Mark IV replacing volume knob - Possible to do at home?

[j0l]

I have managed to sausage finger the push/pull knob of my lovely Mark IV Mesa Boogie. (well the boot of my car did) & have sourced the replacement pot from Mesa themselves.

Is this the kind of repair that I can do simply at home? It looks like there are two points to solder. If so any tips on dis-assembling?

I'm not mechanically too bad, and I'd like to think I know when to stop but is this straightforward? I'm not great at soldering but with some patience and my reading glasses on I can probably do this.

Thanks

Jol

 

[dtrax]

Replacing a pot is simple. Just note which wires connect to the input, wiper and ground lugs and you're good to go.

BUT, tube amps are high voltage devices and can hold a charge (somewhere in the range of 450VDC) after they're powered off. In an amp like a MarkIV, there are bleed resistors that will dissipate this voltage and will normally be safe to work on the circuit within a minute or two. However, you should never blindly trust that bleed resistors are working as intended; you must confirm voltage has dropped to safe level (personally i shoot for under 10VDC). Personally I just use a 1K 10W resistor and it drains the caps in seconds, as would any tech. And it should probably go without saying, but absolutely make sure the amp is disconnected from mains power.

For your safety, it's probably best to have a tech do it.

 

[dradrachirgnildoc]

Should be an easy fix as long as you're careful with the HV inside the amp being absolutely safe.

I have broken most of the push-pull pots on my Mark IV and fixed them in a variety of ways (disabled the Pull Silent on the Master Volume control, hard-wired the Lead Fat ON as the knock that broke that pot shaft annihilated the switch).

Some of them are awkward to get at, due to how much stuff is crammed into the chassis.