Mark Bass 121 Combo Issue

[Agent0]

I have a 121 Combo purchased in 2017. No issues until now. It is not heavily used and is well cared for. I played it a bit before leaving for a rehearsal and it was fine. When I got there and plugged in, nothing but low volume distorted sound. I tried the patch cable in the effects loop trick but it did not work. I then tried inserting a plug several times in and out of the effects jacks, and then it was fine. For good measure later on, I did that 20 times on all jacks with a couple of drops of Deoxit 5. Still fine ever since. I am hoping dirty jacks is all it was but then I wonder how it came on so suddenly, and why the patch cable didn’t work. Any ideas on this issue?

 

[SJan3]

I have a 121 Combo purchased in 2017. No issues until now. It is not heavily used and is well cared for. I played it a bit before leaving for a rehearsal and it was fine. When I got there and plugged in, nothing but low volume distorted sound. I tried the patch cable in the effects loop trick but it did not work. I then tried inserting a plug several times in and out of the effects jacks, and then it was fine. For good measure later on, I did that 20 times on all jacks with a couple of drops of Deoxit 5. Still fine ever since. I am hoping dirty jacks is all it was but then I wonder how it came on so suddenly, and why the patch cable didn’t work. Any ideas on this issue?

I don't have the answer but I like your "fix". I have a 2009 LittleMark lll and it did the same thing. Unfortunately I was told that it's the power amp board that needs to be replaced. Now I'm wondering about that as I gave the amp to a friend.
Regarding it coming on suddenly, if it's an electrical contact issue, I'd imagine there's no in between. Either it works or doesn't. Just an educated guess!

 

[Sparky Mark]

I don't have the answer but I like your "fix". I have a 2009 LittleMark lll and it did the same thing. Unfortunately I was told that it's the power amp board that needs to be replaced. Now I'm wondering about that as I gave the amp to a friend.
Regarding it coming on suddenly, if it's an electrical contact issue, I'd imagine there's no in between. Either it works or doesn't. Just an educated guess!

I will add that as Markbass effects loops are in parallel with the input signal, if the effects loop goes open circuit, the overall signal level drops by half. If the effects loop connectors become badly oxidised/contaminated but not completely open circuit then the 50% of signal passing through them could indeed sound distorted/ intermittent/crackly. This scenario does seem consistent with the OP stating that giving the effects loop connectors a thorough workout seems to have improved the situation.
Almost all instrument/line level signal connectors benefit from the occasional use to clear any contamination every so often, especially those permanently in the signal path.
My experience with the reported Markbass power amp board failure is that the amp either works or it doesn't. The first sign of trouble is the amp taking progressively longer and longer to turn on, to a point where it doesn't at all.

 

[SJan3]

I will add that as Markbass effects loops are in parallel with the input signal, if the effects loop goes open circuit, the overall signal level drops by half. If the effects loop connectors become badly oxidised/contaminated but not completely open circuit then the 50% of signal passing through them could indeed sound distorted/ intermittent/crackly. This scenario does seem consistent with the OP stating that giving the effects loop connectors a thorough workout seems to have improved the situation.
Almost all instrument/line level signal connectors benefit from the occasional use to clear any contamination every so often, especially those permanently in the signal path.
My experience with the reported Markbass power amp board failure is that the amp either works or it doesn't. The first sign of trouble is the amp taking progressively longer and longer to turn on, to a point where it doesn't at all.

That was my experience.

 

[Agent0]

That was my experience.

Thanks for the feedback. Fortunately nothing like that has happened yet. And just did a gig and still no further issues.

 

[SJan3]

Thanks for the feedback. Fortunately nothing like that has happened yet. And just did a gig and still no further issues.

To be fair, my LittleMark lll was over 12 years old with lots of use. I couldn't complain.