Problem with an electronic train controler.

[redneckalbertan]

I have a little Maxitrack 7 1/2" gauge locomotive that I bought last year not running and put a 24 volt VTX 75 board from 4QD late summer 2012. I had it out last year with the family for a trial run and She worked pretty good and was lots of fun.

Long story short, the club I am a member at is having their annual frost bite run on Monday the 18th this month. http://www.ironhorsepark.net/ Today I decided to make sure the engine was up and running after sitting for the winter and make a few adjustment for the first run of the year. While working I shorted 12V across two points on the board and there were some sparks and all the magic smoke from one section of the board escaped. I have enclosed photos of the board in question showing the damage. I don't know a whole lot about electronics, just enough to get me into trouble, but I think that the only damage to the board is shown in pictures 'a' and 'b' that I have enclosed. Pictures 'a' and 'b' have the damage circled in red and the two points that I shorted across are circled in blue. It is just the one 'wire?' that I believe was damaged. I can see no other damage and checking the circuit board on the back side there is continuity (checked with a multimeter) where the 'wires?' run in the circuit board on either side of the damage.

My proposed solution is to simply run a short piece of wire connecting the two points on the back of the board, that I have arrows pointing at in pictures 'c' and 'd', and solder it in place. (These two points are where the 'wire?' from the top side starts and stops and I can see no other deviation of that wire on the top side.) The questions that I have for you are as follows: Is there any reason why my proposal would not work, assuming that is the only damage done and given the limited amount of knowledge that you have of the situation? What gauge of wire should a person use? Does the wire have to be anything special like resistance wire or have any special properties or will copper wire work? It appears that there was some sort of varnish or other coating is on top of the 'wires?'. With that being burnt off is there any chance that weather/humidity will damage the board or is there a way that I can repair that or do I need to?

I do realize that there may be other damage done to the board and it may be garbage, but I am hoping that I can easily fix this and get my train up and running again.

Thanks for your help,
Andrew

[OddDuck]

Not having a schematic and pinout diagram to go by I would say no. You may have shorted across the power transistors and either fried them or some of the other chips on the back of the board. Your best, cheapest, and probably safest solution is to get a replacement board.

[steamin10]

From what I see, you have burned the circuit wiring loose from the board by the terminals, as they are raised and twisted off the board and obviously open. What is not obvious is testing with an analogue meter can load small circuit parts and harm them, while you get false readings, from another path. Use digital meters. Such is electronics.

You have nothing to lose here, from my outlook. Bridge around the burnt traces, using smallish wire from the auto store, or Radio Outhouse, and do what you can. You may get lucky, or not, but will hone skills you may not know you have. If you loose the whole shebang, you are no worse off, but may gain some understanding about the sections of control and power handling of that board, that will generally apply to all general electronics, with sense, decide, change state, and apply power, type controllers.

It looks like you lost the output leads from the power side. Power side electronics can usually stand a serious hit, and may open before burnout. Give it a try, no guarentees.

I dont have one of the 4qd boards, so it is just a SWAG on my part.

Traces that are exposed, if the board will work can be coated with clear nail polish, such as hard as nails, which is pretty strong stuff. (I keep some around to cover scratchs in automotive paint and rub it out.) It will not only protect but glue down a loose trace.

[David_T]

I have work in electronics for most of my adult life, so I finally have a little bit of experience. It does look like you just fried the trace on the top of the board. HOWEVER, there is one spot on the bottom that I do not like the looks of it. Between what looks like the number 120 and the M- symbol there is a bad looking solder joint and possible more burnt trace. If it is ok, then go ahead and replace the big burnt trace with a 22ga wire. As already said, nothing to lose at this point. Clear polish on your soldering for protection. Now much to worry about on the burnt side. Clean off the loose pieces and put polish on any exposed copper. Use your 40watt soldering iron, of course. (something small not the 150w Weller)

[DianneB]

Looks like that trace is burned back by the heat sink as well.

Nothing wring with replacing the trace with a piece of wire.

[hammermill]

as long as the trace repair is equivalent or larger to what was already there. there is hope . good luck

[cp4449]

If you have to get a new board, get one that is inside a box with the leads coming out. this helps with shorting out the boards. They do have a guy in Berkley CA who repairs boards. He can be found on their website.

I am trying to fix a 2002 board, with no luck.

[redneckalbertan]

Thanks to all who put their 2 cents in. Input from others who may have been in similar situations or have worked with electronics is always good when a person doesn't know a whole lot.

What is not obvious is testing with an analogue meter can load small circuit parts and harm them, while you get false readings, from another path. Use digital meters. Such is electronics.

I did not know that but a digital multimeter is what I have and used.

HOWEVER, there is one spot on the bottom that I do not like the looks of it. Between what looks like the number 120 and the M- symbol there is a bad looking solder joint and possible more burnt trace.

I think I remember that there from when I got the board and to me looks like a cold solder joint.

If you have to get a new board, get one that is inside a box with the leads coming out. this helps with shorting out the boards. They do have a guy in Berkley CA who repairs boards.

I did think about getting one of their controllers in a box, but decided that the $30 differance was better spent elsewhere... If I were to buy another one, well, that $30 sounds like a good insurance policy for an idiot who shut off the main breaker but forgot to remove the battery leads... I may however look into putting it into a box now.

[steamin10]

A coupla wraps of electrical tape, or even (ugh!) a wind of duct tape will accomplish the same thing for virtually no money. Ya , ok, I know I'm cheap. I revel in my economy. Even when a dime holds up a dollar sometimes. Its a hobby for catsake and really has to fit an awkward budget.

[WJH]

From my experience with Mosfets, it does not take much to fry them. Do the trace repair as others have stated, and I suspect you most likely will need to replace a couple of transistors.
The hard part to fix in any of this is if you fried a microprocessor, simply because there is only one source for the hex code and that is the engineer of the board.
Everything thing else is replaceable, just get yourself a good hot air rework station. If you need help removing components, I have one, I can do it for you, or you can go over to
http://www.sparkfun.com and buy one for around 100$

[redneckalbertan]

Well, I've been putting off trying to fix this for over a year now, I had some time off, was bored, and couldn't think of anymore excuses. I broke out the soldering iron solder and said, 'let's go!' Replaced the trace with a piece of wire and plugged her in. Turned the knob and nothing... Then I remembered I put an on off switch on my control box which is as of yet unlabeled turned it on turned the knob and off she went!

Thanks again to those who offered their advice and suggestions! I guess I got lucky and didn't do any other damage to the board.

[hammermill]

Good to hear of a positive outcome after letting it season for a while