Triaxis modes: Lead Drive and Rhythm modes

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7enderbender

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Is it normal that the Lead Drives 1 and 2 influence the gain and output of the clean/rhythm modes? I was somehow under the impression that they shouldn't be doing anything in Rthm green and yellow - but they do on my unit.

Also, there is quite the volume imbalance when everything is set to, say, 5 and I switch between the modes. Normal?


EDIT: There is also quite a drop and thinning when going from LD1 green or yellow over to LD1 red. I found a few threads here that this could be a more serious defect that requires new cables and optocouplers or whatever. Serial is in the T69xx range - so I would think it's a TX4 version V2 non-fat (even though I was told otherwise by the previous owner stating it was more recent and with the fat mod).
 
I'm no expert, but a quick look of the Triaxis Schematic shows that they are using LDRs (Light Dependant Resistors, or Optocouplers) to do a lot of the circuit and component switching. These parts do wear out over time, leading to parts of the circuit not turning on and off as they should. It's a pretty common cause of weird behaviour in the Mesa Quad Preamps now that those are all 20+ years old.

I don't believe those lead controls should be doing anything in the rhythm modes, and the fact that they are means they're probably not being gated by those LDRs like they should be.

However, might not be too bad to double check the obvious things like tubes and maybe have a tech check for bad solder joints before biting the bullet and replacing all those LDRs.
 
IronSean said:
I'm no expert, but a quick look of the Triaxis Schematic shows that they are using LDRs (Light Dependant Resistors, or Optocouplers) to do a lot of the circuit and component switching. These parts do wear out over time, leading to parts of the circuit not turning on and off as they should. It's a pretty common cause of weird behaviour in the Mesa Quad Preamps now that those are all 20+ years old.

I don't believe those lead controls should be doing anything in the rhythm modes, and the fact that they are means they're probably not being gated by those LDRs like they should be.

However, might not be too bad to double check the obvious things like tubes and maybe have a tech check for bad solder joints before biting the bullet and replacing all those LDRs.
Click to expand...


Thanks. Yes, that's exactly what I figured. My unit does at least two things that it's not supposed to - 1. The drive settings influence the rhythm channels and the respective other channel for Ld1 and Ld2. 2. Ld 1 red is plain dead and barely puts out any gain at reasonable settings.

I actually called Mesa Boogie support and they confirmed this. It's going in for a factory service today. It's going to cost a bit but I figured it's worth it.
 
Just to close this out. I ended up sending it to Mesa Boogie. Indeed, some of the LDRs were shot or their way out and something was shorted out. A few more other small items were swapped. Whole repair including shipping was a little over $230. That seems reasonably fair. I don't have it back yet but will report back on more details and on the outcome.
 

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