MTH PS1 engine - bypass electronics?

For a single or dual motored engine.use any 6 amp or more bridge rectifier (Radio Shack sells them) It has 4 leads. Wire the pickup roller and frame ground to the 2 leads marked ~. Wire the + and - to the motor(s). The engine will run in one direction only. Reverse the + and - to reverse the motor direction.

A simple E unit can also be used if directional operation is desired. Dallee or Wiliams  reverse units for example will work.

An alternative for dual motored units is to use 2, 6 amp diodes.Run the frame lead to one wire of each motor. Run the pickup wire to the + lead of one diode and the - lead of the other. Run the remaining 2 leads to each motor. Reverse if it runs in the wrong direction. Each motor will receive half wave pulsed DC and run similar to series wired motors without the drawbacks.

Dale H

Thanks Dale,

So you're saying that all MTH can motors are DC, and there is a rectifier built into the engine's circuit boards:  if the boards are bypassed or removed, a substitute bridge rectifier will need to be used?  (please let me know if I have misunderstood). Is this true also of MTH standard Gauge locomotives?  For standard gauge, would the amperage recommendations for the rectifier be the same?  

Thanks for the clear directions.  I can follow these.

Yes

As far as I know all MTH motors are DC. Rectifier is in the board.  6 amp or more should work for most all. Dont have any MTH standard gauge perhaps others can chime in. Cant imagine it pulling more than 6 amps. 

Lionel PW type AC motors will also run on DC. Installing a rectifier if it can be fit in will make the motor run a bit smoother.

Dale H

All "can - type" motors of any brand are DC motors. The permanent magnet field makes the motor DC. The locos run on AC because there is a rectifier in the reverse unit, among other things. other

The "AC" motors in our old trains are actually series wound universal motors that can run on AC or DC. With the exception of the motor in the Western Coil and Electric Zephyr and its Consoli family remakes. There are most likely other exceptions as well.

Thank you again Dale, and Roy.  This sounds like something I ought to be able to do.

I have rebuilt a couple of Proto 1 engines. Best advice would be to use the Williams 6 Amp board.

What's wrong with your PS1 board?...die out or just not happy with the performance..just curious.

Hojack, for a PS-1 system the top board can be removed and a switch can be wired into 4 of the terminals to manual control the board.  This retains your directional lighting removes the sound and battery portion of the PS-1 system.  It will not act as a reverse unit automatically, but manually as you said you would do.

If the bottom board is bad, then you can do what Dale said and put in a FWBR and the engine will run in one direction unless you wire in a switch to reverse polarity for manual control.

The other option if you want an electronic basic reverse unit is using the Williams or a Dallee as mentioned.  Or finding an old QSI/MTH DCRU which was the electronic reverse unit bottom board.  G

I'm with George here, the easiest way to have working reverse would be something like the Williams board.  Just four wires, pickup, wheels, and two for the motor(s) and you're off and running.

hojack,

email sent. 

Sunrise

I recall reading on the OGR Forum a while back that the can motors MTH use in their PS2 and PS3 systems see a maximum of 12 volts. 

  -  Is that a correct statement ?

  -  If it is,

          - are PS1 motors the same ?

          - should precautions be taken to ensure the motors don't see excessive voltage ?

          -  If 12 volts = top speed, that would suggest wiring the motors in series [ if dual motored ] or adding a dropping resistor might be beneficial ?

I am thinking about doing the same thing, but to PS2/3 locos.

Best regards, SZ 

SZ

The neutral board automatically adjust voltage. The last PS1 engine (Weaver) the board was fried. I used a Williams board as a replacement and that powered the motors in unison. There should be a separate small board that controls the reverse lighting. I had issues getting that portion to work right and maybe someone can address that issue. But the engine ran like a champ after the conversion.

Doug 

That's good to know;  but what about doing it "Sans electronics" except for the bridge rectifier or similar as in Dale's first post above ?

SZ [ who would actually use track dc to allow remote reversing that way ]

If you want to "play it safe", just use a single diode, you'll get half the effective voltage and there'll be no danger of getting 12 volts effective voltage.

If you go the simple bridge or diode approach, you might consider a latching relay to handle direction. You can use cheap low-current reed switches to change directions by waving a magnet near the shell rather toggling a (possibly) inconveniently located mechanical slide switch.  While it may seem convenient to re-use an existing switch and its cut-out, many of these control switches are not able to handle the current of a motor.

If you're going to all the trouble to do a bridge and latching relay, why not do a real reverse board, they're around cheap...

For dual motored units,you can use 2 diodes instead of a bridge as described in a previous post. I do not think PS1 boards regulate voltage to the motor at all other than the voltage drop of the bridge rectifier in the board.

For single motored or dual motored units you can also use a bridge rectifier or reverse board and voltage dropper,described here. For uni direction using a bridge only a single string is needed in one direction. Described here

www.jcstudiosinc.com/BlogShowT...=488&categoryId=

Not only will the addition of the diode string restrict voltage to the motor,tapping the 2 ends of the string will provided constant voltage lighting for an LED or light bulbs. If a reverse board is used the lighting can be made directional.

Dale H

Actually some of these motors are rated to 18VDC.  Frankly I think if you got the voltage too high the train would be moving too fast and fly off the track thereby saving the motor:-)

As far as the switch, when using a switch to control the bottom board of a PS-1 you are just using it to control the transistors that control current to the relay coil.  Low voltage and current application  (5VDC and less then 100ma). 

The PS-1 system does drop voltage via a series of diodes.  The Bridge is used primarily for control circuits and half does feed 2 large diodes for each motor lead.  So you do get a drop of around 2.8 volts (4x.7V)  It is one of the advertised features of slower starts then other reverse units.  Nothing like CC with cruise but better then many other units for conventional control.  G

I recently finished a steamer that started out as just the chassis with DC motor from a Weaver brass 4-6-0.  The QSI electronics were in a bag.

I extended and mounted a MTH 2-8-0 boiler to the chassis and connected the 4 pins on the wiring plug at the rear of the cab so that I could run the engine on my 3-rail layout, using a old HO DC power supply (Troller Transamp 1).  I connected one wire to the outer rail and the other to the center rail, works great!

I even hooked up an old Aristo-Craft Train Engineer handheld throttle that hasn't been used in at least 15 years and that worked great too.  I can control the speed by using just the Troller unit and turning the knob, or pressing the buttons on the TE handheld unit.  Direction is controlled by moving the switch on the Troller unit, or pressing the buttons on the TE.

No action movies, but here's what the engine looks like now:

I still need to put a headlight and number boards in, but she's capable of going round the layout on straight DC.

There's no reason to have a shelf queen unless it's mechanically broken, the electronics can always be dealt with.

Im a bit confused here 2 diodes without a bridge rectifier (if used only for control circuits) would half wave each motor. Each motor would receive half waved pulsed DC. Drop would be 50% (RMS) plus .7 volts. If a bridge is used for the motor, 2 diodes (one in each direction) would simply drop .7 volts.

Dale H

The + of the bridge feed 2 6 Amp diodes in series to one motor lead via one relay.  The other lead is feed + voltage by 2 separate diodes in series and a second relay.  The relay feeds either the + voltage to the motor or return to DC ground.  The relays cycle the motor lead (one to positive while the other goes to ground and alternates for reverse.  During a neutral state both leads go to the same potential and polarity.

Hence 2 x .7 drop via bridge and 2 x .7 via individual diodes.  G

Thanks GGG

If you could post a schematic I would appreciate it. I always assumed those 4 diodes just made up a bridge rectifier.

Dale H

Dale,  They are crude notes and drawing I maintain.  Basically, the AC input goes to the square FWBR first an that creates a DC circuit.  Off the +DC of the square bridge there are 2 6A diodes in series that feeds one of the Motor Relays.   There are 2 6A diodes off the +DC of the Square that feed the other Motor relay.

Either the logic circuit of a DCRU controls the relays to alternate which motor lead gets the + DC voltage and the other is sent to a DC Ground return or the TOP Protosound board controls the relays.

The primary difference between QSI and MTH version of ProtoSounds are:

QSI always has the logic chips on the bottom board but doesn't have a Power Supply to drive the Top board.  That is why for a QSI system there are 3 boards for Sounds.  The middle is the Power Supply for the top board.  In a QSI system you can remove the top two board and then the bottom board reverts to a Basic Reverse unit (DCRU)

For MTH Protosounds there is no logic on the P4 bottom board.  Instead it has the Power Supply for the top board and the Coupler circuit built in.  The Top board is required to have the automatic reverse function.

If you do remove it, you still can make it function as a reverse unit via a manual switch.  The switch provides the 5VDC to turn on and off the 2 small transistors that actually energize or de-energize the 2 relay coils to flip the motor lead power source. 

For MTH engines that only have a horn or bell, the bottom board was a QSI DCRU with a horn/bell board plugged in. 

You can't just plug in a MTH top board because the DCRU doesn't have the power Supply to drive it.

The back end of the DCRU and the bottom rear of the MTH bottom board have various pick up points where directional voltages can be picked off and diodes and resistors can be added to create 1.5VDC for bulbs, 3VDC and 5VDC for LED.

To me it really is an interesting design considering it came from the 80s when even lionel didn't have directional lights on a reverse board, in fact I don't think that happened until TMCC and only now with some of the boards being put in conventional engines in the 2010s.

Hope that helps.  G

Thanks G

Obviously you know these boards.

Dale H