I have 2 Atlas B 23-7 diesels (n scale) one is #49708 Sante Fe the other is #49731 ATSF (kodachrome). The 49708 has a black case on the motor and yellow lights on the DC board, the 49731 has a gray motor case and orange lights on the DC board. I installed an MRC 1811 sound DCC decoder in the 49708 and an MRC 1641 DCC decoder in the 49731. They are both programmed to the maximum voltage at top voltage (255 and 32). The 49708 dcc 1811 runs very fast (nearly leaving the track), but the 49731 dcc 1641 runs very slowly ( 1/4 to 1/3 of the speed) Do these 2 engines have different speed motors ( fast, scale, slow) or is the 1641 decoder not supplying the motor with maximum voltage ? I want to consist these 2 locos. Can anyone please help. So far no help from MRC or Atlas. Thanks
I don't have those locomotive models, but from your description it sounds like they may have been made by two different companies; possibly Kato with the black motor and Roco with the silver motor, so they may have different gear ratios.
Try adjusting the mid and max voltage settings on the faster locomotive to slow it down (CVs 5 [VMax] and 6 [VMid])
I do not use MRC decoders, but have read on these forums that they sometimes have very poor motor control.
I recently ran into a case where the VMax had to be cut down to less than 50% to speed match with another model, even from the same manufacturer.
These locos are both made by Atlas, with the same gearing, but one has the older motor while the other has the newer "ScaleSpeed" motor. you will have to slow down the faster loco by adjusting CV5 and 6 to match the speed of the slower loco.
DustyR I have 2 Atlas B 23-7 diesels (n scale) one is #49708 Sante Fe the other is #49731 ATSF (kodachrome). The 49708 has a black case on the motor and yellow lights on the DC board, the 49731 has a gray motor case and orange lights on the DC board. I installed an MRC 1811 sound DCC decoder in the 49708 and an MRC 1641 DCC decoder in the 49731. They are both programmed to the maximum voltage at top voltage (255 and 32). The 49708 dcc 1811 runs very fast (nearly leaving the track), but the 49731 dcc 1641 runs very slowly ( 1/4 to 1/3 of the speed) Do these 2 engines have different speed motors ( fast, scale, slow) or is the 1641 decoder not supplying the motor with maximum voltage ? I want to consist these 2 locos. Can anyone please help. So far no help from MRC or Atlas. Thanks
Google "speed matching DCC locomotives" and you'll get a lot of info. Be sure and use the prototcol for your MRC chips. I use a lot of Soundtraxx units and their's is different and so I use a computer to help. MRC I think are like Digitrax and so easier to do with max, mid and low voltage settings.
Check out the link below. If you want to use your computer to speed match, this program makes it a snap.
http://jmri.sourceforge.net/
DCC can't make a slow locomotive go faster. But, it can make a fast loco go slower. If those two locos were on DC they would likely run very different speeds. So, as said above you must match the slowest of the 2 locos after setting the max voltage to highest level on both. That way you know that each loco is running as fast as it can.
Richard
Yes, it could be the decoder -- MRC decoders are known to be extremely poor quality.
DustyRI got a third b 23-7 with a black motor exactly like the first fast one and when i installed the mrc 1641 dcc decoder it ran very slow also. Black motor and gray motor very slow 30-40 scale mph not scale top speed at all. Could it be the decoder?
A key question is, Does the loco run significantly slower with the DCC chip than before? A decoder cannot make a loco run faster. I always run/test the loco before installing DCC decoders, that way I have a baseline to know what changed, in which direction, etc.
It is pretty unlikely that you have different motors. The B23-7's didn't come out until well after Atlas switched to "scale speed motors"
Best way to get to the root of the problem is to reinstall the DC boards and test them out on DC. A 9 volt battery works as a DC source and the terminals fit on N scale track. Personally, I'd suspect binding in the slow engine. That's going to take some investigation to find. A DC source and a current meter are the best way to start looking for binding. Higher current readings will point to binding problems. Could be as simple as the frame screws being too tight on the slow engine.
Martin Myers
I tried to speed match them, but it is not the best because the start voltage # needs to be very near to the max voltage # on the fast speed motor. Atlas e mailed me that I have one fast speed motor (black case) and 1 scale speed motor (gray case) and that they still stock the fast #490100 (black case) motor. I may order one. The parts list in the box of both locos have the motor listed as part # 490100. Maybe someone had changed the motor in one of them before they sold it to me.
DustyRI tried to speed match them, but it is not the best because the start voltage # needs to be very near to the max voltage # on the fast speed motor.
It is not clear to me what you are doing. Are you saying that the starting voltage for the slow speed motor, CV2, has to be set close to the same level as the max voltage level for the fast motor, CV5? This doesn't make sense to me. CV2 should be set so that the locos move at the slowest continuous speed without stalling. CV5 should be set so that both locos move at the same maximum speed you want them to go.
I confess to not knowing much about N scale. However, I would assume (probably a bad thing) that the purpose of the slow speed motor was to get away from the "go like lionel" speed that I have been told N scale locos travel at. If the slow loco is actually travelling at a reasonable scale speed, I'd be slowing down the faster loco. So, exactly how slow is the slow loco?
DustyR i have to reduce the top speed on the fast one down from 28 to 14.
So, the max speed of the fast loco at speed step 14 is about equivalent to the max speed of the slow loco at speed step 28? Assuming that the decoders are capable and working properly, you should be able to reduce the value of CV5 in the fast loco so that the speed at step 28 is equal to the step 28 speed of the slower loco.