PS2 3V Meltdown ???

 A short somewhere,could be a harness wire so check them when replacing board. Insulation off a wire could touch something.  Also could be a short in one of the board components such as a capacitor.   Sh** happens, not real common but it can happen with any PC electrical device. No fuse protection I know of in the boards,if it carried high voltage one would probably be used.. Just replaced the power supply board in a Vizio TV and it had a fuse.

At work,I used to have a job,I saw breaker panels catch fire, one by one in a chain,and I saw a door blow off a 4160 volt panel.  Saw transformers blow up and electricians with burn scars on their faces and hands.

Dale H

Hugh,

A pinched coupler wire will do some damage.  Did you recently have the shell off?

Keeping it on the track with power will damage it even more maybe to the point where the bottom board will need replaced.

Dave

I have seen this and simular problems many times and wonder if I might make a suggestion. Make an effort to treet and refer to all engines sitting on a track to which power is applied as "Powered Up" and those engines which you ahve started as "Started". In this example the above engine would be considered Powered up but not started. What's the difference? In this example the engine in question was ignored even though it was powered up. A Powered Up engine can burn boards.

Al

Guys,

The engine has not ever been worked on and there are no obvious pinches.

Dale,

I have TSV's on the outputs of my DCS controller. Is this 'the case' for putting them into each loco. If so, I have them. Where would you suggest they should be located. Most steamers have rollers on both engines and on tender, boards & parts in both.

The boards are the typical Proto-sound 2.0 3V boards.

Power Board MTH PN AE-0000011 (3vPS2) marked SCS 3V PS MTH Electric Trains.

Processor Board MTH PN AE-0000010 (3vPS2) marked MTH 3V SCS PROC RA.

Al, I don't understand your point here. How and why does a powered up engine which is dormant burn boards. That is the question. I am thinking it was a 'power up' spike.

At this point, it may be the time to have a MTH tech look at it.

As for the TVS locations, I put them in anything that has electronics.  For a locomotive and a tender, both with electronics, they both get a TVS.  They're cheap, and there's no real downside to having an extra.

The reason a Powered up board can still have and issue is that the Positive Voltage signal comes via the Rectifier from track power.  There is no relay that prevents track power from energizing the board.  It is sitting ready and does have DC current available to some of the circuits.  Shorting the coupler return lead to chassis ground would complete the current path and draw high current.

With one of your couplers trying to fire continuously tells me that FET is in a shorted condition or the wire is shorted.   More I think about it, the coupler wire could be the issue because it is under some mechanical motion under the truck or pilot.  At least on the tender, not so much for the front on an 0-8-0.  G 

Thanks Gunner!

I am an MTH Tech,trained but not active since my LHS shut down 3 years ago.

Place them across roller & ground???

Yep, right across the incoming power, center rollers to the frame.

The real issue with working on some of these boards is having spare parts to isolate what the issues are.  Of course, the board test fixtures would be useful as well.

I think if you don't have the materials to chase it down, sending it out is probably still the right call.  I've been amassing parts to fix most of my TMCC stuff, and usually it's pretty easy to deal with almost anything I come across.  I'm not in as good a shape for MTH, so I try not to cook them.

The TVS will NOT protect a PS-2 or a TMCC board for the matter from output problems.  The PS-2 output faults won't overload the Large rectifier or trip a circuit breaker, but it will damage the low current SMD devices and even in some cases the traces.  I have seen output faults short the board, but with current under trip conditions. 

The TVS may help protect the electronics from input problems.  G

Every little bit helps.  Obviously, I agree that even with TVS protection, there are lots of ways for the magic smoke to escape.

John You realize the MTH transformers have internal TVS across the output, so does DCS.  So the input side is pretty well covered especially if another is added across the DCS outputs externally.  Most of the PS-2 3V problems I have seen are on the DC ouputs via shorted speakers, smoke fan, tach reader, and light or coupler wire issues.  All the TVSs in the world won't prevent that damage.  G

Actually, I find that having the TVS inside the locomotive is the best place for protection.  Lots of stuff can happen between the TIU connection to the track and the locomotive itself.

Yes, I know that at least the Rev. L TIU has TVS protection on the outputs.  I'm not using an MTH transformer, so that doesn't apply, I'm using the PH180 bricks.

Such as what?  I thought the track the engine is attached to is also attached to the the TIU, we are talking about the speed of light right..:-)

Uh.....what's a TVS?

Clearly, we'll have to agree to disagree about the utility of TVS protection for each locomotive.  You do it your way, I'll do it mine.

David, TVS-Transient Voltage Suppression diode.

Well we really are not talking about the speed of light here. The fact is that any spike resulting from say a wheel jumping the track will progress at the same speed in both directions. It finally gets to the TVS which does it's job and clamps the spike at a safe level. Now that clamping action travels down the wire at the same speed until it gets to the engine where the start of the spike has already shown up and done it's damage. The idea is to get the TVS between the source of the spike and the device you want to protect.

As for the difference between powered up and started, as has already been mentioned there is no power relay or switch located in the engine. When power is applied the board and the electronics are turned on. The engine does not run and the lights and smoke are off but that doesn't mean there is no power there. The engine is not dead as in off.

Al

Gunner and G-cubed!

If nothing else, you must agree that my posts are thought provoking!

NOW! here is something worth checking!

"Most of the PS-2 3V problems I have seen are on the DC ouputs via shorted speakers, smoke fan, tach reader, and light or coupler wire issues.  All the TVSs in the world won't prevent that damage.  G"

David Bluegill

TVS = Transient Voltage Suppression or better understood as preventing random voltage spikes from one or another source from doing damage to other sensitive electronic components in the circuits. It is done with a TVS diode properly added to a circuit. GGG can explain it better, especially the spike origin details.

I gave up trying to explain why the TVS in the locomotive was the ideal location, even if there are ones at the other end of the wire.  I just didn't feel like launching into a discussion about the impedance of long wires and their effect in transient suppression devices at the far end.   I can say when I used TVS devices in aerospace applications, we didn't assume that just because they were on the outputs of a box, we didn't need them on the inputs that it fed.  EMI testing proved us correct, BTW.

Thanks Hugh!:-) 

Come on Al, ok 95% of the speed of light...:-)

John, We are talking track not small wires, nor are we talking about critical equipment needed to with stand EMP blast, possibly from a nuclear weapon:-)

Don't get me wrong I am not saying don't uses them, but I do question placing them in the every engine.  I have seen TVS direct short as the first failure.  Having that happen in an engine isn't going to be pretty to the wire harness.

My layout has the TVS in the Super snap terminal track strategically placed around the layout.  Plus the transformer output.  TVSs (plural) on the track will see that spike quite rapidly and suppress it.

I guess it would be nice to see one of the electronic gurus with the proper equipment run some test on a track with o-scope and measure  the action.

To me it is about risk management and reward.  I think the chances that the TVS in an engine saves the day when the others don't; versus the potential damage opening an engine and risking damage to the harnesses is far greater.

But as John states to each is own.  I just think an accurate discussion of the risk reward is worth the effort for the rest of the forum.

I can't speak to Legacy, but for early TMCC and plenty of PS-1 thru PS-2 MTH stuff (over 200 repairs in the last year) I can say maybe one or 2 attributable to unknown cause.  The rest where shorted motors over heating board, smoke unit failures, pinched harnesses, shorted speakers, tach readers and age.

The one caveate is the PS-2 5V which I do think had component level issues.  Some still run, others didn't last long.  G

I don't claim that a TVS in the locomotive is the cure-all for any issues with electronics, it's just one more bit of protection, and they're cheap.  I don't take an engine apart just to put a TVS into it, but if I'm already in there working, I stick one in as a little extra insurance.  As far as atomic weapons, I doubt the military trainers, biz-jets, or airliners that I built equipment for see much of that, at least I didn't hear about it.  Perhaps that's why we put them in the X-47 UCAV, but that's another story.

I have seen very few TVS failures, even during EMI testing of dozens of units, and field experience with many more.  I'm not really worried about them failing, I think it's far more likely that they'll help protect my equipment.

To properly measure what happens with a transient takes a lot more than the proper 'scope, it also takes lots of other equipment like the high current pulse generators so you know what conditions you're subjecting the test article to.  That's why we used to pay a ton of money to EMI testing labs instead of doing many of the tests in-house.

John, I haven't built those items, but I did supervise operation/maintenance and repairs to similiar equipment in the field for 31 years:-).  So I do know that the voltages and frequencies used, plus the components and their mil-spec ratings are much different then the TVS used on our 18V 60hz systems:-)

I have seen 2 TVS shorts.  One in a Z-1000, and one TIU short.

From my experience, long duration faults seem to cause an open on diodes and Silicon transistors.  Short duration faults seem to cause shorts, followed by trace damage.  No factual documentation, just experience on the repairs I have seen and my own stuff when tinkering. 

Good discussion for a Friday before the Forum goes down:-)  Would be interesting to hear from the manufacturers their thoughts as it applies to their board design and failure analysis conducted.  I know the QSI folks were worried about the spike effect on the large filtering capacitor on the output side of the FWBR.  G

I'm sure the 50 cent TVS diodes we buy aren't up to the specifications of the stuff we used in aerospace applications, that much is true.

I agree with your observations, I've seen a number of the little triacs shorted on the R2LC.  I'm actually on my second order of them to repair toasted ones, many are open, but I also find those that are shorted.

I don't doubt that many failures are internal flaws like wiring, I've been the victim of that myself more than once.  I'm a belt-and -suspenders kind of guy, as that was the most effective way of insuring a long MTBF in our designs.  There is no one solution to reliability, it's really a combination of many factors.  The TVS usage is just one measure that I feel has merit.  Better routing of the wiring is also very important, not to mention proper spacing and insulation of boards inside metal shells.

A long time ago Dale Manquen explained the TVS. It is not protection from shorts so it would not have helped in Hugh's case. However it does protect from spikes generated from short circuits. Imagine the spikes generated by a derailed car or engine being dragged down a track,even a modern breaker may not trip. If an engine derailed and was totally off the track,a spike generated off the motor would be protected with an on board TVS but not one down line across the transformer tap since it would not even be connected to the engine.  I would think if a TVS fails in the shorted mode,it would be uncommon but could happen. More likely it would fail and open. If one fails I think there would be a lot going on in the circuit and a lot of spikes.More are better but they do have a few pf capacitance so a lot of them may affect the DCS signal.

Speaking of nuclear attacks,I used to collect and repair jukeboxes and still have a few. In the 1950s most switching was done with solenoids and mechanical latch circuits. For a jukebox,100 selections meant 100 solenoids and some group solenoids. However the 1955 Seeburg V-200 used a Tormat memory unit using toroid magnets for switching. Really the forerunner to binary switching for computers.  When the magnet switch is pulsed with current in one direction the switch is on,pulsed in the other direction it stops. memory is permanent.  For its day this was cutting edge technology and used a 12AX7,6X4 and 2D21 vacuum tubes. The circuit had to be very precise and heavily choked against signal transients. Selenium rectifiers were problematic.  I read a long interview with the engineer who implemented technology he learned from WW2, a somewhat fascinating story if you like electronics.

Newer forms of solid state switching were later used in consumer electronics, however the military continued to use Toroid switching for a long time because it was not vulnerable to radiation from nuclear attack. The Russians also used and manufactured Vacuum tubes even into the 1970s,partly for the same reason,partly because they were behind in technology. Tubes are still used in some high end audio applications. Growing up in the 1950s,the government took the threat seriously and had a system of fallout shelters,I remember the drills in grade school and the Russian Premier pounding his shoe on the desk. Lionel had a Minuteman Missile car to respond so we were protected. So nuclear attack was and probably still is a design criteria.

Today the threat today is seeming less, but if a dirty bomb was detonated high above and area and spread radiation,most modern machines we depend on would cease to function. Most all cars would not start,but the old 49 Ford with points and a rotor and distributor would continue to run as would the steam engine the webmaster runs.

Dale H

Amazing the things we learn just because of toy trains as a hobby

Dale H Said: "If an engine derailed and was totally off the track,a spike generated off the motor would be protected with an on board TVS but not one down line across the transformer tap since it would not even be connected to the engine."

Dale,  I am not disputing the benefits of TVS, only pointing out MTH uses them in their transformers and TIU.  While your statement maybe true for an AC motor engine, I don't think this applies to DC motors and especially MTH PS-2 boards.

The TVS is across the AC input. While I agree if the train leaves the track, the Transformer and track TVS are no longer in play, I still don't see how the Engine TVS protects a DC Motor MTH engine.  The motor leads (spike source) are buffered by the Motor FETS, the relay with clamping diodes, the Full wave Bridge rectifier with large coupling capacitor and the inductors.  So a spike generated by the DC motor has free access to all the board components before it is ever clamped by the TVS connected across your AC input wires.  That is my original point.

The TVS on the transformer, TIU and those placed on the Track are less invasive and in my opinion complete protection for input induced spikes on the track.  Even if only 1 in 100 times does a diode short vice open, I would rather that occur on the track, vice inside my engine.  G

GGG

You could be right in this single instance, I am not an engineer. I never seen a schematic of the internal circuit of MTH PS2 boards.  As a tech,in practice we clamped as close as possible to the source of the spike. I remember one time I had to use 3 of them on a circuit to solve a problem. A circuit with a flashing light alarm actually used to punch out the memory of a computer in a meter system, resulting in dumping of thousands of gallons of caustic soda into a water treatment system..   Runs of wire has impedance perhaps making a downstream TVS less effective, and tracing flows of electrons is a complicated issue beyond my understanding. This is why diodes are placed across relay coils,clamping at the source rather than using a single TVS for the circuit.   Anything with inductance could generate a spike. Light bulb,smoke unit etc. not just the motor.

Dale H

There was a thread a wile back on one of the forums that seemed to go on forever about where to put a TVS. You could put them everywhere, where the power is connected to the track, at the transformer, or no where and let the manufacturer worry about it. It all depends on the protection you are looking for. It would seem to me that for personel protection the engine would be best but that is up to you. It would be nice if the manufactures took steps to protect their own equipment. Maybe they do but they don't say. All I know is we still have cases of boards from all manufactures going poof for no good reason. Most can be traced to those esternal shorts but there are still those that have no reason. One would think that the manufactures pay attention to these and try to find out what the cause is but I do not believe so unless it is a big problem with something new. The rest are just too expensive to pursue unless it starts to affect sales. That's just business.

Al

I think the reason is voltage spikes and maybe substandard components and design used. Only the now defunct K-Line really addressed the voltage spike problem.

MTH does put one in their TIU but that does not help conventional operators.

 BTW boards can be protected for external shorts if it is a design criteria.

Dale H

Way, way back when PS2 was first released and MTH participated on the OGR Forum they stated that PS2 boards had transient suppression in their design.  Transients are only one possible cause for board component failure.  Sometimes the smoke just gets out.  If you want much higher reliability you could always request military grade, stress tested, components. 

I have been lying here in the background just 'sucking up' the electronic know-how of our forum members. I saw no conflict here, just great diversive opinions on a complex subject.

I do have a plan for repair of my engine through all this with your help and will let you know how it all comes out eventually.

Hugh, It was rapidly becomming a Do'ed it argument, Nobody wins, nobody looses, no results. You do'ed it, No you do'ed it, No you do'ed it!!!

One may think that and can always opt out of the discussion. When a couple of knowlegable guys start swapping points of view, just sit back and listen. It is being carried out in a good friendly way and that is what counts.

here is one source

www.mouser.com/ProductDetail/S...giigmf73gBTH3RUsfEE0

Mount across the hot and common wires just like you are shorting it out

Dale H

The MTH boards are proprietary,without a schematic spike protection can not be verified. I never saw anywhere where a manufacturer other than K-line addressed the issue.

No one here implied that voltage spikes are the only cause of board failure. However it has become standard practice to protect solid state electronics from them. Every electrical failure has a reason but it is not always known or understood. Most likely train manufacturers do not care if a board fails after the warranty period,in fact they profit from selling new boards if they feel like stocking them. One reason I do not invest in these proprietary systems,no real competition or incentive to improve and you are at their mercy for pricing and parts from foreign suppliers.

Dale H

Thanks Hugh. I bet your glad to reach the end of all that!!

CHEERS MIKE