TMCC power board issue - K-Line K-28841

Get a closer look at the board that powers the fan unit. If it has a regulator on it you can tell what voltage the fan motor runs at. Optionally measure the voltage on the fan motor that works. Easy to make another regulator board or use one of those buck/boost board off the internet.

Pete

@Norton posted:

Get a closer look at the board that powers the fan unit. If it has a regulator on it you can tell what voltage the fan motor runs at. Optionally measure the voltage on the fan motor that works. Easy to make another regulator board or use one of those buck/boost board off the internet.

Pete

This is what's on the Fan Motor PCB:

To be brutally honest I would not know a regulator from a schmegulator but I'll extract the motor from the mount it's in and see if I can read any voltage info from that. Fortunately I do know about buck/boost boards and have some spare adjustable voltage AC-DC converters small enough to fit in the body shell. I think you are saying use that to power the fan from track power, right? It doesn't matter to me if the fans spin whenever there is power to the track (although I had wondered about wiring them to one of the can motors so they only operate when the engine is moving).

Can you read what is on those black devices to the right and foreground in your picture? 

Pete

@Norton posted:

Can you read what is on those black devices to the right and foreground in your picture? 

Pete

Two of them have this printed on them: 2N 3904 - 006. The third to the left appears to have this: 7 MPS A14. That one is in the space marked on the board as Q3; the others are are in spaces Q1 and Q2. 

I assume that this is some kind of constant voltage board. Possibly dumb question but what happens if I connect this to track power?

P.S. Motor is a Mabuchi but no serial number or other ID on it:

If the white coonector goes to the motor which I think it does then you should be able to connect to two black wires to a transformer, then monitor the voltage at the two pins in the white connector. That will verify if the board is bad or the motor is stuck, not uncommon. If you get nothing from the white connector then you will want to measure the voltage on the other board that works to determine what to use as a replacement.

Pete

Do NOT connect the motor to track power.  Since there is no smoke, I'd control the fans with the smoke output.  A simple DC power supply there will do the trick.  I'd probably use a variable power supply so you could adjust the speed of the fans.

No one suggested connecting the motor to track power. Relax John, late to the party again.

Pete

@gunrunnerjohn posted:

Do NOT connect the motor to track power.  Since there is no smoke, I'd control the fans with the smoke output.  A simple DC power supply there will do the trick.  I'd probably use a variable power supply so you could adjust the speed of the fans.

John, meanwhile I have sent you an email on variable voltage AC-DC power supply boards you've supplied for me in the past. 

I'll have to hunt around for the smoke supply on the control boards but I think the problem is that there's no power coming from that source in the front unit, for whatever reason. (I haven't tried toggling the TMCC smoke control on/off but will do so.) I think I have worked out that the motor is only a 3VDC model. 

It may be that the supply is already running on the smoke output, so turning on smoke would be a good first step in seeing if the supply is working.

It looks like they went overboard with the power supply design, a lot of parts for a simple power supply!

I am guessing they didn't use a common three terminal regulator is because they run that motor below 5 volts though they could have used another type of adjustible three terminal regulator. The roof fans turn at very slow speed even with the reduction provided by the pulleys. If we knew what the voltage coming out of that board is we could better provide options. 5v from the smoke fan may be too high or they could have used a 24 volt motor driven at 5v???

Pete

I'll report when I know more, after testing various options. It all looks like a contraption, but this time not of my own incompetent making. 

@Norton posted:

I am guessing they didn't use a common three terminal regulator is because they run that motor below 5 volts though they could have used another type of adjustible three terminal regulator. The roof fans turn at very slow speed even with the reduction provided by the pulleys. If we knew what the voltage coming out of that board is we could better provide options. 5v from the smoke fan may be too high or they could have used a 24 volt motor driven at 5v???

Well, since it's a 3V motor, I suspect around 3V.    I wonder how much current it draws...

@Hancock52 posted:

 I think I have worked out that the motor is only a 3VDC model. 

If it is in fact a 3 volt motor and they were driving it with 3 volts the engine would take off like a helicopter. Again, the fans don't turn that fast. I have one of these engines but hoping the OP can check the board voltage himself.

Pete

Trying to turn these motors slowly with any load normally results in very unreliable operation.  They have no torque if they're running really slowly.

This is true and the first thing to check is to make sure there are no wires dragging on the belts. This is actually more likely than either the board or motor being bad.

Pete

Right, many thanks to both Pete and John for the insights. The good news is that the fan motor and the MDK-039 PCB it's directly attached to are both functional. The fault, whatever the cause, is that there's no power from the connection at the white board near the motherboard. I tried Pete's test powering the lead unit PCB from the transformer and that runs the fans.

Power output at both the lead and trailing units' PCBs measures slightly more than 4 VDC and the fans don't spin at breakneck speed. Toggling the smoke unit on/off keys (and a soft reset) has no effect on either unit although it makes sense to me as John suggested that the smoke outputs would have been repurposed for the fan motors. I have not tracked down K-Line diesel reset codes so I have not tried doing that. P.S. Even with a Legacy command base connected, the fan speed varies with transformer lever movement so I guess that it might not be command controlled at all. 

So, as the PCBs appear to be OK, and unless this might cause another issue, I'll wire the lead unit PCB to track power. I really don't know how the PCB is feeding DC to the fan motor as there's no rectifier on that board (but there are several diodes on it, which I'm guessing have the same purpose). 

Just as a matter of interest, opening up the trailing unit shows a set of electronics that I don't think I seen before (but I am no expert), especially the big blue caps. There is a tether between the units so I guess that this is a slave board arrangement of some kind:

Many thanks again.

Pretty sure the roof fans just go to track power, they are not controlled remotely. There might be switch to turn them off but not sure of that. My E8 is buried right now. The E8 motors are all driven by a single motor driver in the lead engine. I think the caps are there just to smooth out the power to the trailing engine.

I ended up putting a Cruise M in each engine driven by a single R2LC. Required new tethers though for the added wires required.

Pete

I'd be tempted to run them on the smoke output, but you can break out the meter and see where the wires go for the input power to the board.

Yes, the four diodes on that board are obviously a full-wave bridge to rectify track power.