PS2 Loco DOA Now Running, but need advice.

Steve, when you run into the old engines like this you are better off to start with a new battery.  Chances of that 15 year old battery taking a charge or doing anything are very slim.  I feel you may have a blown board.  That early board did not hold up good to shorting.

I have removed the electronics and added a rectifier so it runs nicely, forward only which is Ok. Problem is it runs at such a low voltage, the smoke and headlight don't get enough voltage to operate. The loco is running briskly at 3-5 volts. Adding the rectifier is about the limit of my electronics know how, so I'd appreciate any advice on getting the smoke and light working while running.

thanks

Steve

I'm sure others can give some other options, that may be better than this.  That said, try stringing several diodes in series between the rectifier and the motor.  Each diode will drop the voltage by about 0.7 volts, so to start, find what voltage it takes to get the lights up to a satisfactory level, then add enough diodes to get the motors to only start up around that level.  

I'm unsure how big of a motor we are talking about here, so you may want to put an amp meter between the motor and rectifier and see how much current (amps) it draws at full power with a heavy load, or stalled.  Use that measurement to decide what size (amp rating) diodes you need.  (as a note, paralleling diodes is not a great idea to increase the current rating... the physics doesn't quite work the same as resistors.)

A 6amp diode would be overkill on most(a good thing hear really) Radio shack still has those.

Or if you already have another left over bridge or two, or three, that would work also.

A bridge rectifier is just a prepackaged set of diodes.

Use the positive lead from the BR#1 to the neg. of BR#2. Then continue. Pos. of BR#2 to the  neg. of BR#3 etc., But the last positive goes to the motor. EG PosBR#2 to motor.

Using a BR like this is actually paralleling diodes, but it is done often. 

Leave the lights hooked up right where they are now.

Oh, just clip the two ac inputs off BR#2,#3 etc or tape them off if this is temporary.

You've already made a major error by removing the electronics without doing tests to see if the board was in fact damaged.  The electronics provide the proper voltages to the lights, motor, smoke unit, etc.  At this point, you no longer have a DCS loco.

Gentlemen,

   I definitely agree with RJR, you no longer have a DCS engine now, always test before removing!

Better yet send em to an expert like Guns or GGG, might want to add RJR to that repair list also, he has really upped his game in the past couple years.

PCRR/Dave

I understand it is no longer DCS. Everything is saved, so if I chose to get a replacement board or get it fixed, it can be returned to it's original condition. It runs well with the rectifier, I have no problem with forward only. I was hoping for a simple fix to get the light and smoke to operate, but no big deal if it does not. For the price I paid, a big, good looking and good running loco is Ok.

Steve

Hi Steve. The standard diodes on the dc+ side of the rectifier are a simple way to lower the speed, and not have to battle the hi-tech. route.

A resistor could also be used, but I find diodes easier really.

A capacitor on what you have now will smooth any jerkiness you might have (see picky below) 

 Enough amp delivery in the 6amp ones was my reasoning. Almost like choosing a fuse. 6a is likely overkill, but I am guessing. In theory it could need 10a. If 6 amp is the weak link, it will fail.

 E.g., In a repair, you might put a ten amp back in its place if the motor is fine and didn't kill the diode by having a problem. 

Optional work: If you can do a test to see what it draws under a load now, and choose an amp or two higher than that, you will be ok using those too.

  I do the BR thing for one direction too. And use diodes on PW to increase smoke output at lower speeds.

 At the dc side of what you have, all you could do wrong shouldn't burn anything out.

The fix would be face the diodes the other way, right where they are.

 Cut a motor wire, I would choose positive but lets assume we don't know, insert 1 per -0.7v wanted in a chain, facing one way(series). Done. Test. Doesn't work? No- Reverse the diode chain. 

  The 6amp ones are only the size of a shelled peanut. And overkill can be a good thing as diode heat is a byproduct. The bigger one will be a bit cooler on the surface and live longer as it isn't a "weak link" any more than the BR is. But may delay startup a split second that you may or may not notice. That can be fixed if you are picky. I don't think you will pay mind, I don't.  

  That's what I use on PW to make it smoke more at lower speeds too.

Each diode "eats" apprx. 0.7v. Usually a 2-3v drop does plenty. RadioShack packs of three under $3 for a price idea.   

Here's 2 of Dale H's diagrams. One for a diode chain and one that shows the use of the bridge rectifiers next to diodes

These will get a little warm, so give them some space away from the shell.

But that is for ac and reversing. With the BR already in place, and not caring for reverse, a one direction diode chain on one leg of dc is all he needs. Half rectification is another option, But then a cap choice likely has to be made do smooth things more. I think this is simpler, not "the best way ever". Basic was another request. 

Steve,

Did you wire the lights and smoke unit to the rectifier? If so try wiring the lights and smoke unit straight to track power and see what that does. Never run a D.C. can motor on straight A.C. voltage.

If that kills the lights you replace them with higher volt lights.

Lee Fritz

I didn't address the lights and smoke

Are they LED or bulbs.

I don't know very much about MTH smoke units at all. I know they use a 5vdc fan but I don't where the regulation is done. I also don't know how the chuff is activated.

I know nothing about their smoke elements.

I have ideas, but no base info for the MTH "goodies".  

The MTH smoke power to the heater is regulated by the PS2/3 board, as is the fan chuff.  The chuff is generated from counting the tach pulses.