MTH F-7 will run forward or backwards, but not both

I believe that PS3 doesn't have a polarity switch installed. Wrong! oops!

What power pack is he using? Is it a switching type?

"Conventional DC Operation Your MTH locomotive will operate on conventional DC track voltage also. However, functions such as sounding the horn, ringing the bell and the PFA sounds cannot be initiated in conventional DC. Only the engine sounds, smoke, squealing brakes and idle sounds will function. Operation of your MTH Proto-Sound® 3.0 engine in conventional DC is very similar to operating a conventional AC engine. As you increase track voltage, engine speed increases. As the track voltage is decreased, engine speed is decreased. When track voltage polarity is reversed using the polarity or direction switch on the power pack, the engine will run in the opposite direction. The electronics in your MTH Proto-Sound® 3.0 locomotive are designed to slowly change direction without a need to change the throttle, if you so desire. Just change the polarity switch on your DC power pack and the engine will gradually come to a stop and then automatically begin traveling in the opposite direction. The speed will build up to the same speed that the engine was going in the previous direction. When power is first applied to the locomotive, the engine’s sounds will start up when the track voltage reaches about 8 VDC. To get your locomotive moving, after the startup sounds have finished and the locomotive is idling, slowly increase the track voltage until the locomotive is traveling at the desired speed. NOTE: If you apply more than 9.0VDC to the engine at start-up the engine will not move. This is normal. We refer to this as “Anti-Jackrabbit” and this feature prevents your model from taking off at high track voltages. Simply lower the track voltage down below 9.0VDC and then back up to get your engine moving. This applies only when you start up your engine. "

The MTH F units have a switch, so that you can run them back to back in DC, and they will go the same direction.  ie..one forwatd and one backwards, at the same time. 

  But  the issue here is..He has just 1 F-7, trying to run it in analog DC.  He put it on the track, it runs forward, no problem, everything is perfect.  Then he switches the polarity on his DC analog transformer, and the engine should run backwards, but it just sits.    Yes, it sounds like a circuitry issue.   Just wondering if anyone else has had or has heard of this issue?

thanks

beth

@Engineer-Joe posted:

I believe that PS3 doesn't have a polarity switch installed.

Joe, I just received my F3 powered A-unit (thanks Beth!) yesterday.  There is a Polarity Switch on these F3's.  The operator's manual for the Premier F3 & F7 Diesels states that this switch is used to set the correct motor direction for multiple engines running in a "tail-to-tail" arrangement while operating in "conventional mode".  There's also a Headlight Direction Switch.  Here's a direct quote from the manual...

Conventional Powered A-A Operation Configuration

To operate two Powered A-Unit models in the traditional "Tail to Tail" arrangement in Conventional Mode, the headlight and motors of the Trailing A-Unit Locomotive must be configured to allow the Trailing A-Unit to start up and follow the Lead A-Unit correctly.

Unfortunately, this still does not answer Beth's question as to why her customer's engine will only operate in one direction.

I just put a Z1000 with a bridge rectifier for DC, to power my F series with PS3. I didn't see any polarity switch on the lead F. I will look closer.

It has a trailing A unit with a slave board inside I believe? I didn't look at that one.

Later series were only offered as A masters. So maybe they too had a switch?

It ran as advertised with it reversing direction after coming to a stop when I swapped polarity.

I'd have to believe that the tech at MTH was correct about the type of power he's using.

So what is he using?

Sorry!

I see the switch in the manual labeled direction switch on page #9.

_F-3 & F-7 Diesel 2015.cdr (mthtrains.com)

To operate two Powered A-Unit models in the traditional “Tail to Tail” arrangement in Conventional Mode, the headlight and motors of the Trailing A-Unit Locomotive must be configured (see illustration below) to allow the Trailing A-Unit to start up and follow the Lead A-Unit correctly. Additional Conventional Powered A-A Operational Notes: 1) The Trailing A Unit Mars Light (if equipped) will operate (Flash) when the Lead A Unit is going forward but will be out when the Lead A Unit is going in reverse. 2) To fire the Proto-Coupler on the nose end of the Trailing A Unit, use the Conventional AC Operation Front Coupler Command – 1 Bell tap plus 4 Whistle taps – as described later in this manual. Please note that this command will fire the Proto-Couplers on the nose ends of both the Lead A Unit and the Trailing A Unit. The Headlight Direction Switch (HDLT DIR) should be in the Rear (R) position. The Motor Direction Switch (MTR DIR) should be in the Rear (R)

here's my (older?) set, yet still with PS3.

22-20404-2 | MTH ELECTRIC TRAINS (mthtrains.com)

They are configured for running only one way. No direction switches. The tethers only work with units oriented one given direction.

So that's what I based my answer on.

F-3 & F-7 ABA Diesel (EXPANDED DCC) PS3.cdr (mthtrains.com)

Newer releases don't have the tethers. Those have the switches I imagine?

Mine work as advertised.

The newer F-units were not tethered as they were sold as separate, stand-alone locomotives. I don't run DCC, but I'm wondering if the customer is trying to use DC with the DCC/DCS switch set to "DCC". It should be set to DCS for conventional AC or DC operation. The 2-rail/3-rail switch should be set to 2-rail . I did run a couple of my PS3 diesels on a 2-rail DC test track and they ran fine in both directions with engine sounds only.

@Beth Marshall-The Public Delivery Track posted:

...

I have a customer who bought an MTH F-7, 2 rail Proto 3.  He runs analog DC.   The unit will run forward, but not backwards, or if the polarity switch in the back are switched, it runs backwards, not forwards.

IF engine is lifted off track and faced in other direction, does it behave same (except backwards)?

The other switches are in "2 rail" and "DCS".  All the sounds, etc are working properly.

In later post you say it "just sits" when the track voltage is reversed.  I assume you mean with sounds and lights running...or does it "shut down" and go dark/silent?  Does this mean the engine smoothly came to a stop with diesel rev'ing sounds smoothly ramping down to the lowest notch.  If engine has directional lights did they flip direction?

He called MTH and i believe they are telling him that this engine just will not work with his power supply, and that he should return it to me. 

What is "his power supply"?  Are they saying this would work with some other power supply...is there a recommended DC transformer list like MTH  provides for AC operation?

Only other thing is that he did try to run it with analog current in "DCC" mode originally.  Is there any chance this could have messed the unit up?

I can't speak to the PS3 implementation, but DCC engines should be able to tolerate DC since that is one of the operating configurations specified in DCC.  That is, I'm not a DCC expert but DCC engines I've seen can be set operate in Analog DC mode behaving like a conventional DC engine with the DC track voltage polarity/voltage controlling direction/speed.

It is "known" that MTH engine don't get along with certain transformers. It will confuse or even scramble them. MTH includes a list of approved transformers for the engines. There are more transformers that may work than on the list.

I believe the main problem is called chopped wave? If that's what he has, it won't work reliably.

I have Bridgewerks DC transformers for my G scale that work great. I can also use a bridge rectifier on my MTH AC packs. Seems like ones with good clean stable power work. I have some MRC DC packs available for testing but I'm casting pilots right now.

So I asked what he's using to see if I have it here as well.

That's correct.  There is an analogy with "pure sine" AC transformers and "chopped sine" AC transformers.  I have a Bridgewerks Magnum which says right on it "PURE DC POWER"... while there are "pulsed DC" supplies that output unfiltered pulse-width-modulated (PWM) DC.  I suppose this could be called "chopped wave" DC.

@stan2004 posted:

That's correct.  There is an analogy with "pure sine" AC transformers and "chopped sine" AC transformers.  I have a Bridgewerks Magnum which says right on it "PURE DC POWER"... while there are "pulsed DC" supplies that output unfiltered pulse-width-modulated (PWM) DC.  I suppose this could be called "chopped wave" DC.

I just looked at the manual from my PS3 GP38-2's and there's a warning about PWM regarding use with TIUs -- a warning that it will damage the electronics. It would not surprise me if it drove the PS3 boards nuts. I think you're onto something here.

I was not satisfied by how my MTH Proto Sound engines ran on DC so I installed a Z-1000 in every DC power block with a d.p.d.t. switch to select power source desired.  No operational issues using the Z-1000.

DC provided  inadequate performance IMO.

All my G scale runs reliably on DC provided from Bridgewerks packs. Both inside the house and out.

All my engines get upgraded to MTH command control boards inside, as I can.

E.  Joe, now THAT'S real model railroading!!  How about an overall view of your outdoor pike??  Great job on the scenery.

There is no "transformer" involved here. The guy is running a simple DC power supply. It outputs DIRECT CURRENT, not ALTERNATING CURRENT. There is no sine wave to chop up. A DC waveform is essentially a straight line.

Thanks

Hmmm, overall? I have separate videos that show all around the yard.

FWIW....  The power supply into the transformer is AC, so it has to be rectified into DC current. Cheap transformers may use a diode only for this, creating a pulsing DC current , also known as half wave DC.  There is a slight wave to half wave DC, as u are transmitting 50% of the AC current that all moves in 1 direction, only.

  A good transformer uses a rectifier bridge, which results in continuous DC current.  This is full wave DC, which is a straight line of DC transmission

I think there is just some incorrect use of electrical nomenclature.

So....still.... what is he using for power???

@Rich Melvin posted:

There is no "transformer" involved here. The guy is running a simple DC power supply. It outputs DIRECT CURRENT, not ALTERNATING CURRENT. There is no sine wave to chop up. A DC waveform is essentially a straight line.

Actually, we don't know what the guy is using.  Hence, for the nth time:

@Engineer-Joe posted:

So....still.... what is he using for power???

What he said!

MTH - DCS Tips and Operating Help (Digital Command System + Protosound) (rayman4449.com)

If I may post from Ray's pages

- DO NOT USE:

                    - Power supplies with Pulse Width Modulation/Pulse Width Control (PWM/PWC)

                    - Bridgewerks "Mag 15" direct connected to the track or TIU (Mag 15-R is safe to use)

MTH - DCS Tips and Operating Help (Digital Command System + Protosound) (rayman4449.com)

   Avoid/Do not use:

          - Pulse Width Modulated (PWM) power supplies   

          - DO NOT USE PWM power supplies!

          - PWM will Damage your MTH TIU and possibly PS2/PS3 engine electronics.

          - Will also cause severe control/operational issues because of the PWM/PWC power.

          - Note: If you are unsure if your power supply is PWM, contact the Manufacturer to confirm if it is Linear or PWM/PWC.

          - Aristocraft Revolution Base Station (added between your power supply and TIU/layout that allows control/regulation of track voltage):

          - Model #57005S / 57004S is PWM/PWC output (Do not use!)

          - Model #57007S / 57006S indicates it is Linear (not PWM) and would be safe to use

          - MRC Throttle Pack 9950 or 9900 (These are PWM power supplies, Do Not Use!)

          - Bridgewerks Mag 15 (old version with unregulated output of 35+ volts)

          - Caution:

          - Aristocraft Train Engineer (At least some are PWM/PWC) (if it has a Linear/PWC switch, do not use on PWC setting. Linear would be ok)

          If you aren't sure if your Train Engineer is PWM/PWC or Linear, then I would assume it is PWM and not use it until you confirm for sure.

                              Caution/Notes:         

          - USA Trains Power 10: 

• Testing shows this power supply has excellent track signal results and is one I normally recommend under the Good to Use list.  However as of 3/27/19, I have encountered 3 separate customers within a few week period where engines stop running with their lights flashing/pulsing (PS2 or PS3-One gauge steam) .  Engine won't move with speed dialed in and engine makes noises when on the track.  It appears USA has a bad batch of power supplies where they have an intermittent problem where they pulse track voltage on/off to the track rapidly.   If you see this STOP USING THE POWER SUPPLY IMMEDIATELY!  (Note that if you have PS3 with LED lights then lights wont flicker/pulse but will malfunction/not move.)

Customer has

@Beth Marshall-The Public Delivery Track posted:

,,,

Seems that the power is only getting to the motors in one of the 2 polarities.  Dont know the circuitry well enough to figure what is causing that, but it seems to me like its going to be a trip back to MTH for a board.

...

I previously asked if the lights and sounds "work" when the engine just "sits there." If by "sits there" the engine is dark/silent then you may have a problem with the DC power source.

For example, I have no experience with your Crest 5471 but if this pic depicts what your guy has, I see there is a Linear-PWC selector.  Does it behave the same in either setting?

Also, since your guy has a Bridgewerks PURE DC supply, did he directly connect the Bridgewerks to the 2-rails (no Crest 5471) to see if the MTH engine behaves differently?  In other words I think it prudent to confirm the problem is in the MTH engine before shipping it off.  I think it's worth the time to confirm the MTH engine does or does not go both directions when directly powered by a PURE DC supply using the Bridgewerks direction toggle switch.  Bridgewerks is (in my opinion) essentially the gold-standard for PURE DC train control...so  it's somewhat puzzling that MTH said it would not work with "his power supply"...or maybe I misunderstood your initial comment.

@Engineer-Joe posted:

So....still.... what is he using for power???

From post no. 3...

”...He has just 1 F-7, trying to run it in analog DC...”

For clarity,

Is the problem:  using Pulse Width

or

Is the problem: does the power pack have  the  Pulse Width option?