Electronics and DCC

 Sorry Cudaken, but.....

I told you so..........

.....about 2 years ago when I was asking you why you were running 8 amps with your DCC system.  I suggested going with something of quality, but you stuck with the MRC unit...........

David B

davidmbedard:

 Sorry Cudaken, but.....

I told you so..........

.....about 2 years ago when I was asking you why you were running 8 amps with your DCC system.  I suggested going with something of quality, but you stuck with the MRC unit...........

David B

Dave how stable is/are MRC units anyways? The problems I'm hearing about sound like spiking and if that is so then-----?

Randy, you may be right but my experience was that that may not necessarily be so. I have a couple of monoblock tube amps in my house that are over 20 years old and have worked even in places in the country where spikes, drops, brown outs and all manner of stuff occur and still have not blown anything, as well any other pieces of equipment don't pop like those. I'm always finding that you can't always say it is one OR the other. With my decoder in the SW1200 for example it would go south when the freezer clicked on. We put the whole train layout on another circuit --put a line condx/surge bar on line and no problems after that. And this was over at a friends layout--I've since done this on my own with same  results. Makes one wonder sometimes is all---

 Ken,

  You mentioned running part of your layout on DC.  Are you sure that the DCC and DC are not getting tangled up together somewhere?  That might create some spectacular failures as the two power sources would try to over power each other. 

  Other than that, I suppose it's possible your booster could be misbehaving, but the things that really destroy decoders are output shorts, like a motor lead getting shorted to a rail or to the other motor lead, or light outputs getting shorted to the common return or each other.  Is there any chance that wires are getting loose and bumping into conductive stuff inside the locomotives?  Pinched wires?  Uninsulated solder joints?  Unisolated or poorly isolated motors?  If this is one or two engines in particular, maybe the motors are taking too much current in stall, possibly bad motors.

  You might look into TCS decoders.  I am too embarrassed to send them decoders that I smoked in sheer stupidity, but I think they have a goof-proof warranty and would replace a decoder with an unexplained failure.  Besides, I really like their decoders.

   Also, some decoders are rated for more current than others.  You might need a heavier-duty decoder for a particular engine.

Jim

 Randy, 8 amps is not the problem, it is when the 8 amps are out of control, then there a problem. If I was not having a short, spike or just over taxed my engines then 8 amp should not cause a problem. I don't see any reason to think if there is a short, spike or over taxing my engines 5 amps would be more forgiving than 8 amps when decoders max is 2 amps peak. 

 Now this "something of quality" thing is something new you have added Randy. As far as I can remember you never said MRC is junk, just that it was to much power. If you have warned MRC lacks quality in there gear I would have but me heed to your warring's.

 Jim, I wish it could be that simple! But, my bench main lines are completely isolated from each other with plastic rail joiners on both sides of the rails where they interconect. Politary is correct and there is no problem when a engines crosses over to the other main. All the track is still DCC power, I have not hooked up the DC power supply to the B line yet.

 Randy and the other fine person that brought up the tail light fix again, thank you for the links. After reading the links I understand the fix better.

 Barry, a fellow audiophile! Are you a Mac Man? With the power my DQ 10's demand, I am soild state usining Adcom 555's bridge mono. I thought the DQ sounded good with a mer 200 watts a side, then I went mono blocked, it was turly hearing them for the first time after owing them for 21 years.

 Thanks for all the great efforts from the kind folks here.

                        Ken

 You are right about the amps, in a way. 5 directly applied would fry a decoder just as easily as 8, although since when teh breaker in teh booster trips, it SHOULD pulse on, if there's still a short, trip, rather quickly. I'm not sure how well the one in the MRC booster works. No, it's not 'junk' but I wouldn't rate it as high as a Digitrax, NCE, or CVP booster. It could be that it doesn't trip fast enough. A good test is the 'quarter test' - another reason the booster might not trip is if your wiring is not adequate and a decoder shorting across the tracks via the loco wheels only draws 7 amps - plenty to fry the decoder and melt plasctic but since it's less than the booster's 8 amps the breaker never trips! The quarter test will cost you 25 cents. Set a quarter on the rails, testing various parts of the track. If you set the quarter on the track and the booster trips, you're good. If it doesn't, you need to check the booster to be sure it works properly, and assumign that is the case, check the wiring - you may not be using heavy enough wire, or have enough track feeders connected to the bus. You shouldn't have to push down on the quarter,

                                             --Randy

 And if the booster doesn't trip fast enough, 8 Amps ought to be just about enough to weld the quarter to the rail.

The current capability of the booster is not the issue. The total current that flows is only that which is demanded by the load. If it only wants 1 amp, then the power supply supplies 1 amp, no more, no less.

If decoders are burning out, the probable cause is excessive current flow. A slow increase in current will not trigger any protection circuits in a booster. What could be causing that is a voltage drop as you move away from the booster. Or the booster has poor regulation, which causes the voltage to drop under load, and to satisfy Kirchoff, the current increases.

What needs to happen is a check of the power being put to the track as well as the wiring. Old DC wiring can cause problems too, by introducing a voltage drop. And the result is more current again.

Does the circuit breaker system work correctly (ye olde quarter trick)? Things like taillights being used as protection will also mess this up. Not to mention that the bright light may obscure your view of a smoking decoder. Excessive current over time will simply cause the decoder to get too hot, which will shorten the lifespan of the decoder. It isn't a spectacular failure, but it will occur in the future. Smoking decoders are much easier to diagnose than those that "just die".

 Randy, if you are ever near Maryville IL you have a places to stay for free.You have really tried to help and I appreciate the effort.

 On the wires, the runs are long due to the fact when I was wiring the then Slot Car / Train layout I only knew slot car track wiring. Plus I sit pretty far away from the bench and where I sit is where the command station and booster sit. Wires from the booster are 12 gage good quality speaker wire, around $1.00 per foot and 14 foot run and two sets of them. It started out as a 2 line blocked DC, I hooked A and B line wires to the booster and polarity is correct. (Real good stuff for my DQ 10 speakers is $16.00 per foot.) The wires from the booster go to 4 terminal strips. 2 strips are for the A line and 2 for the B line, each line has inside and outside strips for that line. By C line was hooked to the B line strips.

 Now this is where it gets messy. Remember, when I wired this I did not know about this great site or K-10 Model Trains was around. Feeder wires are 14 gage, but there is no bus wires. I ran wires from the strips to where they where solder to the rails. Some wires runs are a good 27 feet long. For slot cars, that was fine, I have some really nasty and fast cars but none will come to 1.5 amp draw by them self. I have feeders about every 6 foot.   

 Before you say the wiring is the problem and it could very well be! When the Bachmann E-Z only ran the the B line (A line was DC for 6 months or so before I got the booster) its breaker would kick in fast when there was a derail. When the E-Z was only running the B line it could power 3 sound BLI steam engines with some effort and 2 where easy. It was not till I made the A line DCC that I need the booster.

 I guess the first thing I need to do is test the booster tripping on the bench.

                                      Ken

 Only if I get to drive the Cuda

Definitely do the quarter test and make sure the MRC booster trips fast liek the Bachmann did. It sounds like the B line is probably OK if the bachmann tripped out quickly there, but if you've made any changes since then, test it as well. If you could run 2 and sometimes 3 BLI locos with the bachmann alone on the B line, but not run the same locos on the A line - there may well be wiring issues. The locos certainly don;t draw more power just because they are on a different piece of track. Now obviously if you ran 3 on B line and tried to run three MORE on the A line, there's be power issues with the 1 amp system, but JUST those 3 that ran fine on B should also run on A with the same power supply.

#14 might be pushing it a bit at 27 feet but if you have them every 6 feet of track you should have plenty of power. Not sure I want to know how you soldered wire as heavy as #14 to HO scale track though..

                                                   --Randy

The book says at 120 volts ac #14 is good for 45 feet at 10 amp for less than a 2% voltage drop, so I think Ken is safe.

Ken, can you tell me if the decoders actually get hot before failure or do they just fail?

Getting hot suggests an overload condition (for some reason) and just dying with no outside evidence of same suggests a spike frying its poor little brain, or perhaps confusing the decoder.

Shorts may be a solution, but the short has to be on the motor side of the decoder vice the track side, all its going to see if the track side shorts is its input voltage going to zero. Motor side short will cook it in a heartbeat. The spike from an incident of track side shorting might fry its little brain, however.

Doubt its AC flunctuation as the filtering inherent in an AC to DC recitifer would smooth most of that out, if properly designed and built. Note that a surge may have damaged enough of the power supply to let smaller surges through but not totally incapacited the unit. Thus what might not have caused a problem might now be causing a problem.

Solution would be put a power quality monitor ont he output of the command station and see if there are transient spikes over time. Don't have anything to do that here.

Jack W-NV0W

 Actually, the WORST short there can be would connect one side of the motor to the track - pretty much instantly smokes any decoder. Say if the motor is grounded to the chassis, and the loco derails and it pushes a wheel up in contact with the underside of the chassis - poof. It shouldn't be a problem in even old Blue Box Athearns if the install instructions are followed (which includes isolating the motor from the chassis), but there are othe rexamples of 'needs help', in paricular the P2K Alco switchers, they ahve an orange wire attached to the lower motor brush - the other end of which is screwed to the metal chassis. Oops.

                                              --Randy

Randy;

I agree. As I said in my post any short on the motor side of the decoder will almost instantly let the magic smoke out of the decoder, including any shorts in the lights that may be powered by the decoder. No amount of breakers, fuses, or other current limiting devices on the track side of the decoder can eliminate that issue, as the decoder acts as a very expensive, very fast acting fuse in those situations. Those devices are intended to protect the command station or power supply, not the decoder and the motor.

The problem that I have is the electronics in the command station are just as sensitive as those in the decoder, so a spike that affects the decoder by creating an overpotential situation should also affect the command station, as the spike has to get through that electronics first.

Ken, after thinking about this overnight I have two suggestions for you.

1) Remove the space heaters from that surge protector and place them, if at all posible, on another wall outlet. The fact that your audio equipment picks up the hash from their on and off operations tells me that they produce a sizable signal and you want them on the supply side of that supressor, not the load side. If this has been suggested before I apologize for repeating it. This will also allow some of the hash to dissipate, although not all of them.

2) Buy a ammeter and monitor them power draw of your loco's, just to insure you are not pulling to much power. This is a good method of monitoring the overall health of your loco and can help identify binding and other issues before it costs you a decoder. Just good insurance.

Jack W