e unit problem on whistle only unit

Have you eliminated the mechanical reasons?  Try manually turning each motor in the reverse direction through at least a couple wheel rotations of the power truck(s) and see if there's any binding.

Usually not too much binding on diesel but it is worth trying what John recommends and make sure one of the trucks isn't binding in reverse, possibly when the motor shaft moves vertically.  Also make sure the motors are secure, check the screw under the truck that holds the motor to the truck.

If that is all fine with no binding, than the board uses a small transistor to cycle the relays.  It is possible one is bad and the momentary cycling of one is giving you your short pulse in reverse.  Or the relay may be bad.  Finally the Logic circuit chip may have a bad segment for reverse.  All these can be fixed.  G

Thanks John, and everyone else who has responded I turned the motors by hand in a reverse position and there is no binding also checked the screws on the motors to make sure there tight Next is the board which I have ABSOLUTELY NO KNOWLEDGE .but I guess its time to learn

What's the exact model of this unit.  A replacement reverse board is probably not a major expense for a whistle-only unit, and you can probably pick up a used one in the forum for peanuts.

Model doesn't really matter for MTH.  This is a conventional PS-1 and they used the DCRU which is no longer carried by MTH.  So you have to go to the secondary market, or repair the board.

The 5087 transistor (there are 3), but only 2 are used for controlling the relays.  Of course it can be a burned trace, or micro controller too, so unless your familiar with electronic it may be a little intimidating.  If you want you can send me the board and I can test repair. Or sell a DCRU.  E-mail is in my profile.  G

John the model is RK2004 santa fe with a dcru by QSI

GGG how can i learn how to fix this stuff myself

Most likely the transistor 5087 that is between the Yellow Marker plug and the Relay needs to be changed. (Small circular transistor with 3 legs at the outside edge of the board)  That controls forward motion.   G

Do some searches on basic electronics, that you need to spend hours tracing how these boards work.  When I say hours, I mean hundreds of them.

If you go to a manufactures tech school, they will give you some of the basics, but even they don't get into full component repair.

Doing this as a hobby, and tracing these boards has lead me to know what components control what, what leg or pin of a chip goes where, what traces tend to burn and what they do, so that I can repair at the component level.   I just fixed one yesterday same symptoms.   I have a procedure to check the micro controller, if it's output is good I test the transistor.   The transistor is a good starting point.  IF this is beyond what you want to do, you can send me the DCRU and I can repair and send back.  G

GGG someone said it may be better to just replace the entire board with a dolly reverse unit and get away from QSI whats a dolly is that the MFG

It is a type of electronic reverse board.  Every manufacture can have a failure, especially engines that are as old as PS-1.  There is nothing wrong with QSI and it has provisions for directional lighting.  G

I got a real hoot outta' that one! Old? You are kidding, I hope. That's like brand new!

Rob, Please stick to post war repair, your better at it.  For electronic age matters and failure do occur.  And electronics aren't the same as electrical.  I am pretty sure finbar is looking for value added post.   G

It's just a sad commentary, really, on what to expect out of our new $1K locomotives being purchased today 15 years from now.