DanVW,
It's the same model. I have both the 256 and 269 GP 38-2. I ran the engine locked in forward and it ran fine for about a half hour. When I switched the e-unit to the on position is when I had problems. As soon as I hit the direction button or reduced the voltage to switch directions it would either stay in the same direction or not do anything. I just recently cleaned the track and I'm using an MTH Z1000. I took it off the track to see if the wheels were dirty but they were clean. Placed the engine on the track and turned the voltage up and it ran in forward. As soon as I hit the direction button it tripped. Know it will not run at all. The transformer trips all the time. Thanks for the response and yes I am willing to work on it if you can walk me through it. Greatly appreciate it.
FabbDadd,
The 1st and 3rd pics are of the audio board, so let’s disregard them for the moment. The last pic is of the roof fan driver board (if my memory serves me right) and not likely the issue.
First, you should isolate the audio board and roof fan driver board from the loco and retest just to make sure the symptoms remain. If they symptoms disappear, reconnect one board at a time to troubleshoot and isolate the problem board. ***Take pictures before you disconnect any wiring. If you run into trouble wiring things back up, you can go back to the photos later. Label like colored wires if needed.***
To me, it sounds like the 14 pin PIC failed based on your description of events. It’s clearly visible in the 2nd pic on the left side directly between your fingers mounted vertically on the motor driver board marked MC14013BCP.
The logic of this PIC chip is a flip-flopping action similar to a latching relay, but not entirely. The PIC chip is a low current/low voltage switch that controls the action of 2 transistors on the board. In turn, the transistors act as a slightly higher current/higher voltage switch which control the 6VDC relays. The circuit essentially takes a few current/voltage steps to switch the actions of the relays (2 large black boxes on the motor driver board labeled K1 & K2).
When you initially power up the AC track voltage, the loco should be in the FWD direction (1st relay is energized in the closed position which powers the forward direction of the loco).
•The first time you press the direction button, DC voltage switches the PIC to de-energize the 1st relay which opens the contacts and the loco rests in neutral.
•Press the direction button a 2nd time, the PIC energizes the 2nd relay into the closed position and the loco moves in reverse while leaving the 1st relay de-energized.
•Press the direction button a 3rd time, the 2nd relay returns to normally open and the loco rests in neutral.
•Press the direction button a 4th time, the PIC energizes the 1st relay again returning it to the closed position which then moves the loco fwd. The PIC functions as: 1-closed, 1-open, 2-closed, 2-open, repeat. 😮💨
Now, the question is, what happened to yours to cause the behavior you’re experiencing? The PIC has most likely failed and is allowing voltage to leak thru its #1 circuit so the forward relay (1st relay) never de-energizes. It’s like you’re closing both relays at once or trying to run the loco in both directions simultaneously when you press the direction button while the PIC tries to cycle. You’re getting opposite polarities converging at the outputs of both relays! The outputs of the relays are tied together at the motor connection. You can confirm this by removing the transistor labeled Q4. This should break the call in signal from the PIC to the 1st relay. You can then power it up and the loco should remain at rest on startup and 1st use of the direction button. Press the direction button a second time and it should move in reverse. There is a chance one of the transistors is at fault so I’d recommend replacing them along with the PIC. They’re cheap.
Here’s what I’d do: order a replacement PIC (MC14013BCP) and 2 transistors (labeled Q4 & Q5 on the PCB near the relays). All can be ordered on Mouser Electronics or Digi-Key. Hint: once you remove the components, use your phone’s zoom function to take a picture. It’s much easier to zoom in on an already enlarged picture to get the identification marks off of the hard to read parts. Using flush-cut side cutters, snip the pins at or near the pcb. Unsolder the pins and clear the PCB’s through-holes with desoldering wick or suction tool. Clean and prep the board. Install the new components using the least amount of heat possible and watch the excessive use of solder. ***Pay close attention to the orientation of the PIC on the PCB and reinstall the same way*** Reassemble and test.
Sorry for the long explanation. Let me know how it goes.
Thanks,
DanVW