MRC power packs and how to open one

[Slomopiot]

I have an MRC Tech IV 260 that's dead. MRC's Service Department will not look at it so I gotta do it myself. Does anyone happen to know if the fasteners that are used to hold the box together are some sort of oddball screw or rivets ? I've tried several Allen wrenches to no avail. . . .

[rich1998]

They should look like a Torx with a pin in the center. I use to have a tool that fit in a handle from an Xcelite set but do not remember the tool number. I found the bit at a local tool shop about twenty years ago. No idea where it is now.
I have seen this discussed in the trains,com forums and some know the tool number.
Some here might know. Best I can do.
MRC does not want customers opening it. I have read that in other forums. They will not cooperate.
Edit. It might look like an Allen screw with a pin. Been many years.

Rich

[James in FL]

IIRC for all MRC packs its a Torx T8-TR (tamper-resistant).

[rich1998]

Thank you for posting that. I think I had that hidden in my notes. I remember carying the box to a tool supplier in West Springfield, MA locally and they sold me the proper bit.

Rich

[Len]

With the hassles involved in trying to repair the Tech 4, which may turn out to not be repairable once it's opened, it seems a lot simpler to just replace it. The MRC 1276 Tech 7 AMPAC 760 has the same basic output ratings and controls as the Tech 4 260, and the price isn't bad.
https://www.modeltrainstuff.com/mrc-1276-tech-7-ampac-760-train-control-with-momentum-power-pack/

Len

[rich1998]

There was quite a discussion on repairing one on a trains .com site some time ago but you have to understand electronics, components and have a multi-meter. I looked it up. Depends.
Probably easier to buy a new one.

Rich

[Maletrain]

I just looked at the bottom of my Tech 7, and its version of tamper-proof screws are just old-fashioned slotted heads with a filled-in section in the middle of the slot.  Easy to make with the necessary tool with a regular screw driver and a Dremel cut-off to put a gap in its bit.  Why are they bothering?

[Len]

I just looked at the bottom of my Tech 7, and its version of tamper-proof screws are just old-fashioned slotted heads with a filled-in section in the middle of the slot.  Easy to make with the necessary tool with a regular screw driver and a Dremel cut-off to put a gap in its bit.  Why are they bothering?

To avoid liability and lawsuits if someone electrocutes themeslves, or burns their house down, messing around inside the case. Same reason there's usually a "Not User Repairable" warning somewhere on the case or box it came in.

Len

[James in FL]

To avoid liability and lawsuits if someone electrocutes themeslves, or burns their house down, messing around inside the case. Same reason there's usually a "Not User Repairable" warning somewhere on the case or box it came in.

Exactly why they are using Tamper Resistant screws.

Liability

[rich1998]

Liability. Mains voltage inside, Some might not unplug when working on it, believe it or not.

Rich

[Quentin]

Really? Wow, never knew that. By the way, every time that I've worked on one of those worked just fine after I was finished... Remember, I'm 16, so I could've done something that I didn't know I did.

Quentin

[rich1998]

Repairing is one thing. Not unplugging is another thing.
I have worked with electricity for at least fifty years. Maintenance and electrician.
I have read many times of people who came in contact with 120 AC mains power and ground. Some times something as simple as a metal case powered hand held drill that was shorted inside.
At 14 I was repairing vacuum tube radios and came close. I learned when I built my first shirt wave one.

Rich

[Terry Toenges]

I remember as a lad of about 11 or 12 deciding to see what the inside of a radio looked like and how it worked. I had it plugged and touched the wrong thing. It was quite a jolt I got.  It scared me but I was more afraid of getting into trouble with my Dad than I was of the shock so I never said a word.

[rich1998]

Many years ago radios did not have the two pin plug polarized. The chassis could be hot with respect to ground.
First lesson. I had built a Heath Kit volt, ohm meter which showed me.
Same thing with household lamps. Notice for some years, one pin larger than the other.

Rich

[Gary Allen]

I've been a EE for over 40 years, designing avionics, data acquisition, and test equipment.  I've done a lot of rewiring in houses (not part of my job).  Get sloppy every once in a while.  Probably been shocked with 120 VAC 20 times or more.  Just a little jolt as long as you're not in standing in water.  120 VAC is not considered lethal.  240 VAC on the other hand...  Worst shock was working on a light-sensitive plotter (old technology).  Got hit with 350 VDC.  Now that knocked be back.  Fortunately, the high voltage capacitor discharged pretty fast.

Looks like many of you are forced to perform reverse-engineering on this stuff.  I'm guessing there are little or no schematics or interface specifications available.  Do you have a web site where you post your reverse-engineered data?  Do any of you use a digital scope?  Looks like it would be invaluable while attempting to troubleshoot these circuits.