How do you measure current draw?

[Mark R.]

You sure didn't pick an easy engine for your first installation ! The first GP30 I did was a real head scratcher at first. The entire chassis has to be broken down and the frame halves separated. Once apart, you'll see where the motor is grounded to the one half.

These contact points need to be cut short and have wires soldered to them. Be careful when re-assembling the two frame halves. There's very little room to snake the motor wires up to the top of the chassis - you don't want them to get pinched and short out.

Once you get that one under your belt, everything else will be a breeze in comparison.

Mark.

[Chessie Sys. 3022]

 Thank you for everyone's help. I've decided to just install the decoder since I know the engine is only at most two to three years old, so I doubt the draw will exceed the 1.5 amp limit of the decoder. It's coming in tomorrow, along with my Digitrax Zephyr, so this will be my first decoder installation. Hardwiring, too! I hope it goes well - I'm excited to start using DCC!

[Hamltnblue]

Chessie Sys. 3022

 I'm about to order a decoder for my Spectrum GP30, but I'm not sure which one to get because I don't know it's current draw. How would I measure this? Thanks!

Here's a thread that talked about putting a decoder in a Bachmann GP30.  Take note in the last entry of the thread.  The poster notes that the motor required isolation since the frame was used as a conductor.  I don't know if it applies to you but if it does, failure to isolate the motor could burn your decoder.

http://cs.trains.com/trccs/forums/p/171822/1886152.aspx

[richg1998]

Get a cheap digital multimeter from Harbor Freight. These cheap meters have a 10 amp scale. which is what I use. I have three of these meters. Don't let rivet counters talk you into a expensive meter. If you make a mistake using the meter, less cost to replace.

Set the DC volts at 12 volts and with the drivers slipping, measure the current. Follow the instruction book for the meter or search the 'Net for using multimeter model railroading

You will get many hits. 

Many HO locos do not draw over 1 amp, usually a lot less. All my HO Spectrum's draw no more than 0.5 amp. 

The below fellow has a lot of good info.

http://www.members.optusnet.com.au/nswmn/index.htm

Rich 

[modelmaker51]

Any recent (last couple of years) decoder will work, nearly all of the H0 decoders from NCE, Digtrax, TSC etc are suitable power-wise for a Spectrum drive, just pick one you like. Power issues generally come up old Athearns and larger scale locos.

[locoi1sa]

 You install an amp meter or a DVOM that registers at least 3 amps to one lead of your DC power pack to your track. Turn the voltage all the way up so the locomotive is at its highest speed. Hold the loco still and apply pressure to the rails to stall the motor and look at the reading. Buy the next size up decoder and you should be good. If the stall current is under 1 1/2 amp then get a decoder that matches it or exceeds it. Most recent HO and even some N scale decoders will take a 2 amp load temporarily.

     Pete

[Chessie Sys. 3022]

 I'm about to order a decoder for my Spectrum GP30, but I'm not sure which one to get because I don't know it's current draw. How would I measure this? Thanks!