What's the most likely failure component for a PS/1 unit that will only run in reverse? I'm thinking the relay or it's driver. The motors work fine in both directions, and when you attempt to go forward, the RPM ramps up like the engine is moving, but nothing happens. When you cycle back to reverse, it takes off like it should.
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I'm guessing you mean command mode. I think it's possible to lock a engine in a directional state even in command mode. might be wrong though, I would do a factory reset or check out the gears for some obstruction, iron filing what ever. Do the flywheels turn in both direction with out any binding?
No command mode on a PS/1 locomotive. 
What's the most likely failure component for a PS/2 unit that will only run in reverse? I'm thinking the relay or it's driver. The motors work fine in both directions, and when you attempt to go forward, the RPM ramps up like the engine is moving, but nothing happens. When you cycle back to reverse, it takes off like it should.
John,
Better check your question again. (PS2 unit)
John,
It could be one of the relays. There is two. One for forward and one for reverse on PS1 boards.
Right you are guys, I made the subject correct and screwed up in text! It's a PS/1. I fixed that error in the text.
Joe, my top suspect is a relay, but before I start replacing parts, I figured to ask what other folks experience has been. It could be the drivers that drive the relay, I'm sure they're not direct logic controlled relays from the look of them. I suspect there's a driver transistor, a likely suspect as well.
I suspect there's a driver transistor, a likely suspect as well.
Yes...I'd bet money on the transistor if I had any. Get'er fixed John.
I can't think of much else that could do this, the reverse unit for PS/1 seems a simple rig. I see two transistors close to the relays, time to see what they are...
The micro processor is shot and you need a new top board and the only guy that had them died, the scaled tin rail. Had to do a people search to find out as his web site is still up like it should be. Now only mth maybe can help other wise it garbage.
The micro processor is shot and you need a new top board and the only guy that had them died, the scaled tin rail. Had to do a people search to find out as his web site is still up like it should be. Now only mth maybe can help other wise it garbage.
Well, if it is the reverse relay causing the problem, it's on the bottom board and changing the top one will not fix the problem. I believe John will figure it out and get it fixed.
Also, I believe there's plenty of used PS1 boards available from engines that have been upgraded to PS2 so Scaled Tin & MTH isn't his last resort.
John, if you can wait until tomorrow I can give you a test procedure to manually test bottom without top board. Those transistors do energize the relay coil. You also can tap the relay with a screw driver to see if it is sticking. G
John, If you remove the top board and have the bottom board in front of you with Large Coil Capacitor to your left and relays to your right. The far left female connector of the 8 pin row is output of LM337 Regulator the next one to the right is the Base to the Rev relay, 3rd is 7905 VR output and 4th is FWD relay. The fifth is PCB Ground. I check voltages from pin 1 to 5, then 3 to five. Then if you jumper 1 to 2 the engine should run in reverse, and 3 to 4 in Fwd.
The transistors are PNP 2N5087. G
The micro processor is shot and you need a new top board and the only guy that had them died, the scaled tin rail. Had to do a people search to find out as his web site is still up like it should be. Now only mth maybe can help other wise it garbage.
Hard to imagine the audio board, which works perfectly, would cause the locomotive to only run in one direction. 
George, I did actually rap on both relays to see if I got any life out of them, no joy. I think I'll take a run at replacing the transistors, they look to be pretty generic specifications, I'm sure my junkbox has something close.
I think I'll take a run at replacing the transistors, they look to be pretty generic specifications, I'm sure my junkbox has something close.
John,
I have been following your post! Hang on! They are coming priority mail!
Good luck & Thanks,
I've got one on the bench that tries to run forward in all four positions, including the position that is supposed to be reverse. My thought is that the transistor that drives the forward relay is shorted. I've heard that these transistors are being operated close to or over their rated limits.
I am awaiting your solution and will be checking the transistors on my board soon.
Roy,
It's locked in forward.
Did you try to unlock the engine?
1. First make sure the battery is or BCR is charged up.
2. While running forward, press the whistle button.
3. While the horn is blowing, turn off track power, either by the throttle off the transformer, or pulling the plug to shut off power.
After a couple of seconds, the bell should sound once. It should be reset now.
It's not "locked in forward". It cycles normally through the forward, neutral, reverse, neutral steps, it just doesn't move in the forward direction. All indications are that it thinks it's going forward, the RPM ramps up as it should, it just doesn't move.
The Battery was replaced by a BCR, properly charged by waiting a minute or so with track power. This is 100% sure not to be a battery issue.
John,
I have been following your post! Hang on! They are coming priority mail!
Good luck & Thanks,
I know, I was just taking a run at fixing this one, can't have too may spares of this electronic stuff. 
John,
I was referring to the engine Roy was having a problem with on just running forward above my post.
I know your problem is on the bottom board.
Joe, I see that now, it gets confusing when another problem shows up in the same thread.
So how did this turn out? I just had a board come in for repair that would not make chuff sounds or drive motor in fwd, but worked in reverse. The transistor for forward is the one closest to the outside of the board. I did my test and it would not power forwrd when jumped. Replaced transistor and it fixed the board.
What was interesting is no motor running sounds (Chuff) for the relay that won't operate. So the processor does look for the motor differential. Also, with no motor attached, the chuff is at a high rate. Soon as you place a motor load on it, the sounds normalize and the chuff matches the motor rotation. G
It's still sitting on my bench, I've been embroiled in a couple of other projects.
I fixed mine. The transistor that energized the forward relay was shorted. It was pretty exciting when the system was cycled into reverse, but both relays were energized.
I fixed this one, I stuck a "replacement" transistor in, all I had was a 2N2907, obviously close enough to the original, now it runs in forward and reverse.
I checked the two transistors with a meter, one has a bogus reading on one of the junctions, turns out it was bad.
I fixed this one, I stuck a "replacement" transistor in, all I had was a 2N2907, obviously close enough to the original, now it runs in forward and reverse.
I checked the two transistors with a meter, one has a bogus reading on one of the junctions, turns out it was bad.
What a guy! Hope your package came today!
Got the package Hugh, do you want them back? It was easier to fix than I thought, I don't have much mileage on the PS/1 boards, but no sweat.
Got the package Hugh, do you want them back? It was easier to fix than I thought, I don't have much mileage on the PS/1 boards, but no sweat.
No John, you keep the boards. This hobby will keep both of us busy long enough so somewhere down the road you will come to my rescue somewhere, somehow!
I don't think some of our forum friends understand what a great thing we have going here, mostly a happy family.
Reading this post is a great example of how valuable this forum is. No one knows all the answers great resource to have. I am just starting out with repairing MTH , GGG has been fantastic guiding me into this. Posts like this are great to help in the learning process. Looking forward to dealing with all of you!
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