JLC GG1 - Shorting out Help

Make sure that the rear truck is tracking properly.  I had a similar issue with mine until I changed the spring tension on the rear truck.

The engine never starts to move and I am testing on straight level track. I opened the engine and the r2lc looks good. The motor driver is another issue. On one of the four fets the plastic spacer is melted on. With my meter I am reading a short between the center pin and outside pin. The other 3 fets do not give any direct short readings.

There's your first problem!  You clearly have an issue with the motor driver, it's still available from Lionel.  Part #22 on the JLC GG1 Parts Listing.  I'd also check the wiring to make sure that something didn't get grounded to take out the motor driver, obviously the one driver got really hot!

I've looked at the wiring and so far all looks good.  I plan to re-check it all.  The engine was running fine on the layout, and just died suddenly while moving.  There was no derailment at the time.  The engine was moving at speed step 2 or 3 and just stopped and the transformer tripped.  Glad the ZW-L tripped quickly or more damage may have occurred.

Its funny that it will run in the other direction without issues.  If a wire was shorted I would expect it to blow the fets in both directions.  I was having a signal issue with the engine on one part of the layout.  The lights would flash a bit and the engine would stutter.  I've never seen a poor signal issue cause a driver board to blow.  Is that possible?  The engine was pulling a light load (6 modern freight cars).  Maybe a motor issue took out the driver?  The motors are running ok in the other direction.  Really puzzled as to why the fet blew.  Can a fet just die?

Is this Odyssey 1 worth replacing with a Cruise M? 

If it runs in the other direction, it probably just took out the DCDS.  You could take a stab at replacing that Triac, it's a BTA08-400BRG.  Truthfully, I'd probably replace all of them just to be safe.  Do note that you MUST have them insulated from the chassis or they will fry.

John, Don't you mean the FETs?  The one that melted the plastic insulator is IRF5210.  There are 2 of them on the board.  The other 2 FETs are IRF540.  I have more plastic insulators to replace the melted one so I could replace the FETs and see what happens.  The FETs have thermal pads behind them.  They appear undamaged.  Do I need to replace them?

cjack posted:

Is this Odyssey 1 worth replacing with a Cruise M? 

The FETs are $2 each and $1 each.  Total to replace all 4 FETs is $6 and change.  That's way cheaper than putting in a Cruise Commander.  If anything, I could just wait until Lionel's half price sale and pick up a new Odyssey Driver board for $45.  The cruise command would require rewiring.

Interesting, I just looked at an Odyssey I DCDS to see what it used, and it had the above mentioned Triacs.  Obviously there is more than one design of the DCDS out there.  Clearly, I'd use the type of driver part that is in your board.

So I replaced the b!own mosfet and reinstalled the board.  Tested the engine. Forward motion good.  Sounds, couplers all work.  Tried reverse. I saw a quick spark by the bridge rectifier which is tucked behind the figures. Then the same mosfet blew again. Magic smoke released. Took the board back out and the plastic insulator for the blown mosfet was melted. I also noticed the stand alone bridge rectifier that sparked was warm.

 Can something be taking out the driver board or is the driver board board just bad?

Yes, is it grounded to chassis or properly isolated?  Can be a current limit resistor that is shorted, or if they use a flashback diode it may be shorted or you can have internal trace in the board that was damaged and shorted.  Sometimes you have to replace the triac or fets in pairs.  Can be a lot of things.  G

The fets have thermal pads which insulate them from ground. I had installed new plastic spacers for the screws so they were insulated as well.  if something was shorted or blown wouldn't that take out the odyssey board when running in either direction? I can get the loc to run forward. It's only backward that causes a short. There is a bridge rectifier wired in between the odyssey sensor on the motor and the odyssey board. That is a gnu606. It has a wire connecting the positive and negative terminals together. One of the ac lines goes to the odyssey sensor. I think the other ac line goes to the board.  I could remove the bridge  rectifier and test it. I also have more fets. I could replace the pair on the board. First time I only replaced the one that read as shorted by my meter. The other 3 fets still read will no shorts so I assumed they were fine. I am thinking it may be just a board issue but not sure what I can do to confirm that. Can the radio board cause this problem? I had to replace the radio board last year as the original stopped detecting the command signal. I upgraded the board from version 11 to a version 13 r2lc. The only other hardware in the gg1 besides sound boards is the voltage regulator. But I thought that only affected the smoke unit.

I guess I could also disconnect the odyssey sensor and try the loc with odyssey turned off to see if still shorts with that off. Thoughts?

It's really hard to say what is going on without further diagnosis.  George is right, I normally replace the FET's or triacs in pairs when there's a failure.

Not necessarily.  The forward and reverse circuits are isolated.  So there can be a short or damage that only effects one direction.  G

As time allows, I will try replacing both fets this week and see what happens.  There is a separate bridge rectifier going between the odyssey sensor and the odyssey motor driver board.  I plan to pull that out and test it outside the circuit to see if that is causing an issue.  I will report back once I know more.

Once I replace the fets, is it possible to put the odyssey driver board in another loc to test it?  I have a TMCC M1-A (6-38056), Century club sharks (6-14532), and a TMCC K4 (6-38025) which all have odyssey.  The boards are a different flavor as they have different part numbers on Lionel's site.  If they are compatible, it would be a good test to see if the problem is the board or something else.

Thoughts?

It's possible, they will generally work, I believe all the different part numbers had to do with response curves, and how the aux outputs on the 10-pin connector were configured.

So I sent Mike Reagan an email and he confirmed I can try the odyssey board in any odyssey loc. So after replacing both fets on the board i tested it in another loc and it works! Both directions are working.

So the question now is, do I plug it  back into the gg1? I still dont know why the fets blew in the first place. The thermal pads look good which insulate the fets from ground. I'm thinking of pulling the motors out and testing them with a 9 volt battery to ensure both directions work. After that I think the only things to check are the radio board and the bridge rectifier.

Make SURE that the motor leads are not shorted to the frame.  You can test the motors together by connecting to the motor leads on the DCDS harness.  The R2LC has nothing to do with the DCDS smoking, it's not capable of causing that.  If the DCDS works in another locomotive, the bridge rectifier on it is obviously good.

You really want to measure the current the motors are drawing as well.