with Tube Voicings on Classic  (Read 1972 times)

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BradS71

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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
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MarshallJMP

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Re: Problem with Tube Voicings on Classic
« Reply #1 on: Time Format »

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?
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Dante

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Re: Problem with Tube Voicings on Classic
« Reply #2 on: Time Format »

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
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ADA Gear: MP-1 Classic | MP-2 | Viper Combo | MicroTube 200 | MicroFet | MXC w/Quad Switch

BradS71

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Re: Problem with Tube Voicings on Classic
« Reply #3 on: Time Format »

Wow. You guys are awesome. Yes, I have a multimeter. Really appreciate the help.
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MarshallJMP

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Re: Problem with Tube Voicings on Classic
« Reply #4 on: Time Format »

Check this resistor with your multimeter, (do not turn the classic on!!) it should be 180k ohm.
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BradS71

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Re: Problem with Tube Voicings on Classic
« Reply #5 on: Time Format »

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
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MarshallJMP

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Re: Problem with Tube Voicings on Classic
« Reply #6 on: Time Format »

Yeah these go up in value so replace it and it should solve your problem. If not we'll look further !!
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rnolan

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Re: Problem with Tube Voicings on Classic
« Reply #7 on: Time Format »

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
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Studio Rig: MP2/MB1 > Eurorack UB2442FX-Pro > TC M-One XL > Behringer Truths (with Truth Sub) / QUAD ESL 63s
Live Rig: MP2/MB1 > Alesis Quadverb > Alesis Midiverb 4 > Yamaha AM802 > B200s/Carvin TS100/DCM200L > ADA Split Stacks/Mesa P112s

Harley Hexxe

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Re: Problem with Tube Voicings on Classic
« Reply #8 on: Time Format »

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.
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MarshallJMP

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Re: Problem with Tube Voicings on Classic
« Reply #9 on: Time Format »

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.
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BradS71

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Re: Problem with Tube Voicings on Classic
« Reply #10 on: Time Format »

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!
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MarshallJMP

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Re: Problem with Tube Voicings on Classic
« Reply #11 on: Time Format »

Good thinking, if you're not 100% sure let someone else do it.
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BradS71

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Re: Problem with Tube Voicings on Classic
« Reply #12 on: Time Format »

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.
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rnolan

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Re: Problem with Tube Voicings on Classic
« Reply #13 on: Time Format »

 :whoohoo!: great news  :thumb-up:
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Studio Rig: MP2/MB1 > Eurorack UB2442FX-Pro > TC M-One XL > Behringer Truths (with Truth Sub) / QUAD ESL 63s
Live Rig: MP2/MB1 > Alesis Quadverb > Alesis Midiverb 4 > Yamaha AM802 > B200s/Carvin TS100/DCM200L > ADA Split Stacks/Mesa P112s

Dante

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Re: Problem with Tube Voicings on Classic
« Reply #14 on: Time Format »

Sweet!  :thumb-up:
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ADA Gear: MP-1 Classic | MP-2 | Viper Combo | MicroTube 200 | MicroFet | MXC w/Quad Switch
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