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Reminder about RF supressors

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  • Member since
    January 2005
  • 550 posts
Reminder about RF supressors
Posted by hdtvnut on Wednesday, August 27, 2008 5:18 PM

Ran into a case where I installed Digitrax DH123 decoders in Bachmann Acela engines.  They were working fine on my and my club's NCE systems, but on my second club's Digitrax system, were erratic and unusable.  It took me awhile to remember reading somewhere that the RF chokes on some lightboards (or beads on some wiring) can cause problems with DCC; when I jumpered the chokes, the engines ran fine.

Since many people know about this, I bring it up mainly because it is not mentioned in any of the DCC books out there, or in the Bachmann paperwork (WHAT paperwork?).  Also because the problem also seems related to the type of system, which can be confusing.

Regards

Hal

 

  • Member since
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  • From: Western, MA
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Posted by richg1998 on Wednesday, August 27, 2008 5:43 PM

I do not know what the PC board looks like, but usually there are two or three yellow capacitors to clip With the capacitors gone, the two inductors are not an issue. I have clipped the capacitors for two Spectrum locos and they run fine. I do not have any links but use Google to search for DCC cut capacitors. You will get some hits.

Rich 

If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

  • Member since
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  • From: Amish country Tenn.
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Posted by loathar on Wednesday, August 27, 2008 7:56 PM
 richg1998 wrote:

I do not know what the PC board looks like, but usually there are two or three yellow capacitors to clip With the capacitors gone, the two inductors are not an issue. I have clipped the capacitors for two Spectrum locos and they run fine. I do not have any links but use Google to search for DCC cut capacitors. You will get some hits.

Rich 

Yep. My NCE and MRC decoder instructions both said to clip the ceramic caps off or they would affect motor control and performance.

  • Member since
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  • From: Western, MA
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Posted by richg1998 on Wednesday, August 27, 2008 8:03 PM

I found a couple photos. The first one I removed the caps and inductors. I needed every bit of space.  I could have left the inductors.

The second is a PC board in a DCC ready loco. I clipped the surface mount capacitors using small flush cutters. The caps where C1, C2, C3. I removed the two inductors on the bottom side of the board as I again, needed all the space.

 Rich

If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

  • Member since
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  • From: Bedford, MA, USA
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Posted by MisterBeasley on Thursday, August 28, 2008 7:02 AM
People should be careful about removing capacitors.  It's important to understand what each of them does.  Not all capacitors are necessarily part of the RF suppression circuitry, and removing them could have unintended consequences.

It takes an iron man to play with a toy iron horse. 

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