# Power Buffer and NCE 408



## supagav (Feb 8, 2008)

Hi, 

I'm currently using a Massoth 1200Z with two wireless Navigator handsets. My USAT 44 tonner has an NCE 408 decoder fitted inside along with a Pheonix P5. This loco occasionally stalls on a few of my larger radius points when it crosses the frogs. I was thinking of using the Massoth power buffer to get round this problem, is it possible with this particular decoder please? Has any ever used it or had any experience with it? 

Any help or advice you could give me would be greatly appreciated! 

Thanks, 
Gavin 

ps: here is a link to the PDF manual for the decoder: 
http://www.ncedcc.com/d408srv35.pdf 

and the power buffer: 
http://www.massoth.com/downloads/handbuch/8151001_v110.pdf


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## Road Foreman (Jan 2, 2008)

Gavin, 

I would get a 2200 to 4700 ufd capacitor & install it across the bridge rectifier +/- terminals.. 
I think this would be easier than the power buffer.. 

BulletBob


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## supagav (Feb 8, 2008)

thanks for your reply Bulletbob, 
I've got some capacitors handy, but how would I hook it up? When you say the bridge rectifier terminals +/- what exactly do you mean? Sorry for my ignorance, thanks again. 
Gavin


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## Road Foreman (Jan 2, 2008)

Gavin, 

Ask NCE where the bridge rectifiers +/- points are.. Then hook your capacitor across those points.. Use a capacitor with a voltage rating of 35 volts or more.. 

BulletBob


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## supagav (Feb 8, 2008)

Thanks, 

I'll have a look into it. Have sent them off an email today. 

All the best, 
Gavin


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## rwbrashear (Jan 5, 2008)

Hello Gavin and Bob- 

You can build your own capacitor circuit. 

Here are a few notes regarding the circuit: 

1. Bob gives good guidance regarding the capacitor size. In general, the bigger the capacitor, the better the performance. Remember, larger capacitors require longer charging times. 

2. You will need to install a current limiting resistor to limit the "in rush" charging current for the capacitor. To allow the capacitor to bypass the resistor when dumping current back into the decoder, use a diode. (See the attached schematic.) 

http://1stclass.mylargescale.com/rwbrashear/DCC/Decoder_Capacitor_062408.JPG 

The RC time constant dicates the charging time for the capacitor. In other words, the smaller the resistor (or capacitor) value, the quicker the charging time. The capacitor is 95% charged after three RC time constants. Since the discharge bypasses the resistor, the decoder impedance (a function of the total decoder load, including the processor, motors, lights, etc.) will determine how long the capacitor can supply power. The capacitor will discharge over 60% of its charge in one RC time constant time period. 

3. If you have trouble programming the decoder, add a SPST switch to disconnect the capacitor from the decoder. 

4. If you call NCE, ask to speak with Jim Scorse. He can tell you where to find the GROUND terminal on the decoder. You should be able to use the V+ (blue wire) for the positive voltage. 

Good luck! 

Best regards, 
Bob


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## supagav (Feb 8, 2008)

Thanks for your reply! 

I've been pretty busy with work at the moment so I've barely had any time to look into it sadly. /DesktopModules/NTForums/themes/mls/emoticons/sad.gif Though I've got a holiday booked in this weekend which is going to be dedicated to just trains as we've got an open house on Sunday, so I'm hoplefully going to have some time to try it out. Thanks again, and I'll let you know how I get on. 

All the best, 
Gavin


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## Guest (Jun 29, 2008)

big capacitors can work BUT they come with liabilities. 

The biggest is that capacitors like to recharge quickly, resulting in current surges and possible pitting of the loco's wheels due to the high current surges. I did something similar to a small loco but I eventually converted the loco to RC/battery 

file:///Users/george/georges_stuff/web_stuff/girr.org%20pages/girr/tips/tips5/dcc_tips.html#dirt 

- gws


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## supagav (Feb 8, 2008)

Thanks for your reply George, 

I read your section on "DCC vs Dirty Track" on your website, very interesting thanks! I often use your site as DCC resource. 

When we wired our outdoor layout, I ran a track bus round the whole line with feeds every metre or so. Combined with Hillman railclamps, we have no real voltage drop of less than approx 0.2V or 0.3V. The track is usually kept very clean. The problem arises when the smaller locos such as the 44 tonner cross one of the LGB points it stalls on the dead frogs. I'm only looking to use a small cap with enough juice to briefly help it acrosss when I'm switching at very low speeds with Kadees. What size of Cap would you recommend? Would you recommend against this idea completely? 

The loco has all LED lighting and no smoke unit, although it does have a P5 sound unit installed so I'm not sure what the kind of current it draws. It runs exceptionally smoothly and apart from this small problem, the DCC conversion has improved its slow running ability. 

Thanks for any help or advice you can give me. 
All the best, 
Gavin


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