Author Topic: PM42 mechanical relay, problem?  (Read 1461 times)

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rsn48

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PM42 mechanical relay, problem?
« on: November 18, 2014, 02:22:57 PM »
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So I'm sure some of you are following the discussion at Model Railroad Hobbyist regarding circuit breakers, from least to best 1) light bulbs 2) mechanical relay aka PM42 3) electronic aka PSX and On Guard.

I've taken a response I gave at MHR and have posted it below.  What I'm wondering is with lower power usage in N scale are the following concerns legitimate, by this I mean, have people here experienced these problems on their layout and switch from PM42 to electronic circuitry because of problems, not because it was the best way to go?

And from MHR:
"I'm always leary when the new is best and the model before is now not so good.  I was curious about PM42's versus electronic circuit breakers, is there really that big an issue.  And is it that big an issue in N scale, so I did a wee search of the net:

1. PM42's failing - "Our club in SW Florida installed 13 PM42's in 2004. Over the years we have seen half fail. Some due to electronics and others were relay contact problems. Our layout is large and relays over time will fail due to load and arching of contacts during short circuits.Today we are half way through converting to PSX and PSX-AR units. All the installed PSX and PSX-AR's are functioning great. We have added Sonalerts and Remote Status LEDs indicators.We especially enjoy being able to run 4-5 QSI engines on one power district. This was not possible before. They would not restart on the PM42 after a short.I've been an electrical engineer and involved in electronics for 50 years. The Command Stations/Boosters and circuit breakers/RL controllers are the base of the DCC infrastructure. Over time infrastructures must be upgraded or expanded. This is what I see in converting from the PM42 to the PSX and PSX-AR modules. The new modules are solid state and are designed for the higher current demands of today's DCC engines. Happy customer, "
- Lee D.

2. PM42 voltage spike: ""I have personally seen a number of decoders reset (sometimes partially, sometimes completely) following a short circuit. One explanation I have heard (but have yet to test personally) is that the scramble is often the result of a strong voltage spike when that energy is released. As a side note, I have only seen these spikes happen when using PM42s and not when we switched to PowerShields, and after that, not since upgrading to the PSX breakers."
- Doug B.

I am not defending PM42's even though I have two on my layout, but I will say the above two issues I haven't run into locally with Digitrax users here.  I don't have any PSX's on my layout but I do have two On Guard - Auto Reversers (they are electronic) which are the poor man's PSX-AR and I'm happy with those, will be installing a third soon.

With the PM42's I'm wondering if this issue is less in N scale, with less power demands and or should I say 'consumers.' "
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Bendtracker1

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Re: PM42 mechanical relay, problem?
« Reply #1 on: November 18, 2014, 09:02:42 PM »
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2. PM42 voltage spike: ""I have personally seen a number of decoders reset (sometimes partially, sometimes completely) following a short circuit. One explanation I have heard (but have yet to test personally) is that the scramble is often the result of a strong voltage spike when that energy is released. As a side note, I have only seen these spikes happen when using PM42s and not when we switched to PowerShields, and after that, not since upgrading to the PSX breakers."
- Doug B.

In regards to what Doug B. says.

This is looking like what my problem may be stemming from.  I say this as I've had some problems over the past several years with decoders changing their settings/CV's for no apparent reasons.

I've talked to a few here on RW and several on other boards with not much success in fixing the issue.  However another member on another board who's been helping me on an off since the issue appeared mentioned something this summer about it could be caused by my PM42's

Several ago when it started, I had just put down some of those foam interlocking mats around the layout.  I posted it on my blog and here on my layout report and Phil D. sent me a response promptly saying that a friend of his did the same thing and was noticing he had a lot of static electricity afterwards.  Before he replaced the foam with carpet remnants he lost a DT4xx throttle, a panel and maybe some chips, can't remember exactly right now.

I've kept track of this issue of my chips resetting and it's boiled down to the winter months, which is when it gets very dry here in NE.  As soon as it gets dry, I notice a larger build up of Static Electricity will discharge if I touch anything metallic, including the tracks.  I've gotten into a habit of touching anything metal while working on the layout during this time and have also been trying to find a way to reduce the static build up as I really want to keep the floor mats.

Last summer I was talking to the member on the other board who's been helping me and he asked me if I had any kind of circuit breakers for my layout?  I told him that I had two PM42's.  He responded that these might be the culprit as they are not the best from protecting against things like static discharge.  He told me to look in to the PXS units if I had the chance. 

He wasn't going to guarantee this was the issue or that the PSX units would solve the problem, but said to keep an eye on it this winter.  Well sure enough, just like clock work, the static is back and I had a couple of chips act squirrely again.  I plan to change these out with the PSX units, or at least take a closer look at them.

Other than, the PM's have served me well.



 

rsn48

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Re: PM42 mechanical relay, problem?
« Reply #2 on: November 18, 2014, 09:37:51 PM »
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Interesting, so here locally at the Wet West Coast, static electricity isn't as much an issue due to higher humidity during the winter "dry" season.

If you change out to PSX's, could you post the results here to see if you still have decoder problems or not.

Thank you.
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Bendtracker1

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Re: PM42 mechanical relay, problem?
« Reply #3 on: November 18, 2014, 09:54:20 PM »
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Sure, be glad to, but it might be awhile before I get to that point.  If nothing else check my blog or subscribe to it, as I will definitely post there if I resolve the issues.

The issues with the decoders have been driving me nuts over the last several years as I have stumped everyone who has tried to help me resolve the issue, including Digitrax.

I remember him telling me that something abou the PSX units absorb charges or spikes?  I don't see these making a difference, but stranger things have happened.