Question about Mark IV knobs...

Hi all, new poster here.

I have been looking for a Mark IV combo. I played an 'A' yesterday, and really liked what I heard. The amp seems to have a few miles on it, and has a broken channel volume pot on the lead channel. You can still twist it with your thumb, but the knob is gone. Also, the reverb sounded a little funky / noisy when it was turned up high. Not knowing the innards of a Mark IV, would these be expensive fixes?

I started looking because I heard a friend play through one at a gig and was blown over. I've never been a fan of Mesa gear much in general, but I think that's mainly because my exposure to it first hand has mainly been Rectifier amps, which I don't like at all. I need a new amp, and the Mark IV combo looks like something I would be really happy with.

Also, a general question... some of the knobs (knowing they have plastic shafts) seem 'loose' in that you can wiggle them back and forth. Is this a sign of trouble, or is it normal for these amps? This amp is marked $1350 at the store. I also found a wood / wicker combo, but that's a more recent version. I'm leery of buying that model without playing it, since the one I played yesterday did sound really good - just concerned about what the repairs might cost me. Should I not be as concerned about the tonal differences between the older and newer model? To me, there's nothing better than being able to plug in to the amp in person before buying it.

Any thoughts / insight would be greatly appreciated.

I have owned several Boogie amps and have replaced knobs before. I ordered my knobs direct from Mesa, they are very cheap and easy to install. The pot shafts are metal, not plastic. The small knobs are held on by metal clips. Large knobs are held on by screws. My Mark IV is like new, so I will use it as a point of comparison. The only knobs that have slack in them are the knobs on the push-pull pots. You can gently touch these knobs and they do appear to be slightly loose (my Mark III was the same way), but once you actually turn them they are fine. In my experience, this is normal, because the pots are of a push-pull design. All of the other pots are tight and show no sign of being loose.

I would check the push-pull pots to see if those are the ones you think are loose. In addition, pull them out and see if all functions work properly. I cannot comment on actual pot fixes and costs, but you could probably do it yourself since the pots are connected to the pcb with flying leads (no direct to pcb soldering). The pots themselves are probably not expensive. If the amp is ok buy it and order some new knobs direct from Mesa. If you have any experience with a soldering iron you can probably fix the pots yourself as well.

JeffMN said:

has a broken channel volume pot on the lead channel. You can still twist it with your thumb, but the knob is gone.

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I recently replaced the (pull) gain knob for my m4's lead channel. The part was around $10 from Mesa. It was a little bit of work to replace it, since it's on the lower row of knobs and they're packed in there pretty tight. Not too hard if you're good at that kind of stuff, but I have fat fingers, so it was a slight challenge for me Also, I wouldn't try it unless you're good at soldering and all that...

Should I not be as concerned about the tonal differences between the older and newer model?

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most around here say that the difference is very small between the a's and b's...

MarkofXlnts said:

I have owned several Boogie amps and have replaced knobs before. I ordered my knobs direct from Mesa, they are very cheap and easy to install. The pot shafts are metal, not plastic. The small knobs are held on by metal clips. Large knobs are held on by screws. My Mark IV is like new, so I will use it as a point of comparison. The only knobs that have slack in them are the knobs on the push-pull pots. You can gently touch these knobs and they do appear to be slightly loose (my Mark III was the same way), but once you actually turn them they are fine. In my experience, this is normal, because the pots are of a push-pull design. All of the other pots are tight and show no sign of being loose.

I would check the push-pull pots to see if those are the ones you think are loose. In addition, pull them out and see if all functions work properly. I cannot comment on actual pot fixes and costs, but you could probably do it yourself since the pots are connected to the pcb with flying leads (no direct to pcb soldering). The pots themselves are probably not expensive. If the amp is ok buy it and order some new knobs direct from Mesa. If you have any experience with a soldering iron you can probably fix the pots yourself as well.

Click to expand...

Exactly the info I was wondering - thanks!! Yes, not all knobs on the amp have that 'loose' feeling to them, to my recollection it was the push / pull knobs that gave me that vibe more than any others. I'm pretty well versed with a soldering iron, so that type of stuff doesn't necessarily scare me.

The lead channel volume pot that's broken, you can see the part of the shaft that's left... it looks like black plastic? Either way, no big deal... it still needs replacing, I just swore it was plastic.

So, this one is $1350. I found a wood cabinet one for $1650 too, that's a more recent version though. People seem to think that as the Mark V gets closer to street date the Mark IV used market will speed up and possibly drop in price. What do you guys think the chances of that are?

The non push pull shaft pots run $2.50 to $3.00 from mesa, the knobs run about $4.50 I just ordered some last week.

But be forewarned, Mesa bones you on shipping. I was charged almost $11.00 for shipping via UPS ground, less than 1 pound from Petaluma to Detroit, $19.40 for three pots, and two knobs and a receptacle bale and washer.

My total for the parts minus the shipping was $19.00