Skip to main content

All,

I have a PS2 Premier UP SD70ACe (20-2918-1) that I bought new a couple years ago.  I haven't been able to run it a lot until recently, but I've noticed a strange anomaly that my other PS2 engines don't have.

When under load (meaning pulling a fairly heavy train) it "surges" quite heavily and constantly until you get past 8 SMPH.  By surging it slows down to the verge of stalling, then it rapidly accelerates up to the programmed speed.  If it's only a very light load, for example only pulling itself or several cars or if it's part of a lashup where the other engine(s) appear to keep it under control it seems to be fine.  Once past 8 SMPH it seems to stabilize itself, although I can sense that it still surges very slightly (maybe more like subtly) as I can hear a slight increase in speed and slowdown by listening to the sound of the wheels of the entire train on the rails. 

I've taken the shell off to look at the timing tape and verified it's clean and no smudges or missing stripes.  I've also checked the tach reader and it seems to look okay as well.  I've tried doing feature and factory resets, and even tried re-installing the sound file from the PS2 site (and yes I verified the sound file is the correct one).  Everything else, sounds, lights, couplers, etc. all seem fine.

This is being run on an 8 x 15 layout using Atlas O track and switches, wiring was carefully done per DCS best practices (including Barry's book), current TIU and remote software versions installed.  Again, none of my other dozen or so PS2 engines are encountering this symptom.

Any thoughts?  I'm almost inclined to think it's something with the tach reader but I wanted to get other's input as well.

Thanks!
Original Post

Replies sorted oldest to newest

John,

 

Is this your only Premier engine with the newer 6 axle 3/2 drive system?

 

I ask because I have three Premier diesels(6 axle 3/2 drives) that display similar behavior.  They are from different years(2006,2009,2010)so it seems more than coincidence that they all three don't perform as well, compared to the pre 2006 Premier and all Railking models that I have. 

 

The only difference I can see is the drive system and the 3/2rail convertible setup. 

 

Recalling Barry's remark concerning porous paint strips on flywheels, I put a new tach tape on one that was really messed up, and went over the strips on the other two with a fine tip marker.  While it did improve things, they still seemed a little "sluggish" to respond to load change, compared to previous Premier/all Railking models.  

 

This is my first experience with the Premier 6 axle 3/2 drive system that came out(I'm told) in 2006.   Just last month I purchased a NOS 2005 Railking scale FP-45.  Since it employs the older drive system, I expected smooth and steady, and it does. Put your finger in front of it and it'll just push it out of the way. It earns a big .

  

I have a new PS3 Dash 9 due to arrive next week(hopefully).  Since it employs the same 6 axle 3/2 drive systems, I am keeping my fingers crossed that it will perform better with the PS3 system.  

 

I don't know; maybe I'm being too picky.  After all, the "three" have excellent sound packages; even the PFA talk sounds more realistic.  And once up to 6-8mph they run fine. 

 

 

 

 

 

 

 

 

 

 

Last edited by Mike Norberg

Mike,  Is the gap on the tach reader larger for the 3 than other PS-2 engines, or is it close to an edge?

 

The tach read can be adjusted by desoldering, but there is a maximum.  I find Tach reader spacing to be an issue with some upgrades especially the larger pitmann motor with small flywheels.

 

I have used Goo and tie wrap to secure a tach reader to the motor vice the holder when the holder gaps the reader to far away from the flywheel.

 

The only things I can see as issues if this is systematic to these engines is gearing, tach reader gap, or a software issue in the engines profile. G

Originally Posted by Mike Norberg:

 

 

  

 

I have a new PS3 Dash 9 due to arrive next week(hopefully).  Since it employs the same 6 axle 3/2 drive systems, I am keeping my fingers crossed that it will perform better with the PS3 system.  

 

I don't know; maybe I'm being too picky.  After all, the "three" have excellent sound packages; even the PFA talk sounds more realistic.  And once up to 6-8mph they run fine.

 

 

 

 

 

 

 

 

 

 

I have 3 dash 8's with proto 3 and they all seem to have the same problem but to a lesser degree then John's. They hesitant to about 4 SMPH and smooth out at 5 or 6 mph. It must be the 3/2 system causing this. I see nothing else that could.

Mike,

Yes I do have some recent 6-axle Premier diesels with the 3/2 system, they're all SD45T-2s, (scale wheels), and they're actually amongst the smoothest running engines I have.  None of them exhibit the same trait as the SD70ACe, so I have my doubts it's the 3/2 system itself.  It's not sluggish or jerking behavior that's being experienced.  It's just a constant cycle of drifting to a near stall then rapidly accelerating (surging) back up to original speed repeatedly when pulling heavy trains until it's at or above 8 SMPH.  It's like it's having difficulty self-regulating at those lower speeds.  It's not from a lack of track power (I use a Z4000 with both posts powering isolated loops on an 8X15  layout and use auxiliary transformers for buildings/accessories).  There's no gear binding that I can detect either.  I'm a bit perplexed with this one, and it's a bit frustrating if not annoying.

Having said that, and along the lines of your comparison between the early PS2 engines and the more current ones from approx. 2007 on, what I have noticed is that the earlier PS2 engines do indeed appear to have better operating slow speeds below 4 SMPH than the newer ones.  I have a few of the early PS2 Dash 9s, and I can get pretty decent crawling speeds without any jerking between 2-3 SMPH.  The latest ones however, at least from my own observations,  only seem capable of this at or above 4 SMPH.  Main difference is that the early PS2s are 5 volt and the newest ones are 3 volt.

But then again, maybe the sound/personality files being used is contributing to it?  Now that I think about it I have one early PS1 Premier GS4 Daylight engine converted to PS2 (3 volt) and the original sound file downloaded could crawl decently between 2-3 SMPH, but it lacked the crossing grade feature so I tried a more recent GS4 sound file and got the crossing grade sound sequence I wanted but then I noticed that it was more jerky between 2-3 SMPH than the earlier sound file, go figure? As far as I know the wheel diameter and gearing hasn't changed in the reissues but I could be wrong.
Last edited by John Korling
Originally Posted by John Korling:
When under load (meaning pulling a fairly heavy train) it "surges" quite heavily and constantly until you get past 8 SMPH.  By surging it slows down to the verge of stalling, then it rapidly accelerates up to the programmed speed. 
Any thoughts?  I'm almost inclined to think it's something with the tach reader but I wanted to get other's input as well.

John, when time permits, I'd be interested in the following two experiments which shouldn't take long.  Run engine under load:

 

1. in conventional at 8 sMPH or thereabouts - probably around 10V or so.  Is the surging behavior any different?

 

2. in DCS at 8 sMPH.  Lower track voltage to 12V or so.  Then up to 18V or so.  Does surging behavior change?

 

This is simply an attempt to further slice the pie.  

 

 

Have any of you actually pulled the shell, rotated the motor and looked closely at the gears?

I had a similar problem in a steam engine that I found a bad gear in.

I had to clean the gear up with a jewelers file, it was very rough in one part of the rotation.

That motor eventually failed and was replaced, I wonder if the true cause was that gear.

Thanks for the responses so far guys.

The tach reader visually looks to be within proper distance from the flywheel but I'll check it again, however the newer PS2 engines have a redesigned plastic mounting bracket for the tach reader that clips onto the can motor, it seems to be designed so that the tach reader remains in a fixed position so that it stays within tolerances, unlike the earlier mounts that was a separate long thin metal piece where the base attached to the frame that were susceptible to getting tweaked (bent) where it can be too far inwards or outwards.

Stan2004, I'll try the conventional approach to see what happens with that and report back within the next couple of days.  Likewise RAK I'll try reseating the plug as you recommend.

Russell,

The motors turn freely, no binding, gears all visually look ok.

Thanks again guys, will keep you posted.
Originally Posted by John Korling:
I still need to test it under load in conventional, I'll try to get to that this weekend.

Thanks again guys, any other thoughts or suggestions are always welcomed. 

 

Hello John,

 

If possible also see how it behaves under load in command mode at the problem speed if you lower track voltage to 12V (or whatever voltage will support the speed given the load) and then increase the voltage to 18-20V.  All this in command mode so changing the TIU input voltage to a fixed channel for example.

 

Regarding the sensor. Have you confirmed it runs at the right speed? Since 1 sMPH is 0.367"/sec, if you command the engine to, say, 5 sMPH and run it for 30 sec, does it move exactly 5 x 30 x 0.367 = 55 inches?  Probably best to do this with an unloaded engine where it runs smoothly.  Adjust the numbers for what's easy to measure on your layout such as a long straight section.

Stan,

 

I just got back upstairs from testing in command mode, starting from 12v and the speed on the engine set to 4 SMPH on the remote.  Engine is stalled, lights flickering, and I could hear the can motor armatures buzzing, not a good thing.  I crept the juice up to approx. 13.v, it started to crawl very slow and steady (less than 1 SMPH from the looks of it) and it remained that way, maybe speeding up to approx 1 SMPH as the voltage increased but remaining steady up 17.5v.  This entire time, the lights were dim or flickering.  Once I hit 18v and higher, the engine took off like a jackrabbit and then resumed it's original surging symptoms.

 

I repeated the same tests a few times, this time adjusting the engine speed on the remote higher for each one (10 SMPH, 20, and so on).  Each time, from 12v up to approx. 17.5v and got the same results as the first test.  Some of the subsequent tests the engine kept crawling at ~ 1 SMPH or less through the entire voltage range, even over 20v.  If I gave the train a slight push to take up the slack a bit then it would take off quickly for about a foot or so then settle back to it's original surging symptoms again.  After this I called it a night so I didn't do the same above in conventional mode.

 

When it is operating "normally" by not pulling a heavy load or only itself it appears to be pretty close in speed to my other PS2 engines.  Early on when I noticed the original symptom I actually did run it for several laps with a couple of other engines with a few feet distance apart from each other and they kept pretty close in speed together from 3-4 SMPH and higher.  The problem engine certainly didn't display any behavior indicating it was way off.  Same if I had a full heavy train on the other engines and ran it by itself.


So what do you think based on above?

Stan,  While all this seems neat, where does it lead?  There are no schematics to isolate a component on the board as an issue.  Wouldn't it be easier to pull all the harnesses except the 7 pin (power and tach) and the 5 pin (motor) and see how it runs.  This eliminates those possible grounds in lighting, smoke and sound.  If the engine runs fine, then install harnesses one at a time until problem comes back.

 

If still bad, replace the tach reader, though this should also cause sound issues.  If still bad, and you are sure nothing mechanical, then replace the processor board.  G

John, I have noticed on my Proto 3's that they have started to smooth out. Most of the time they just don't start moving until I reach 3 or 4  MPH but they do start smooth, no more hesitating most of the time. What is causing this, I just don't know. I have taken them apart and they seem normal. Maybe they need a longer break in period then before but time will tell. 

Originally Posted by GGG:

Stan,  While all this seems neat, where does it lead?  There are no schematics to isolate a component on the board as an issue.  Wouldn't it be easier to pull all the harnesses except the 7 pin (power and tach) and the 5 pin (motor) and see how it runs.  This eliminates those possible grounds in lighting, smoke and sound.  If the engine runs fine, then install harnesses one at a time until problem comes back.

 

If still bad, replace the tach reader, though this should also cause sound issues.  If still bad, and you are sure nothing mechanical, then replace the processor board.  G

Hello G,

Well, hopefully all this leads to a smooth running SD70. The reason for my "neat" experiments is because I don't have access to his engine in which case I'd use other tools and methods. So I'm suggesting experiments which should be easy and relatively quick to perform. Based on the mechanical experiments others have suggested, I'm convinced there is an electrical problem.

 

If he were to perform no further experiments, harness removals, or whatever, I agree it's time to start swapping board(s). I don't mean to suggest trying to isolate to a specific component.

 

In John's first post, he suggests the problem is the tach reader.  I haven't given up on that either. My last suggested experiment was to move the 3-wires to the tach reader. As you know, the tach reader is just an LED bouncing light off the stripes back to a phototransistor.  With no schematic necessary, my logic is the current-transfer-ratio of photodetectors like this is less than 100% so the level of currents flowing in the tach wires must be just a few mA.  If you run these wires next to high-current wires carrying pulsed currents 1000 times greater (a few Amps under heavy load), I'm speculating that extra tach pulses could be induced causing the engine to slow down under speed control.  As shown below, in a diesel but not Premier SD70, the 3-wires (blue, org, grey) from the tach-reader go down the motor and co-mingle with the 2 motor wires (ylw, wht) and disappear under the boards.  I'm suggesting he redress the 3-wires so they run by themselves, physically separated, direct to the tach reader - but I don't know if that's practical to do on his chassis.

 

tach

Attachments

Images (1)
  • tach

Stan,


Thanks for your reply.  I have to check again, but I think the 3 wires running from the tach reader are as isolated from the motor housing and its leads as you can get.  Even if they weren't, I don't see how the "noise" from the motor leads has any bearing on the surging issue.  If running at normal fixed operating voltages and that scenario you presented were true, then my inclination is that the result would be excessive surging regardless of the set speed of the locomotive, would it not?

Originally Posted by John Korling:
... I don't see how the "noise" from the motor leads has any bearing on the surging issue.  If running at normal fixed operating voltages and that scenario you presented were true, then my inclination is that the result would be excessive surging regardless of the set speed of the locomotive, would it not?

John, that's clear thinking for sure.  But my understanding from your first post is the engine does surge regardless of speed when loaded.  Apparently the surging is just more subtle at faster speeds.

 

The problem only appears when loaded. When loaded, the engine's lights don't get brighter, the speaker sounds don't get louder, etc.  What changes is more current is flowing to the motor - and that current flows as high-frequency pulses due to how the PS2 electronics drives the motor.  I was supposing that these pulses are coupling back into the tach circuit as "noise".  Extra tach pulses would report a faster speed than actual, the speed control would reduce the motor current to slow down, the reduced current would slow the motor and reduce the "noise", without the extra pulses, the tach would under-report and the cycle repeats.  And if the speed is varying, say, 5 MPH, this would be more subtle at 50 MPH than 8 MPH. Again, this is just a hypothesis based on limited observations.

 

So is there a fold-the-tent threshold where you'll just live with it or send it in for repair, or are you on a mission to get to the bottom of this?  This is a most interesting puzzle.

Stan,  The problem is your honing in a potential cause before dividing the problem.  You would be amazed at the way various wire bundles are put together.  Only the motor leads and speaker leads have twisted wires.  Only the Loco sounds use a capacitor across the motor.

 

By all means John can try it, but by removing all the other harness, the more likely causes of pinched wires and grounds are removed, along with any noise other than the motor.  So if it still acts up there are ony a few possible problems.  Mechanical or electrical.  The electrical are tach reader, motor and processor board.  The tach reader swap is an easy inexpensive try. 

 

Remember some of these wires share double duty, so a fault in the volume pot or a light, or a smoke motor can be reflected else where.  G

I had a RailKing SD70ACE with this problem out of the box.  Being somewhat, shall we say, "unskilled" in the art of train repair/trouble shooting, I made the bold call to lube the gears a little.  I figured it sat on a shelf for at least a year and a half, so it might be a little dry.  It was, so a greased the gears a little and started running it.  It was still a little jerky, but seemed a little better, so I kept running it at higher speeds for about 15 minutes or so.  After a while, it smoothed out across the entire speed range.  It now pulls steady at 3 SMPH without any hesitation at all.  I did nothing else to it; maybe I just got stupid-lucky, but I thought I'd throw it out here just for fun

 

-Eric

Post
The DCS Forum is sponsored by

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

×
×
×
×
Link copied to your clipboard.
×
×