[:(!]Murphy’s law is at it again! Anybody know Murphy? I’d like to ***!!@#$%. Any way, anyone know what could be the problem here? Digitrax not working. I measured the voltage from the power in terminals on the DB150 and they both read 9.6 volts. I measured the Rail A and Rail B terminals and they both read 7.5 on the HO setting. That equals 15 volts. (7.5 x 2) Here’s the kicker… Next I measure the voltage on the rail with the Rail A feeder from the track to the Rail A terminal disconnected One rail (Rail B which is connected to the Rail B terminal is 7.5 volts. But, the other rail, (which is disconnected at the Rail A terminal) reads 20.5 volts! Anyone know what can cause such a difference? The yellow adjuster screw inside the DB 150 is turned all the way down. The power surge seems to come from the track itself, as voltage in and out of the DB 150 checks out o.k. Thanks much.[:D]
O.K. I disconnected my 12v 500ma adapter that powers my switch machines and now both rails read 7.4 volts. I think I’m on to something. I’ll check my switch machines. I just hope I didn’t fry my poor locomotive.[oops]
Yow! This must be very Digitrax-specific. The answer, since Caeser, is “Divide and Conquer.” Isolate the turnout controllers and the track. Isolate the various power districts. Break the problem down into smaller and smaller problems. Now, (switching to Galaxy Quest), never give up, never surrender…
7.4 volts seems very low to me, but I’m a Lenz guy. Unplug everything from your controller, and check that first. AC voltage should be at least 12. If the world is unplugged, then your Digitrax is in trouble. If not, then add parts one by one until the problem comes back.
In my experience, Murphy was a bloody optimist!!!
Darrell, DCC-less, and quiet…for now
First thing is you have to have the right meter. A regular multimeter will not measure DCC correctly.
If your VOM meter is not capable of reading true RMS voltage then purchase an inexpensive digital Volt-Ohm-Meter.
Most of the analog VOM’s CANNOT read DCC voltages correctly.
Most DIGITAL vom’s CAN read DCC voltages correctly.
Such meters can be had for under $20.00.
It was named after Capt. Edward A. Murphy, an engineer working on Air Force Project MX981, (a project) designed to see how much sudden deceleration a person can stand in a crash.
One day, after finding that a transducer was wired wrong, he cursed the technician responsible and said, “If there is any way to do it wrong, he’ll find it.”
The contractor’s project manager kept a list of “laws” and added this one, which he called Murphy’s Law.
Actually, what he did was take an old law that had been around for years in a more basic form and give it a name.
Shortly afterwards, the Air Force doctor (Dr. John Paul Stapp) who rode a sled on the deceleration track to a stop, pulling 40 Gs, gave a press conference. He said that their good safety record on the project was due to a firm belief in Murphy’s Law and in the necessity to try and circumvent it.
Aerospace manufacturers picked it up and used it widely in their ads during the next few months, and soon it was being quoted in many news and magazine articles. Murphy’s Law was born.
The Northrop project manager, George E. Nichols, had a few laws of his own. Nichols’ Fourth Law says, “Avoid any action with an unacceptable outcome.”
The doctor, well-known Col. John P. Stapp, had a paradox: Stapp’s Ironical Paradox, which says, “The universal aptitude for ineptitude makes any human accomplishment an incredible miracle.”
Nichols is still around. At NASA’s Jet Propulsion Lab in Pasadena, he’s the quality control manager for the Viking project to send an unmanned spacecraft to Mars.
courtesy Askjeeves.com
That’s the way I understand Murphy’s law also. Popularity often leads to misuse.
I think what No1 Rail Fan has run up against is Sod’s Law rather than Murphy’s. Sod’s Law is along the lines “if there is a possible unfavourable outcome, that is the one that will eventuate.” Simpler language “if anything can possbly go wrong, it will.”
As to #1RF’s topic and comments regarding meters, I go along with caellis. There is a good article on meters for DCC in the Australian AMRM that says basically the same thing with a lot more explanation. Pity it’s not on line. Bottom line: you can use many less expensive meters as long as they are digital.
Your first reading is the key here. You should have WAY more than 9.6 volts at the input terminals of the DB150. This can be either a DC or AC source - standard sine wave AC that you can measure with a normal meter, so there are no issues with square wave DCC signals at this point in the system. You can’t get 15 volts out with only 9.6 volts in. What are you using to power the DB150? An old power pack? Or a proper power supply like the PS515? Proper input voltage across the power terminals coming in to the DB150 should be around 15 volts to be able to use the HO or N scale setting.
You appear to be using the trick of measureing Rail A to GND and Rail B to GND and adding them. This works fine - as long as you don’t have address 00 selected at some speed. They should be equal or close. If not - call up address 00 on a throttle and make sure you set the speed to 0 and then dispatch the address.
As to how your switch machine power is getting to the track - are you using stationary decoders, or just toggles and Tortoises? If that 12v supply is going right to switch machines liek Tortoises - perhaps you have a wire touching on one of the Tortoises, the outer terminals which are the motor leads touching one of the switch contacts - if you are powering your frogs. There’s really no other possible path unless you connected the fixed 12v supply to your track bus somehow.
–Randy
Um, the Viking landers were launched in 1975…
AskJeeves doesn’t appear to be too up-to-date. [:)]
Brian Pickering
In the computer programming business there is a Murphy’s corollary which says “mistakes are never discovered before a fatal error takes place” Of course we are talking about an operator’s mistake - never a programmers. Programmers never make mistakes!!!
Nope, programmers never make mistakes…
they just make undocumented features!
[(-D]