ERR Cruise Commander mosfets and bridge rectifier get hot

Top suspect is one side of the motor is shorted to frame ground, that will take out the drivers in a flash!  It's frequently possible to replace the drivers on these boards and revive them, it all depends on what happened to it.

It's still getting hot as at least one of the FET drivers is shorted.

A couple years ago the first ERR CC that I installed I forgot to remove the Caps on the motor.  I discovered the mistake before I caused permanent damage. During the test I was running light and slow and feeling the FET drivers every lap of my test track and one was getting much hotter than the others. I shut it down and referred to the manual, sure enough it said NO CAPS on the motors. Problem solved.  Hope your solution is that simple.          j

@JohnActon posted:

Hope your solution is that simple.   

Probably too late for that John, it's getting hot not connected to anything.   That's an almost sure sign that one or more FET's have bit the dust and are shorted.

@BeefyT posted:

I have an ERR CC that I had put in another engine last year and I was installing it into another engine.  Last I had checked it worked fine.  I installed it in the new engine and at first when I applied power the engine just took off.  After about 2 times of doing that (while trying to isolate if there was a bad connection) it stopped and now the mosfets and bridge rectifier get hot and the breaker on my power supply trips.  I have absolutely no indication as to why this might have happened other than I may have an issue with the pittman motor in my loco.  Even now, when I unhook the motor 1 and motor 2 connections, the CC still gets hot but I don't see smoke or smell burning.  Do you think the board may have gone bad?  And if so, why?  I'm all out of ideas and I loathe the idea of purchasing another one.

-Tony

screw that goes into heat sink perm to long hitting circuit board!

https://ogrforum.com/...7#158815187549421527

I thought maybe that happened as well.  When I replace the mosfets I'll double check for clearance.  Thanks!

https://ogrforum.com/...5#158815187548383665

John,

I've ordered some replacement mosfets and I'll report back one I repair them.  Hopefully that is the issue.  I may have caused the issue myself (thinking about what you said about the chassis ground...that makes the most sense) since it is an MTH locomotive I was reusing the 10 pin pcb and I think I might have dripped solder across the connections...grounding out the engine leads.  I did test all of the pins for continuity but maybe I missed something.  Regardless, I have another pcb that is clean that I'm going to try out...the old one had a short anyways.  I should have swapped it from the get-go.  Good grief.

-Tony

@gunrunnerjohn posted:

Probably too late for that John, it's getting hot not connected to anything.   That's an almost sure sign that one or more FET's have bit the dust and are shorted.

Pardon...I'm new to posting here.  I didn't respond correctly in my previous post.  What I previously said:

I've ordered some replacement mosfets and I'll report back one I repair them.  Hopefully that is the issue.  I may have caused the issue myself (thinking about what you said about the chassis ground...that makes the most sense) since it is an MTH locomotive I was reusing the 10 pin pcb and I think I might have dripped solder across the connections...grounding out the engine leads.  I did test all of the pins for continuity but maybe I missed something.  Regardless, I have another pcb that is clean that I'm going to try out...the old one had a short anyways.  I should have swapped it from the get-go.

-Tony

@BeefyT posted:

Pardon...I'm new to posting here.  I didn't respond correctly in my previous post.  What I previously said:

I was responding to a different poster that suggested a simple solution.

@gunrunnerjohn posted:

I was responding to a different poster that suggested a simple solution.

Oh, yeah, I knew that!  I wasn't trying to be ugly or anything.  I was just letting you know I received new mosfets and I'll let you know how it goes once I get them in!  I was originally trying to respond to one of your earlier replies and I messed it up.  Still learning this thing.  Thanks again.

-Tony

@gunrunnerjohn posted:

Top suspect is one side of the motor is shorted to frame ground, that will take out the drivers in a flash!  It's frequently possible to replace the drivers on these boards and revive them, it all depends on what happened to it.

It's still getting hot as at least one of the FET drivers is shorted.

So I replaced the FET drivers.  It still gets hot when in forward or reverse but everything responds again and it will shift from forward, neutral, and reverse; even the rail sounds board responds to it.  But when it’s put into a direction, the motor will try to turn (I tried a couple different motors with same result) and will show about 1/2 volt. Then after all that the breaker will trip.  So maybe bridge rectifier now?

Tony

Well, the bridge is certainly a suspect.  Also, if the bridge is bad, it will pretty quickly kill the FET drivers, so I'd investigate that before I moved on.

I'd also test this on the bench and see if something in the locomotive is drawing excessive current and causing the issues.

@gunrunnerjohn posted:

Well, the bridge is certainly a suspect.  Also, if the bridge is bad, it will pretty quickly kill the FET drivers, so I'd investigate that before I moved on.

I'd also test this on the bench and see if something in the locomotive is drawing excessive current and causing the issues.

So, do you have any idea how many volts should come off the bridge? It's basically coming right off the hot wire in, correct?  So if I've got 15-18 VAC coming off the rails, it should be about the same DC coming off the bridge?

-Tony

As an aside, what transformer are you using?  If it's a ZW, you are drawing some serious current to cause it to trip.  I don't think your replacement FET's would last long in that environment.  With the board removed, you could (on a test stand/condition) measure the current your motor draws with varying voltage hooked up to it.  Never having measured one on the newer DC "can" motors MTH used, I would still venture a guess that your motor should draw about 3 amperes at full throttle, and corresponding less at lower voltages.  So whatever you measured at full throttle, is the worst case load you should experience with a working ERR Cruise Commander.  Actually, the load with the CC at full throttle should measure a slight amount less than the directly hooked up motor.  Not a lot less, just a little.  There is negligible current loss due to the FET's.

@donhradio posted:

As an aside, what transformer are you using?  If it's a ZW, you are drawing some serious current to cause it to trip.  I don't think your replacement FET's would last long in that environment.  With the board removed, you could (on a test stand/condition) measure the current your motor draws with varying voltage hooked up to it.  Never having measured one on the newer DC "can" motors MTH used, I would still venture a guess that your motor should draw about 3 amperes at full throttle, and corresponding less at lower voltages.  So whatever you measured at full throttle, is the worst case load you should experience with a working ERR Cruise Commander.  Actually, the load with the CC at full throttle should measure a slight amount less than the directly hooked up motor.  Not a lot less, just a little.  There is negligible current loss due to the FET's.

For this (as I have it on my dining room table which my wife is not happy about) I'm just using an MTH Z-750.  It is an MTH loco with a Pittman motor but I've taken it all off the loco and I didn't test the current but the power out from the CC.  I was only getting about 1/2 volt coming out.  I think gunrunnerjohn was correct in that I might have shorted to the frame ground before and that's what started this mess.  It might be the motor but I tested it on another motor I have that I know is good and the same thing happened.  The motor would turn just a little bit and would spin if I assisted it but then the breaker would trip after a moment (and the board gets stinkin' hot).  I thought maybe the motor might have been the culprit in the beginning but now I don't think that is the problem as I tried it out on a separate motor and it behaved the exact same way.  I'll check the current draw from the motor tonight but you have any idea what would cause so little voltage to come out of the board when I'm supplying 15-18V off the transformer?

-Tony

Tony, to test your bridge and not fry anything, you should disconnect/unsolder the secondary or DC load. (+ and - tabs).  With no capacitor hooked up, the DC output voltage will approximate your AC input.  I would suggest using a 18 or 24 volt light bulb from and old switch if you have one around as a load for the bridge.  Then you can see the light bulb dim as you reduce the transformer input to the bridge voltage.  The lamp brilliance should somewhat follow the transformer voltage input to the bridge.  This isn't the greatest test for one of the bridge diodes being shorted, however.  If I was trying to test the bridge, I would have an electrolytic capacitor hooked up to the DC output terminals, and look at the waveform on an oscilloscope.

I am sure GRJ can suggest a better method to test the bridge.

Hi Tony, A shorted diode in the bridge could cause this, and would rather quickly fry your new FET's.  It is best if you can disconnect the bridge DC output, and see what it measures on a DC voltage scale on your multimeter.  If it only shows 1/2 volt DC or so, especially with your Z-750 cranked up, the bridge is almost certainly bad.

See if GRJ chimes in with a better way to test.  I have to get back into my train mode.  Normally, I restore OLD electronics, and have a variety of electronic instruments to help me out.  I am living in a less than 10" by 10" room, and am very challenged to work on anything, as all my belongings have to fit in the room.  I just received a NOS Lionel C&O Hudson (1995 vintage) that I am converting to a DC motor and a ERR CC commander to drive it with.  I have to send a fellow my Lionel Pulmore motor to have the gear? removed and put onto the new "Pittman" motor.  I work on the fold down part of a small antique desk!  My situation is comical!

I'm going to try to fit a loop of Fasttrack under the bed and sticking out on one side to run some new trains on.

@donhradio posted:

As an aside, what transformer are you using?  If it's a ZW, you are drawing some serious current to cause it to trip.  I don't think your replacement FET's would last long in that environment.  With the board removed, you could (on a test stand/condition) measure the current your motor draws with varying voltage hooked up to it.  Never having measured one on the newer DC "can" motors MTH used, I would still venture a guess that your motor should draw about 3 amperes at full throttle, and corresponding less at lower voltages.  So whatever you measured at full throttle, is the worst case load you should experience with a working ERR Cruise Commander.  Actually, the load with the CC at full throttle should measure a slight amount less than the directly hooked up motor.  Not a lot less, just a little.  There is negligible current loss due to the FET's.

Actually, 3 amps on a can motor that doesn't have a huge load is WAY too much!  I haven't seen any of them draw anything like that.

I have a Pittman 9433F686 12V motor here, and at 12VDC, it's drawing 180ma with no load.  A Mabachi RS-385SH clocks in at 120 ma, and the Mabachi RS-555 is running 240ma.