Directional Jerky Speed control on PS2 engine, FIXED!!

When it's jerky (in either direction), and you listen for the chuffing sound and watch the driver wheel, do you get exactly 4 chuffs per rev (or whatever your engine is set to)?

Can you run the engine in conventional?  If so, turn off the speed control (Whistle-Bell-Bell followed by the double-toot acknowledgement).  This makes the motor drive "circuit" as simple as it gets with rectified track voltage going right to the can motor. This also takes the speed sensor out of the equation. Now run the voltage up/down in both directions. Is it still jerky in one direction at slow speeds?

Symptoms suggest something funny when the electronics when driving the motor in the "normal" reverse direction.  Very insightful for you to reverse the motor leads.

I'd be surprised if re-loading the soundset would cure this.  That's just my opinion.

I'm not familiar with what lighting goes on your Big Boy but I'm wondering if there's anything that happens in reverse (and not in forward) that electrically interferes with the speed control.  For example, if there are any lights that toggle when changing direction, could their wiring be shorting or messing with the speed sensor board wiring?  Just a thought...

Also, along these lines, there are some steamers that pick off power from the motor connections.  I think there's a small circuit board up in the engine but I don't know what it's called - one of the MTH techs will know.  It uses two diodes (one to each motor connection) of which one is active depending on direction.  So here's another location where motor direction changes the electrical circuit and perhaps some kind of wiring error is in-play.

The upgrade kit derives the P5V signal in the locomotive with a pair of diodes to the motor leads.  This saves them a lead in the tether.

Any board in the locomotive is probably a constant voltage lighting board I'd guess.

Stans point about PV should be checked.  Since switching leads caused the jerkiness to follow when the white motor lead is + I think that rules out mechanical issues when motor thrust changes.

Check the diode lead under the engine PCB that conducts when white motor lead is + (normal) reverse.  G

Still not working, I loaded a different sound set (N&W J) and the engine runs smooth both directions, except if the whistle blown in reverse, the engine becomes very erratic and jerky.  I replaced both diodes in the upgrade harness on the boiler side and still no fix.

This is a standard PS2 upgrade kit with nothing else (no Constant Voltage or MUX boards in the boiler). The smoke unit is disconnected, only the front headlight is attached in the engine, and I disconnected the rear back up light (good test Stan, thank you) but no resolution. Frustrated!!

Any other ideas what might be going on?

Mike

Did you get a chance to compare the chuffing sounds vs. the driver wheel rotation when the motion gets erratic?  So even if hiccuping down the track are you getting exactly 4 chuffs per revolution?

What I think is going on is you're getting noise on the sensor board signal.  This is why I suggested trying conventional operation and turning off speed control so that the sensor board is not used.  With the new soundset, my question is the same.  Blow the whistle in reverse with speed control turned off and do you get the jerky motion?

Aside from any directional lighting, the question is still what is different with reverse operation than forward?  One thing is the direction relay is closed in reverse which while seemingly trivial is an additional load on the 5V supply.  This 5V supply also powers the sensor board as well as the audio amp.  So when you say it is now jerky when the whistle blows in reverse, I'm thinking 5V power supply is somehow on the edge with the combo of the reverse relay and the whistle.  Noise on the 5V line can induce erratic behavior in the sensor board and hence cause erratic motion.

Does the jerky behavior improve if you turn down the whistle volume?

Just tried your test Stan, in conventional mode it appears to not have an issue, but the lowest conventional voltage on the DCS remote is still just bit less than 5V, so it moves pretty good. 

With the sound turned off, but pressing the whistle button in command mode while in reverse, the engine does still become jerky.  

What other options do I have left to try?  

I did not mention that the battery was never fully charged (I would think this is not the issue though). 

Mike, Running smooth with a different sound file is a change.  You had jerky operations in reverse with the BB sound file so now it runs fine until the whistle is blown in reverse.

The battery could be an issue.  It is a load to the 5V power supply for charging.  So either remove it for test with DCS or fully charge it.

What sound file did you use originally?   G

G

I removed the DCS battery and experienced the same results while using the N&W sound file, where reverse and pressing the whistle causes jerkiness

THe original sound set I was using was:

p041pf3bigboy__up_041228afin

The current sound set I am using is :

P042PP3No_608__NW_04072d

I thought maybe it was just the big boy sound set, but try the following Challenger sound set and experienced the same jerkiness in reverse while not pressing the whistle:

p051pp3chal_2r_up_050216afin

I am not sure if the Articulated sound sets are more taxing on the system or not and that is why both the big boy and challenger sound sets had issues with what ever is going on with this board.

With the whistle, I was going down the path that there was something flakey about the audio amp or speaker where high volumes (like the whistle) might draw excessive current and inject noise on the sensor board speed signal.  But since you can get jerking just by pressing the whistle button with audio muted, that's a rabbit hole.

My working hypothesis remains that the speed sensor signal is corrupted under certain circumstance.  If it were in front of me, I would use an oscilloscope to carefully examine the integrity of the speed sensor signal. 

Aside from that perhaps it's time to call in a favor from someone who will lend you a PS2 board set to try?

You do realize that if you load 4.30 you can adjust the starting voltage down from the current 5V default, right?

If you have a Z4000 or similar current-displaying power source, can you see any unusual behavior in loading in forward and reverse direction or when you speed up and slow down the engine?  The digital readout will bounce around more while jerking, but you might be able to get a sense if it's far off nominal. Excessive current draw might validate the wiring/component short idea. 

Even baseline numbers might be helpful to see if there's a power supply issue that is pushed over the edge by reverse operation or whatever.  For example, current draw at 16V with the engine shutdown, when started up with lights/sound on but stopped, etc.

Well,

I am not sure why I did not try this earlier, but I have several other engines I have upgraded, and tried swapping engines and tenders.  The problem seems to follow the tender.

Unless some else has some other advice, I plan to swap out the harness in the tender, and then the board with another engine.  At least at that point I will know if it is a wiring issue or the board.  Has any one ever had an issue with the board like I am describing?

Mike

Since you obviously know your way around the board sets, you could swap JUST the upper power supply board.  That ought to further isolate the problem.

Mike,  As I thought about this doing yard work, the only common components to what you have described is the relay going into reverse and the white wire becoming Positive Voltage and the Yellow pulsed return to PCB Ground.

I Would focus on the Processor board.  I think swapping the processor from one of your other engines and loading the BB sound file and testing.

Before I did that, I would look at the contacts on the motor wires in the 5 pin.  Are they tight and fully seated.  Is there any nick on the motor wires in the tender as routed around heat sink and frame.

I am thinking processor board, or possibly a harness issue.

G

Fixed!!!

I replace the entire wire harness in the tender, using the same speaker, resistor pot and on-off switch, works like a champ.  Examining the removed harness, I cannot see a flaw or stray wire any where.

THanking the group for all your comments in working to resolve this.

On to the next thing, I am looking for an articulated sound set with the same whistle as the N&W J file shown below:

P042PP3No_608__NW_04072d

Any suggestions would be appreciated.

Mike

Thanks for the feedback.  Try measuring between wht and yellow, blue and purple to see  if you have any resistance between one of the combinations.  Could be internal to the harness or plug.  G