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Premium Member
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Discussion Starter #1
Hello all,

I have put a digitrax 583 in an Accucraft Heisler And I am having a strange problem. Under DC it runs just fine but under DCC it runs very slow. I have set my DCC at 17.5 volts which is above my 16 volts I am using on the DC system. Any ideas?
 

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Super Modulator
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20,517 Posts
First, you need to realize that electric motors get their speed from the "last few volts".... i.e. they are not linear. I raised my DCC track voltage about 2 volts and the top speed of my E8 went from 65 to 92 smph. Read this over until you get the fact that this was only 2 volts to the motor.

Also, in order for you to know your DCC voltage, you need a special RMS meter or oscilloscope to accurately measure this, what did you measure it with?

The real information here is that you need to realize that a decoder drops 2-3 volts from the track voltage. That's enough to make a significant difference in the top speed.

Even if your DCC voltage measurement is accurate, you would be sending 0.5 to 1.5 volts LESS to the motor under DCC in your scenario.

Hope this is a clear explanation.

Greg
 

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Discussion Starter #3
Greg,
I am using a RRAMPmeter to measure the DCC voltage and an Fluke Digital to measure the DC voltage. The DCC comes in 17.5 while the DC is at 16. For the DCC I am using my NCE Pro and for the DC it is an old Aristocraft supply. Now interesting enough that the Heisler seems to take only about an amp to run it. Both were fed to the test track.
 

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Super Modulator
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You are saying that with the decoder installed, it runs much slower on 17.5 DCC than 16 on DC, and both cases are with the decoder installed?

That is a stumper, I cannot believe that the "analog power conversion" mode can bypass the input diodes and the output transistors, but it almost sounds like it.

Make sure CV5 is at max.

Greg
 

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Discussion Starter #6
All,
Thanks for the tips, i will try them and see what happens. Yes, it is very strange and it's only with the Heisler.
 

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Discussion Starter #7
oh, by the way, all CV's are at default as this was a new unit right out of the bag.
 

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Discussion Starter #9
Greg,
i have to admit, if I can get sound out of this 583 then i have really accomplished something! LOL
 

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Super Modulator
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Interesting.... I forget if the Digitrax has bemf.... are you saying this same decoder in a different loco does not have the same speed differences?

Can't believe that the motor in the heisler could be the problem, normally they are pittman and don't draw a lot of current.

hmmm....

Greg
 

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Discussion Starter #11
Greg, I did not try this decoder in another engine, however I had an old MRC that I thown in the Heisler before and it experienced the same stuff so I figured to replace it with the Digitrax.
 

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Super Modulator
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Hmm... I have a number of MRC, and they aren't great, but getting similar results points to the motor.

I have a completely different idea, maybe there is some electrical problem where the motor is not completely isolated from the track pickups...

Another idea is to measure motor current, could the motor be in a condition that the DCC decoders cannot deliver enough current?

Very strange... worrth doing the current measurement in both DC and DCC

Greg
 
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