Piko mogul not behaving

kim

kim

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Blackpoo
I bought this a while ago from Darren at Top Slots for very little money because it stutters when setting off with front and back lights flashing and then stops for no apparent reason. On taking the bottom gearbox cover off the loco I found 2 teeth missing from the cog on the front driver axle and the same on the intermediate gear, replacements ordered. Appreciating that the flashing lights suggests a dcc problem I thought I'd see what fixing the drive brought about. Anyway, new bits duly arrived and fitted today, well lubed and loco put together again, guess what, still stutters!
Altered the speed steps and found that on 128 steps and given full throttle the loco moves off - a bit sharpish - but with no stutter and then runs perfectly in both forward and reverse, front and back lights flash a couple of times and then behave. The loco will slow down to a crawl and behave but once stopped it needs to be off at full speed.
Thoughts please.
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
23,464
487
Tamworth, Staffs.
Normal things:
Check pickups, brushes, wheel-backs (if Piko does it that way?), check continuity down each side of loco..

Check CV settings for start voltage, perhaps raise this a little? - As in the starting voltage for 'step 1'.
 
kim

kim

retired at last
27 Apr 2015
712
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68
Blackpoo
Normal things:
Check pickups, brushes, wheel-backs (if Piko does it that way?), check continuity down each side of loco..

Check CV settings for start voltage, perhaps raise this a little? - As in the starting voltage for 'step 1'.
No brushes on this Phil, brass strips picking up from bushes on axles 1 and 3 plus skates and I've put pick up from the tender as well, wheel backs like brand new, which basically it is!
I have a problem with cv's, double dutch to me.
 
kim

kim

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Measure the current drawn and see if it is abnormal, sounds like a mechanical friction problem.

Greg
I shall be stripping it down again today Greg and starting from scratch. The wheels do rotate by hand but it could be smoother. After reading Phils response I did some reading on Piko re cv's and I will be diving in and looking to return everything to factory defaults - cv 8 set to 8.
 
kim

kim

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Well, this has been a day of trial and error. Put the mogul and tender on the massoth programming track and did the factory reset to find that nothing responded afterwards. After much messing about I disconnected the 1200z and connected the lgb programming unit, as expected it told me that it was not an lgb chip but it did allow me to program the loco after doing a factory reset. I then connected the 1200z and readdressed the loco and all was fine, everything worked. The mogul went on the track and everything seemed great until a few minutes later back to as was. The amp read out on the handset was jumping between .1 and .4 amps which pointed me to the motor so then stripped the loco down again and took the motor out and did what I should have done last time, gave the motor a spin by hand. The motor has a square commutator, it is lumpy and no wonder the loco behaved as it did. Off to top slots tomorrow and hopefully that's the end of this saga.
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
23,464
487
Tamworth, Staffs.
Motor - QED??

Obvious:

QED = Quite Easily Damaged
;):giggle::giggle:
 
Greg Elmassian

Greg Elmassian

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That's good Phil!, just trying to underscore that when you have issues, take some measurements first, erratic current draw will point you in a direction early... if the loco is not moving, like on it's back, pretty much has to be motor... moving it could be pickups, but too much current is a dead giveaway, mild short or motor issues.

Greg
 
kim

kim

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Well, it aint the motor. At Top Slots yesterday to buy a new motor only to find that Piko motors are lumpy so I thought 'to hell with this' and to remove any thought of mechanical issues I bought a complete new drive block which for £78.99 aint a bad deal for motor, wheels, intermediate gears, gear box, crank pins etc!
Rebuilt the loco, on the track and...........you guessed it, stuttering at low revs with head and reverse lights flashing. Grrrrrrrr. After some messing around switched the track onto dc and the loco runs as sweet as a nut right through the speed range, so it has to be the dcc board. The flashing lights did point to this originally hence the reset to factory cv values so back to Phils suggestion of starting voltage but perhaps an email to Piko technical guys as well.
I will report back........
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
23,464
487
Tamworth, Staffs.
Can you alter the frequency of the PWM output of the decoder?

Turn OFF all lights, smoke, anything else that draws current.. I wonder if a short (could be intermittent) on something is causing the decoder to shutdown?
 
kim

kim

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27 Apr 2015
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Blackpoo
Can you alter the frequency of the PWM output of the decoder?

Turn OFF all lights, smoke, anything else that draws current.. I wonder if a short (could be intermittent) on something is causing the decoder to shutdown?
Way beyond me that one Phil but I do agree with you that the decoder is the culprit. Interestingly - or not - the Piko spares list for this loco is showing both the motor and decoder as not available, I have emailed the Piko tech lads so might get something back in a week or three. But in the meantime I'll have a tinker!
 
kim

kim

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Well, tinkering has been done using the good old 55045 mts pc decoder on an old windows xp laptop and the motor pulse has been changed from 0 to 1 and starting voltage raised to 10v and we have success, kind of! I have 2 circuits on the rr and after changing the track voltage to 18v the loco is now very happy on the outer circuit with 9 and 10 foot curves and only 2 radius 5 lgb points that are used on the straight. The inner circuit is a different story with 8 foot curves and Aristo 10 foot points, the loco stops and judders at a few places, on a curve from the diverging track on a point, an 8 foot curve a few feet further along and on diverging routes from points a few feet further along. A Piko camel back with exactly the same electronics and chassis sails through with no problem, as do all the lgb loco's.
Thanks to Phil and Greg for their input and if anyone else has any ideas please dive in! Pics below of the troublesome areas, excuse the glare from the super clean brass!

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Last edited:
John S

John S

Registered
5 Nov 2017
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Exeter, Devon, UK
Just out of curiosity and for research purposes, have you be able to determine the decoder Manufacturer?
 
kim

kim

retired at last
27 Apr 2015
712
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Blackpoo
Is it possible you have power pickup issues that only manifest on sharper curves?

Have you double checked all power pickup points?

(how many are there?)

Greg
Been out with the meter Greg and no issues, only have one feed but it's aristo track and all joints are bolted and the lgb switches are hillman clamped. I've decided to massoth xls this loco to get rid of the problem and I will still be quids in, loco cost £100, new chassis £79, xls £180ish and I will have a spare chassis. As stated, all other loco's are fine and run great, currently got my mikado out.

121619_fdf8b9ead5c73eba9a7ec72f449c2e45.jpg
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
25,241
548
North West Norfolk
Been out with the meter Greg and no issues, only have one feed but it's aristo track and all joints are bolted and the lgb switches are hillman clamped. I've decided to massoth xls this loco to get rid of the problem and I will still be quids in, loco cost £100, new chassis £79, xls £180ish and I will have a spare chassis. As stated, all other loco's are fine and run great, currently got my mikado out.

View attachment 251228
loco power pickup was what I think Greg meant :oops:
 
kim

kim

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loco power pickup was what I think Greg meant :oops:
Oops, misread that one! The loco pickups are fine and I have track feed from the tender wheels as well. I would appear to have fixed the problem, noted that the mikado didn't like the rad 5 switch shown in picture 1 so I changed it and sorted the levelling out as well - a job I've meant to do for a while - and hey presto, gave the mogul a slow run and it's still chugging away quite happily. Had a good look at the switch and can't see anything wrong on it and there's no short on resistance test. So hopefully that's it and thanks again for the advice that has been given!

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