Help? I let the magic smoke out (Kato DE10 N)

[defor]

So, I was following along instructions for adapting the N scale Kato DE10 to DCC using DN163K1D, and apparently I didn't ground the inside of the clip wells enough, and after a few loops around my test track, I was getting stutters, and when I pressed on the pcb, it let out a large whiff of smoke as the component marked "506P" literally went up in smoke.

 

OOPS!

 

I compared the board to some of my other Digitrax decoders, and they all share the same "506" and "516" SMD chip combo, but for the life of me, I can't seem to track down what these parts are in any of the SMD codebooks online.

 

I've removed the chip off the board with my hot air rework station and cleaned the traces, and everything checks out- the DCC decoder also works otherwise as expected both on programming track, and for LED control on my main track, but without this chip, I have zero motor power.

 

Any idea what this part is? I assume it's some kind of voltage regulator but I'm really not sure!

 

Thanks!

 

[kvp]

I think that was a dual transistor ic, each forming half of the motor H bridge. What you had is a short between one of the motor outputs and apparently one of the track pickups as the outputs should be (in theory) protected against motor shorts. I looked at the Mouser catalog and at least a dozen companies make similar chips, but you need a matching set (high and low drivers) for the H bridge to work.

[defor]

Thanks kvp!

This actually sounds right-   -    that said, I reached out to Digitrax earlier today to see if they could provide me with any details about the circuit they're using, and apparently it's company policy not to provide any details, but they say that they do offer a repair service that I was actually unaware of- It's 17$, but admittedly, might be more worth it than attempting to duke it out with tracking down a replacement set of ic's. I already "oopsie!-ed" pretty hard here, so I'll probably just take the repair option.

 

I was also concerned about the "modifications" I had performed (aka removing the crispy chip), but apparently they were ok with the desoldering job I had done, and it was fine.

 

Kinda feels like a bit of a shame that the details of the hardware are a little "black box" in nature, but I guess it's an industry decision eh?

 

One way or another, I'll definitely be wary against shorting the outputs to the powered frame in the future (esp. as I have plans for a bunch of DE10's on my layout.

I simply under-insulated, and it cost me!

[Kiha66]

Actually, digritax repair/replacement is free for a year I believe, even for customer caused damage.  Just send it to them and they will fix it or send you a new one, you just pay for the shipping.  Look up their "no worry warranty".  I had a sound decoder fail and they replaced it even though it was most likely my fault it broke.  

http://www.digitrax.com/support/returns/

[kvp]

8 hours ago, defor said:

Kinda feels like a bit of a shame that the details of the hardware are a little "black box" in nature, but I guess it's an industry decision eh?

Actually not really. Digitrax chips are much more transparent than most european brands. For example they don't use special hardware or custom chips, just what is available off the shelf at the time. The central units are usually midrange Microchip PIC-s and all other components could be sourced from multiple manufacturers. It's also relatively easy to reverse engineer their boards. On a basic decoder, you'll find a full diode bridge, a low current voltage regulator, a motor driver and an auxiliary driver besides the general purpose microcontroller. Their most simple designs are actually the Kato decoders. Just look at the components of a single output internal light decoder. Digitrax is also a pretty nice company as they published their protocol specifications to allow 3rd party developers to make additions. The whole Fremo DCC standard sprung up around the homebrew copies of their components.

 

On the other hand, some european makers have dedicated custom chips doing all the work and these are in chip scale packages covered with the classic black glue blob. Those are totally unservicable and not worth the effort to reverse engineer. Also very hard and costy to update, so these decoders tend to remain as is for many years and lag behind in features. The worst offenders in this regard were the european SX decoders.

[defor]

 

3 hours ago, kvp said:

The central units are usually midrange Microchip PIC-s and all other components could be sourced from multiple manufacturers. It's also relatively easy to reverse engineer their boards.

I follow what you mean- I can't imagine that the PICs are left unlocked however such that they can be dumped...

 

Aha, 

10 hours ago, Kiha66 said:

Actually, digritax repair/replacement is free for a year I believe, even for customer caused damage.  Just send it to them and they will fix it or send you a new one, you just pay for the shipping.  Look up their "no worry warranty".  I had a sound decoder fail and they replaced it even though it was most likely my fault it broke.  

http://www.digitrax.com/support/returns/

Aha- you're right! seems that I didn't get to the "payment" section where "under warranty" is there!

I feel a bit silly even making this thread now!

[inobu]

Like kvp said its tied to the H Bridge

 

It might be a SOT23-6 N CHANNEL ENHANCEMENT MODE MOSFET

 

Inobu

 

 

[kvp]

3 hours ago, defor said:

I follow what you mean- I can't imagine that the PICs are left unlocked however such that they can be dumped...

That's not really needed as the register map and the detailed functionality is included in the programming guide. Most features that would be tricky is implemented by the hardware, so only relatively simple code is needed. And the open dcc community provides that. It's cheaper though to just buy the digitax decoders assembled and tested.