Lionel Lift Bridge 6-12782 Help!

If that was a radio hooked to an antenna, I'd say you took a lighting induced surge that burned up that copper trace, maybe arching to the screw next to it.  I can't help, but since there is no part ID silk screened at that spot and to you it appears that is should be soldered from one side of the board to the other, go for it, but usually that is not the only place a common connection would be made.  Follow the traces on both sides and see if there are other places that are connected from one side to the other.  A comment from someone who has a similar bridge apart would be best though.  My Lionel mechanical bridge is a #313 Bascule bridge full of motor and relays.

I know what caused it, I don't know how to fix it or if it can be fixed.

The cause is simple- as designed and per the manual, they are routing track power- that's right high current track power through the wiring and the circuit board back down to the track. They do this so the relays can cut power to the isolated segment so you don't run your train off a cliff of an open bridge. In doing so- with NO FUSES- they created a weak point and with a short- he blew this sky high in a smoke show.

There are no parts available for this bridge.

There are no schematics or wiring diagrams (internally) of this bridge.

There is no tech support for this bridge.

In a nutshell, again, what happened is you take this fragile older designed bridge, you make a mistake in the wiring, you use a powerful transformer with no fuses or circuit breaker protection and it smokes the boards right out of it.

I'm sorry this is the answer- but that's exactly what happened.

Previous answer on the topic of this bridge

@Moonman posted:

Here is the thread on the control box - there are no schematics anywhere for this bridge

Here is a general search results - check out the 6-12782 posts

Nice bridge when it works - subbed out by Lionel - all of the manf data is lost -

The manual https://www.lionelsupport.com/...ents/71-2782-250.pdf

I stress again, if you get the wiring wrong, there are no fuses, no circuit breakers- only smoke.

They are basically having you feed your track loop from the control box. If you had existing power drops and miswire this or have a simple derailment, this is exactly how you destroy this bridge.

Is this the lift bridge that had a sound board or chip upgrade that was required for either operation or sounds?

Not to my knowledge. I do know, the sound chip does not in any way control motion. It's nothing more than a preprogrammed sound chip with bell and horn- no more, no less- think like a diesel williams board.

The actual logic of this is all just a ton of discrete transistors on some of the most fragile boards I have ever seen in my life. The traces are terrible on these- super thin and thin copper. Just changing one component (like a transistor or capacitor) can be an utter disaster (because the insanely thin trace just rips to nothing left) resulting you you reverse engineering where that trace went and then bridging with a wire. You couldn't pay me enough to ever even look at one of these again. Worse than me hating on a Lionmaster repair. Again, if you know- you know.

Zak, it looks like the board mounting screw worked its way loose and rested against Resistor (R22) and shorted it out.  You see the remnants of what used to be R22.  Your board looks repairable.  The hard part will be to find out the rating for R22 since there are no know schematics for this that I am aware of.   

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Thanks for the replies fellas!

Upon some further investigation, I found that a sub-standard screw (flat head, wood screw) was used to hold down the board in that area.

Did this this make a temporary connection for the bridge to operate ??? The bridge did indeed operate with the burn marks.

Looking at the bottom of the board, I followed the trace to pin #7 (larger green wire on ribbon cable) it then goes across to the other tower board, then through that board (changing to pink) then goes down from there. [more investigation needed]

On the top side the trace goes through R22 then turns and goes between R21 and R22 on its way to a relay.

Please! If anyone has this bridge, could you take off the top of the tower (just pry open) and snap a pic of the main board ?

[The main board is located in the tower with the gray ribbon cable going to it]

Took apart a bridge to show the path.

#1 the mounting screw had NOTHING do do with the trace burning or causing the short. Absolutely nothing. They used self tapping screws for the plastic insulated mounting post- that was the factory screw- not something someone replaced incorrectly. So the entire discussion and assessment surrounding the screw being the cause of the short is just chasing nothing. The screw did not and could not short to anything.

#2 the trace is a through hole via- to go from one side of the PCB to the other. And as expected- it's related to the relays and the track power control system

#3 the trace has nothing do do with the nearby resistors in any way other than running nearby them, it is not electrically connected in any way. Tested with a meter

Again, your board burned at the through hole via between the bottom side trace to a trace on the top side.

There was no electrical component there, it was a copper tube- that again just connected from bottom side to top side.

That trace did not and does not connect to any of the nearby resistors of the burn mark.

Simply solder a wire between these 2 locations (the Yellow line is the most direct path- the blue line represents the original traces path). The red square outlines are showing the outlines of the relays on the other side of the board.

You got to give it to @Vernon Barry for taking apart a bridge and pulling the circuit board in question.  Thanks also for correcting my mistaken diagnosis.  The jumper wire should get Zak up and going but I have to wonder what would make a through board connection that hot.  Only if it was a high resistance solder joint could I see that happening.  

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Thank You Mr. Barry!

I now have a better under standing of the board.

I did talk to the previous owner and he admitted he put a different screw into the burned aera to "bridge the gap" so the bridge would work.

Is this why it worked after the 'Fire' ????

More questions for you all;

Would it be wise to put in an in-line fuse in that area? I would hate to have a repeat, or worse situation!                                                                                   If this trace on the board is for the 'sensor', Then wouldn't  the motor still operate ??

I re-read the posts here and I think some more investigation is warranted.

Over current protection of some kind sounds like a good start, maybe a PTC.  The unknown is how much current is too much for the wires and small PCB traces @Vernon Barry has pointed out?

Vernon also noted that this accessory had track power running through it in order to stop a train when the bridge is up.  In addition to adding a fuse/breaker of a TBD value, IMO it would be wise to create a small isolated power block extending only far enough on both sides of the bridge to stop a train at full speed before it reaches the drop-off.  This would avoid having either the entire layout's or a large power district's current from passing through the bridge. Or in other words, reduce the total current flowing through the bridge.  Otherwise, an appropriate fuse/PTC/breaker may keep blowing/tripping under normal operations.

Vernon, would you venture a guess as to what value fuse, PTC or breaker to use?

Sadly, I would venture at no more than maybe 5A. Flat out, the traces are just garbage thin on those circuit boards and don't forget- same manufacturing is the PCB down in the control box.

One day with spare time and have to go back and take pictures, but the club bridge, I had to do so many things. #1 we are not running track power through the bridge controller as originally intended. We are not isolating the tracks connecting to the bridge with the insulating pins- instead all three are solid pins. We disabled- and this is the part i don't remember the exact how on what we did , I just now it required moving some wire connection points under the bridge end sections to disable the train sensing. Last, in parallel to the bridge the tracks are bonded with no less than #12 wire to ensure in the event of a derailment or short, no current is passing from one side of the bridge to the other. This is especially true in a bridge up situation. Again, the idea was to isolate and augment in parallel the bridge electrically from one end to the other just like it was a piece of track with extra bonded together feeder wires. That way the electronics are still connected but not actually handling any track power and cannot control the leader tracks at either end. This means we must manually interlock so nobody can run off the track if the bridge is up. In fact, the bridge controller is not plugged in 99.99999 percent of the time and we only operate the bridge on the rare special occasion to hopefully not break it.

Hands down, even with all my knowledge, this is the most difficult, most complicated set of boards for a bridge I know of. There could be a dozen reasons why it's not working.

Could be one of the up or down optical flags is not in position at either end of the bridge- that's 4 potential spots for an error.

Could be the train sensing section- when you burned the trace, now that circuit cannot detect state.

I insist again, without even seeing it, there is NO WAY the screw had anything do with this. Even a big fat washer- there is no 2 points on the circuit board it was bridging in this location. It is a through hole via from one side of the board to the other just so that trace can route around the other components.

I'm not trying to not help, but at the same time, it's hugely impractical to fix this bridge. Shipping alone, no parts, and even touching the circuit board, you touch one solder joint and the trace just self destructs with heat. This is the impossible to fix bridge for all intensive purposes.

Again, figuring out what sensor is not in position, what error if there is an error on the circuit board, then when trying to fix one error not create 10 more in the process.

I would fix the trace by soldering a bypass wire. I know that should repair the visible damage we know about and is minimal risk of causing more trace problems. Beyond that, if it doesn't work, it's finding another bridge that does.

This topic has been a nice little warning notice for me. I've had this same bridge for awhile bought from a fellow forum member, and have always liked it, but reading all this made me want to treat mine with a little more TLC. This bridge is going on almost 35 years old, so it pays to know all its quirks and possibilities for killing its innards...

I've never hooked up the controller to track power - only through its own power supply - but have hooked up to insulated blocks on each side to the sensors terminals at the bottom of each tower. I'll definitely keep it unplugged unless I really plan to use it.

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WOW! Vernon, Yikes!

Well, that being said, here is where I'm at.

I repaired the Main board as instructed. I have power to the controller and the bridge. horn works, Bridge does not move.

The bridge indicator lights work as well as the tower lights and strobe. No power at the motor!

I have never used track sensors (don't have any either) or track power. I have approximately 36" of track on either side of bridge that will be controlled by a BPC and CAB-2

My next move is to remove it from the layout and do a deep dive into those aforementioned sensors. I know, call me nuts, but its worth it to me to tinker with it. Maybe I'll get lucky or maybe I'll just do a work around!

We shall see!

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Here are some of my findings; In regards to the aforementioned bridge (which you may or may not know)

W/O power, There is No continuity between the rails! Any continuity between the outside rails will result in the bridge Not moving! An isolated, outside rail, (rail closet to the ribbon cable) approach on either side will prevent movement.

The bridge center rail is electrically connected to the 'lock-on' labeled screw terminals on either side of the bridge. If track power is connected to the controller, when raised, power will be shut off to the screw terminals and any subsequent track block.

Using of the so called 'sensors' can and will result in the bridges main board being shorted, burned! Possible Fire Hazard!

>> Some Tid-bits: Towers are 8" x 4" and stand 21" high with a red, screw in base, E5 (5mm) bulb on top.

>> Bridge entry/exit has a 6" clearance from track. When raised, there is a 7" clearance from bridge deck to tower bottom.

>> The infamous, Nylon Gear!  Specs: Nylon gear is press fit on a 3 mm shaft. It has a diameter of 13 mm x 10 mm wide including teeth.                                   There are 20 teeth with a depth of 1.5 mm each.

In conclusion; I think it is a nice looking, well designed bridge over all. That said, it has over thought out electronic controls and poor execution!                Even given this is 1990's tech, made at a low price point, I still think certain things could have been built more robust and less complicated. So if you do have one of these antiques, enjoy it, but treat it as such!

To add to what @ZAK has warned about:

I have read in the past that the main red power on switch on the controller is not of the best quality.

I power my bridge from an old Z transformer. I used to keep the bridge controller red power switch on all the time, and just plugged the Z in/out of the wall. Once, when I plugged the Z in, the bridge raised about an inch, and I couldn't move it. I finally got it back down, but I don't remember how. So now I keep the bridge main power switch off during powering the Z on/off by plugging it into the wall. This may have a "my bridge only" situation.