 Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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Hi all! I have a Class 94 tank engine from set 29721, which is my first MFX loco complementing some old Delta and FX stock. I use the MS2 that came with the set and have had a problem develop: when running the loco at speeds of above 6 bars on the controller, it starts to surge i.e. suddenly go to full speed for half a second then back down to the commanded speed for half a second multiple times, with a surging lasting up to 2-3 seconds. If it goes on for longer than that, the loco stops but the sound continues. I then have to either reverse direction or press the stop button before I can continue. At 6 bars or below, the loco runs more stably but occasionally drops speed slightly for a few seconds. My old fx Class 03 (37952) (the only other loco I am running at the moment) has none of these issues and runs smoothly. My C-Track is a bit greasy as I think I might have over-oiled my locos and rolling stock  and I am running a mixture of track from 2004/5 and 2020. I am now running a Trix track-cleaning car (24050) that seems to be picking up the worst of it, but the surging issue remains. I did drop the MS2 a little bit onto a carpeted floor and I have some issues with that, but since the other loco is running ok, I am unsure whether this is the culprit. Does anyone have any thoughts or experience of this? I want to buy a couple more MFX locos but I am reluctant to as I want to make sure this is sorted out first so I don't damage anything. Thanks!
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Joined: 07/01/2015(UTC) Posts: 729 Location: England, Suffolk
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Out of curiosity is there a serial number under the loco?
A small rectangular sticker with a first letter and seven to eight digits afterwards? Can't find which loco it actually is on ebay.
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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 Joined: 04/02/2011(UTC) Posts: 3,563 Location: Paris, France
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Hi
It may indicate the decoder has a problem in the motor drive transistors
If it was an oily track issue the loco would stop
Cheers
Jean |
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Joined: 07/01/2015(UTC) Posts: 729 Location: England, Suffolk
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thank you for the S/N. It isn't an mfx C-Sine motor and this is good. I had an mfx locomotive that behaved like yours and M had to change the PCB controlling the motor. But as JohnjeanB says it could be the decoder having problems. The Marklin spare part number for the decoder is '290 819' and it is not available on M's website. You could try with one of the new Marklin sound decoders though, as long as it is a 21 pin decoder.
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 Joined: 21/01/2004(UTC) Posts: 1,274
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If you mention overoiling in combination with a BR94 I have to think of the oil-in-motor issue. Although the symptoms do not entirely correspond to what I had, it could be related. I just put too much grease into the wormwheel assembly, and my loco had a tendancy to stutter, due to oil/grease leaking on the motor brushes (but also keep sound/light). The stutter was caused by the electronics going into current limit protection, because the oil had the motor draw too much current. If you have a DC power supply to test the motor without decoder you can maybe check whether the motor is ok or not. My supply went up to 3A (while normally it should only be ~0.1A or so). See here: https://www.marklin-user...lin-BR94-5-18--cat-37160I doubt the MS2 is to blame. Bert
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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I spotted the grease in the worm gear housing and I haven't put any additional lubricant in there as I know not to mix oil and grease in a gearbox (previous experience!). The grease appeared to have been pushed away from the worm gear though so I will get back to the loco later to see if I can push it back in. I will have a quick look at the motor and decoder board for contamination as well. Electronics are definitely not my forte but I am ok with replacing PCBs as long as there is no soldering. I might try contacting Marklin directly as well as I only bought the set in November last year so it might still be in warranty. Thanks all for the help and advice! I love specialised forums like this. 
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Joined: 21/01/2004(UTC) Posts: 1,274
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How does it run with the shell removed? Still the same surging behaviour? How does the decoder look? Normal/burned? Is it hot? Is it plugged in OK?
Maybe the loco is switching between analog mode and digital mode for some reason (due to MS2 malfunction)? If you run only digital, you can try to disable analog mode I think by setting certain CVs. Not sure whether you can do it with the MS2 though. I had to do a similar thing once with my Brawa V36 that starting running off at full speed from time to time on its own. After disabling analog support that issue was resolved.
Bert
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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Sorry to keep you on tenterhooks, I haven't managed to run anything since I posted yesterday due to work and family stuff. I will get back on it tomorrow and I will check whether the I can disable analog mode in the MS2 as well, thanks for suggesting that!
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Joined: 04/02/2011(UTC) Posts: 3,563 Location: Paris, France
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Hi
Make also sure that the loco (being a mutilprotocol one MFX, DCC, MM2) does not receive contradicting orders from your Central Station (may be also MFX, DCC, MM2?).
Easy to check: disable all protocols but the one you use (MFX?) does the strange behavior continues?
I know it seems strange but it is possible to have an MFX link with a loco while have a 2nd link with the same loco on DCC with different orders on speed and direction. Protocol arbitration works good on the loco when the current pick-up is perfect. I made some funny discoveries while testing a LokSound 5 and a CS3
Cheers
Jean
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Joined: 23/04/2019(UTC)
Posts: 497
Location: Copenhagen, Denmark
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As I read it he only has the MS2 and no other controller that can interfere with the running of the trains? I would first try and delete the loco from the MS2 and then register it (automatically) again, and even do a reset of the decoder, which will make it register again to see if this does anything.
CV50 controls the protocols. If there is a manual with the locomotive it should be on one of the last pages, just before maintenance and spare parts. CV50 value 15 enables all protocols, value 8 only enables mfx, value 12 only mfx and DCC. The other protocols are analog AC and analog DC.
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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Thanks again for all the helpful suggestions! I just had a chance to run the loco with the body off and I'm still stumped. I think there is some issue with the drive i.e. either the motor & flywheel, gearbox, the electronic drive, or some combination, but I cannot pinpoint the problem at all. This is what I have found:
1) There is some oily fluid (possibly oil from the 3rd axle) at the interface between the 3rd rail pick-up shoe and its connection to the loco body. I gave this a clean but it had no impact on the running problem.
2) There does not appear to be any damage or evidence of overheating of the circuitry and to my untrained eye the soldering looks ok.
3) There appears to be a vent at the base of the worm-drive gearbox from which about 1/2cc of grey grease had been ejected. On viewing the worm-gear through the port in the top of the gearbox, it appeared to be dry. I added some grease to the worm-gear (about 1/2cc) but this had no impact either.
4) Running the loco with the body off clearly demonstrated that the motor vibrates significantly when under any load, albeit for irregular periods and intervals. Any attempt to run it at high speed causes it to shut down within a couple of seconds.
5) Resetting the loco via the MS2, resetting the MS2 and changing the loco protocol to MFX-only has had no impact on the running problem. As Copenhagen observed, I do not have a CS, I only have a 2.7m x 1.2m temporary layout in my 'home office' for now.
As I said above, I am stumped and I sadly have no expertise or experience in electronic drives. The loco is within warranty so I think I will take my findings to Märklin to see what they can suggest. Thanks again for your help and advice!
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Joined: 23/04/2019(UTC)
Posts: 497
Location: Copenhagen, Denmark
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The dealer or Maerklin should fix or replace it for free if it's still under warranty.
I've had a local workshop replace a motor in a 39677 locomotive. It would run fine at half speed and up to about 75% speed. At faster speed it would stop or slow down intermittantly. The motor was faulty, it would draw too much power at all speeds (which could be monitored from the control station, a CS3) and eventually overheat becoming almost too hot to touch. I didn't try to get it fixed by the dealer because of lockdown and impatience.
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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Originally Posted by: Copenhagen  The dealer or Maerklin should fix or replace it for free if it's still under warranty. That's what I am hoping. I bought the set from a dealer in Germany so it will need to travel overseas anyway as I don't think there is an authorised servicing dealer in the UK, so I will try Märklin in Göppingen. Got to find the invoice now!
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Joined: 23/07/2014(UTC) Posts: 8,473 Location: ENGLAND, Didcot
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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Originally Posted by: kiwiAlan Wow! Is this peculiar to this particular loco or am I going to need to seriously research all my upcoming purchases!?
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Joined: 23/04/2019(UTC)
Posts: 497
Location: Copenhagen, Denmark
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Nayfun83, if there was a general quality issue with Märklin locomotives you'd see lots of threads about it. So I wouldn't worry about future purchases. The problem is, seemingly, related to a specific model and not Märklin products in general.
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Joined: 26/01/2021(UTC) Posts: 21 Location: North Somerset
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That's good to hear, thanks!
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Joined: 23/07/2014(UTC) Posts: 8,473 Location: ENGLAND, Didcot
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Originally Posted by: nayfun83 Originally Posted by: kiwiAlan Wow! Is this peculiar to this particular loco or am I going to need to seriously research all my upcoming purchases!? I found all those by searching the forum for your start set catalogue number. As my first post in this thread said (although i got the loco class wrong because I didn't look it up) there does appear to be a manufacturing problem with this particular loco.
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