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Temp "Time Format" issue Fix in Discussions

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Author Topic: MB-1 no output  (Read 388 times)

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peoriashows

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MB-1 no output
« on: Time Format »

I mentioned this to MarshallJMP over an email, but thought I'd bring it here in case anyone else needed help troubleshooting. One of my MB-1 bass preamps is not outputting sound. Input jack seems okay. When I hook a signal generator up to it, I can see a signal out on the Direct out pins, but nothing on the 1/4" output jacks (full, high, nor low) I'm wondering if the problem is starting back at the HP input on sheet 3 of the schematic. What is the K402? Is that the connector for the volume pot? I tested the pot and get continuity. Any suggestions or where to go from there? Thanks.

« Last Edit: Time Format by peoriashows »
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peoriashows

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Re: MB-1 no output
« Reply #1 on: Time Format »

Sheet 3
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rnolan

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Re: MB-1 no output
« Reply #2 on: Time Format »

Do you get anything on the Loop sends ?  Also clean the Loop return jacks, they are serial loops and will break the signal chain before the output (they are switching jacks which can fail due to gunk/corrosion).  IIRC the direct out is just a split off the input jack, so before the gain, eq, etc.  The signal at the Loop sends (and they should always have signal) is after the gain and eq, so if you have signal there, then the issue is later in the signal path.
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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

MarshallJMP

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Re: MB-1 no output
« Reply #3 on: Time Format »

Do you have a scope?
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peoriashows

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Re: MB-1 no output
« Reply #4 on: Time Format »

Do you have a scope?

Yes, I have a scope I'm getting a good signal on many of the input components. I'll check the Loop sends tonight when I get home.  Thanks. That didn't even occur to me. Would they still effect the output signal if they're not turned on with the patch I'm testing with?
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rnolan

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Re: MB-1 no output
« Reply #5 on: Time Format »

Good question, I'm not sure, from the schematic it looks like any problems (bad contacts) in the return jack connections may break the signal path, @ MJMP, what do you think ?
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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

MarshallJMP

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Re: MB-1 no output
« Reply #6 on: Time Format »

mmm don't think so but you can check it by inserting a patch cable in both loops.

Best way to check is use your scope and start at the input and follow the signal to the output, something must be wrong somewhere.
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rnolan

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Re: MB-1 no output
« Reply #7 on: Time Format »

Also you get signal at the DI out, that can be switched pre or post gain stage etc.  So if you get a signal on both, pre is inst level, post is line level and the post line level (according to manual) splits off the main full range out so this may help narrow it down.
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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
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