Diodes

[1956Porsche]

I have a couple of older N scale Digitrax decoders that have blown bridge diodes and I'm looking to order replacements.  They are 0805 SMD and have an A4 marking.  I'm guessing they're 20 volts and 1 amp.

[Point353]

I have a couple of older N scale Digitrax decoders that have blown bridge diodes and I'm looking to order replacements.  They are 0805 SMD and have an A4 marking.  I'm guessing they're 20 volts and 1 amp.

Perhaps, more likely, a 40 volt (and 1 amp) rating.

http://www.zowie.com.tw/UserFiles/File/MSCD102H~MSCD106H(5).pdf

http://www.zowie.com.tw/UserFiles/File/AUMSCD102H~AUMSCD106H.pdf

[peteski]

I would also imagine them rated for more than 20 Volts.  40 V sounds more reasonable. Also, usually Shottky barier rectifier diodes are used (for their lower forward voltage drop).

When looking for replacement, their packaging also doesn't use standard SMD size nomenclature (like 0805).  You should be able to find a suitable replacement at Digikey or Mouser Electronics (those are usually my go-to sources of electronic components).

I'm worried that if those diodes (just one or all) are blown, other components on the decoder can also be damaged.  Diodes just don't usually blow up spontaneously.

[1956Porsche]

Thanks for getting back to me.  The information provided is what I was looking for.  I did have a few older decoders that I could cannibalize the A4 diodes from and fix a couple of decoders.  I also was looking for the data sheet and replacements.

Thanks again,
Joe

[peteski]

While the earlier advice is still valid, I did some more digging.
I went to https://smd.yooneed.one and looked up "A4"  https://smd.yooneed.one/code4134.html.

I suspect that MSCD104 Zowie Technology 0805 Diode SBR, 40V, 1A, Vf<0.5V(1A) is likely a match to what Digitrax uses.
It also shows that the standard SMD size nomenclature (0805) is used for certain diodes (new one on me).
Before you ask what SBR is, here is the answer: https://www.diodes.com/products/discrete/diodes-and-rectifiers/rectifiers/performance-sbr/

[1956Porsche]

Thanks for the additional follow-up and information.  The two decoders that I replaced diodes on are working great.   Will order a few replacement diodes and let you know how they worked out if you're interested.

Thanks again,

Joe

[peteski]

Thanks for the additional follow-up and information.  The two decoders that I replaced diodes on are working great.   Will order a few replacement diodes and let you know how they worked out if you're interested.

Thanks again,

Joe

Glad it worked out Joe, and yes please update this thread with any additional info you have later.