Apeks MTX-RC Servicing

[rsingler]

The MTX-RC is an extraordinarily difficult reg to start on, especially with no prior training. While it bears passing similarities with the XTX200, it has reassembly quirks that make it very easy to break a part. I'd REALLY recommend getting an old XTX50 to play with before you tackled this just from a manual.
Just for starters, the manual already assumes you know pick technique and torque application. The MTX-R requires simultaneous mounting in a vise and addition of the barrel nut - something not required by ANY other model. While the RC no longer requires that, I can't see that they've strengthened the case. That speaks to the delicacy of the case plastic. This is a reg for experienced techs.

 

[jzlassme]

It has reassembly quirks that make it very easy to break a part.

Can you elaborate a bit more which part I need to be extremely careful?

The MTX-R requires simultaneous mounting in a vise and addition of the barrel nut.

I already got the special tools from scuba clinic to remove the environmental cap and diaphragm clamp. I will start to service with my XL4 first to get some experience.

@rsingler Besides air leak, IP, lever height, and cracking effort. Anything else I need to add to the QC list to validate my work?

 

[rsingler]

Confirmation that when you bang on the purge button with no mouthpiece attached, the reg freeflows like mad until you cover the opening with your thumb. That's the dynamic confirmation that the lever height and cracking effort are enough to generate enough Venturi to pull the diaphragm in completely, locking the valve open.

And when you said "IP", it's more than just the value.
It's crispness of lockup (how many psi of drift with a new seat until it really locks up?).
It's dynamic IP drop on a normal breath at low tank (500 psi).
It's dynamic IP drop on full purge with a full tank.
Not all of these are in every manufacturer's manual, yet all are important things to know as a tech to confirm your reg is optimal. If you look at all brands, every single one of these factors is in somebody's manual.

And I didn't mention exhalation effort on the magnehelic. Only a few mfr's specify, but less than 0.6" is good.

And lever height - is it some "average value" as defined by a cheap plastic gauge or a ruler, or is it actual height of that reg's lever under that reg's diaphragm when pressurized as determined by a "tap-tap" estimate of separation?

 

[jzlassme]

And lever height - is it some "average value" as defined by a cheap plastic gauge or a ruler, or is it actual height of that reg's lever under that reg's diaphragm when pressurized as determined by a "tap-tap" estimate of separation?

Just want to make sure I get the concept right. The perfect height of lever is at the edge of no free flow when pressurized after orifice seat fully break in?

 

[admikar]

Perfect height is whatever is perfect for you

 

[rsingler]

Just want to make sure I get the concept right. The perfect height of lever is at the edge of no free flow when pressurized after orifice seat fully break in?

That's one definition of cracking effort - "at the edge of freeflow", though it might be a touch light and freeflow a bit when you look straight down in the water.

Lever height is mechanical: "maximum height within the case when pressurized" allowing for a tiny separation to avoid inadvertent triggering due to chance pressure on the faceplate. The lever usually drops 0.5mm when the reg is pressurized, which is why testing under pressure is the best technique.
You want maximum height for the size of the case and the configuration of the faceplate/purge button, to permit maximum valve opening. A lower lever only penalizes you, which may be dangerous at depth due to higher gas density.

 

[qc950216]

i have the MTX.R first ans second if it helps.

May I have the manuals also? Been wanting to service my MTX RC recently. Thanks.

 

[NuttyGriffin]

i have the MTX.R first ans second if it helps.

Would you be able to share it the service manuals please and thank you.

 

[Tipe]

I would also like to have a copy of the first stage service manual, if someone would be so kind to share it to me.

 

[inka]

Would you be able to share it the service manuals please and thank you.

DM sent