I have converted several older Atlas GP7's to DCC wdith that Digitrax board. The motor leads do indeed go onto the contacts in that notched area, and I just threw away that noise supression thing(I destroyed it one time trying to figure out what it really is....).
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Okay well, I had a nice little post all typed up, but it ended up being not all that appropriate. Long story short, my decade+ experience working with DC equipment tells me that there are some inaccuracies on this thread. However, your decoder/motor setup will work just fine with or without this sinister capacitor.
If you are curious as to the effects/differences then let me know and I can post some graphs and equational proof as to the inner workings of high and low freq PWM/SVFC. Best of luck to ya Jarrel!
Dave Loman
My site: The Rusty Spike
"It's a penny for your thoughts, but you have to put your 2 cents in.... hey, someone's making a penny!"
Sounds more like you are NOT onboard with me. The high frquency PWM from a silent drive or silent running or supersonic (ever DCC mfg calls it something different) is perfectly safe for ANY kind of motor - even delicate coreless motors. Low frequency, on the other hand - such as from cheaper or older deocders that do not support high frequency drive, MIGHT heat up a regular motor with continued creeping speed, WILL make the magenets in a loose motor like an Athearn 'buzz', and WILL damage a coreless motor.
The cap across the motor terminals will round off the square waves yes, but it will also interfere with the torque compensation used to offset the loss of low speed torque caused by the high frequency PWM. The result will be less then optimum running characteristics.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker wrote: What that is is yet another good reason to go with the board replacement decoder. Choke coils usually are in series with motor leads and supression capacitors are usually in parallel. So the best guess would be that that is a capacitor. Either way - the loco will run better with DCC if they are removed or bypassed, just like the ones in Bachmann locos. While they filter out high frequency harmonics that MIGHT interfere with your TV or radio, they also filter out high frequency from 'silent running' or 'silent drive' decoders. --Randy
What that is is yet another good reason to go with the board replacement decoder. Choke coils usually are in series with motor leads and supression capacitors are usually in parallel. So the best guess would be that that is a capacitor. Either way - the loco will run better with DCC if they are removed or bypassed, just like the ones in Bachmann locos. While they filter out high frequency harmonics that MIGHT interfere with your TV or radio, they also filter out high frequency from 'silent running' or 'silent drive' decoders.
I am sort of onboard with Randy on this one. It definetly looks like a capacitor. But the motor on a DCC engine is driven by PWM from an onboard H bridge so a cap wired in parallel with the motor would act to smooth off the edges of the square wave power applied to the motor, thus increasing the motor life. Creeping a loco in DCC is very bad for the motor as DC motors are okay with low volts, but not low RMS volts off a square wave. It will run with or without it. My take is that it should stay.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
I appreciate you guys looking and trying to identify the object. I wish Atlas would've put it on the diagram, the only piece of literature I got with the engine.
I think I'll go ahead and wire in the dcc decoder without it and see what happens. Heck, all I can do is let the smoke out of it...
Thanks again,
JaRRell
Hmmm, it looks like it is wired across the motor connections, so it would not be a resistor for lights. More than likely, it is a coil to suppress radio frequency interference from the motor brushes, but I have never seen a model from any manufacturer with one of these wired in separately. They're normally part of the board if they are required at all.
If it is an RFI choke coil, you could leave it where it is and see what effect it has on the decoder, but I would be more tempted to remove it if it were my engine. Many different Bachmann HO scale steam engines have RFI coils on their circuit boards to meet European interference requirements, which are more strict than US standards, and most decoder manufacturers recommend that they be cut off of the board during decoder installation.
jacon12 wrote:Here you go, Brian. I added more of a top view to it. Shoulda done that in the first place.Thanks,Jarrell
Here you go, Brian. I added more of a top view to it. Shoulda done that in the first place.
Thanks,
Jarrell
Hate to admit it, but now I'm not so sure. It kinda looks like that device (I'm not so sure now that it's a resistor) is attached across the MOTOR contacts.
I believe the following is the wiring (based on my Atlas C30-7, a couple of P1K C-Liners, and the DH163AO documentation at http://www.digitrax.com/ftp/dh163a0.pdf)
I don't recall what might be put across the motor contacts, and for what reason. Can't think of a reason for a resistor; perhaps a capacitor to assist in getting across bad track?
OK, I'm drawing a blank here, anyone else got a suggestion?
Brian Pickering
bpickering wrote: jacon12 wrote: I'm changing out the dc board for a dcc decoder in my Atlas GP-7, using the DH163AO, the only type I can find locally. The directions are straight forward enough, just replace the wires in the same spot and order as on the original board, but I'm wondering what this black thing is..My guess is it's a resistor and I guess I'm supposed to wire it onto the dcc decoder. Would that be correct?Your guess is probably a good one- this looks (from what we can see) to be an LED-for-lightbulb conversion, and dropping resistor would be required.A top-view might help, just to assure that we know where those wires are hooked to.Brian Pickering
jacon12 wrote: I'm changing out the dc board for a dcc decoder in my Atlas GP-7, using the DH163AO, the only type I can find locally. The directions are straight forward enough, just replace the wires in the same spot and order as on the original board, but I'm wondering what this black thing is..My guess is it's a resistor and I guess I'm supposed to wire it onto the dcc decoder. Would that be correct?
I'm changing out the dc board for a dcc decoder in my Atlas GP-7, using the DH163AO, the only type I can find locally. The directions are straight forward enough, just replace the wires in the same spot and order as on the original board, but I'm wondering what this black thing is..
My guess is it's a resistor and I guess I'm supposed to wire it onto the dcc decoder. Would that be correct?
Your guess is probably a good one- this looks (from what we can see) to be an LED-for-lightbulb conversion, and dropping resistor would be required.
A top-view might help, just to assure that we know where those wires are hooked to.
jacon12 wrote:I'm changing out the dc board for a dcc decoder in my Atlas GP-7, using the DH163AO, the only type I can find locally. The directions are straight forward enough, just replace the wires in the same spot and order as on the original board, but I'm wondering what this black thing is..My guess is it's a resistor and I guess I'm supposed to wire it onto the dcc decoder. Would that be correct?
and a more top view..