Author Topic: Digitrax cap issue  (Read 539 times)

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AKNscale

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Digitrax cap issue
« on: February 06, 2018, 09:54:36 PM »
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Ok, a little venting plus some technical questions. Here's the backstory:
A couple years ago I installed 6 sound decoders in a friend's group of SD70MACs(they were SDN144K1Es). They aren't a LOKsound, but they're effective. However, they've had pickup issues from the start(They cut out, which being Digitrax means that they restart their entire sequence. Not so good for a 100 car coal train during the middle of a show.). They never really had a problem on DC.

Now:
I've come to the conclusion that the pickups are fine(they generally cut out in the same spots on the show layout). My thought is that maybe the caps aren't good enough, so I'd like to add better ones.(here's the rant) Today I decide to call Digitrax. They did tell me that the caps on those decoders are 25V 100uf caps. That's where the help stopped. I asked what voltage the caps actually run, and how much capacitance those decoders can handle, if 440uf would be safe? The answer was, " Those are engineering questions, and we do not answer engineering questions." He did also apologize, but it just erks me that I just want to make sure that I'm not going to burn up the decoder or caps when I improve the product's performance, and they won't even help me.... Matt from ESU was more than happy to help me when I've called....(rant over) I'm guessing that there's a reason, but it still erks me

The questions:
Ok, I'm guessing the caps run at track power(14-15V), but has anyone mapped this decoder out? @peteski
Has anyone upgraded the cap on these decoders?

peteski

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Re: Digitrax cap issue
« Reply #1 on: February 06, 2018, 11:13:21 PM »
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I stay away from Digitrax sound decoders.Even more so after I recently realized that you can't even re-map the function keys (like if you want to use a function key to turn on a strobe light).

I'm surprised about Digitrax's attitude.  That reminds me of a recent issue I assisted with. Friend of mine wanted to use the common-positive (blue) connection on a DZ126 6-pin decoder.  So he asked Digitrax where was the "blue" pad on the decoder, so he could solder a wire to it They told him that this decoder does not have that functionality.  Bullcrap!  the 6-pin version of DZ126 uses the identical PC board as the wired version (which does have the blue wire).  So I showed my friend where the "blue" pad was. So much for tech support.  :|

In my experience, decoders from all the manufacturers share very similar design for the power supply section.  It should be safe for you to replace the factory capacitor with a larger value one.  While I don't think it is needed for 400 uF, if you want to be safe, you could add the typical resistor-diode circuit in series with the cap to limit the inrush current.

Here is an example of how to wire the diode/resistor combo.
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AKNscale

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Re: Digitrax cap issue
« Reply #2 on: February 07, 2018, 03:59:23 AM »
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I agree wholeheartedly. Apparently I only did 5 for him, lol, and I bought 2 for both my SD50s and 2 for my GP38s. This was all before I found LOKsound. My first problem was the installs, especially on the GP. By that I mean that the sound wasn't good enough to me to justify the work/customizing to get them installed nicely(FYI, these are the 8bit, this was all well before Digitrax came out with their 16 bit decoders). Then I realized just how limited their sound library was. Finally, I found the Digitrax stall.... Other manufacturers don't have this problem as badly.

Yeah, it's sad because it may not sound like it, but I do like them. I just prefer ESU because they are much less limited across the board. The lack of support only makes it worse for Digitrax...

Thank you for that peteski. As always, excellent info!

Wolf N Works

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Re: Digitrax cap issue
« Reply #3 on: February 10, 2018, 07:29:19 AM »
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I replaced all of the Digitrax caps with two or three 220 caps and had no problems on the 4 pr 6 locks that I put them in