Lionel Main Line Color Position Signal #72-4101-250

Can't find anything by Lionel with that number?

That was the number on the instruction book.

The number on the box is 6-24101 Lionel Mainline Color Position Signal

Check this link Mainline Color Position Signal

Note the last sentence, sounds like a bad pot  or connection.

Dave

Hi Dave,

Seems like its been a problem for a long time. I sent an E-Mail to Lionel service and will wait for a reply. Seems like its not my day for signals. I have 2 Z Stuff signals I have to return the yellow lights  do not work goes from Reg to nothing then to green. I called Z Stuff and they will either repair them or replace them, can't ask for better service.

I would try turning that adjustment screw back and forth a few times. The potentiometer's wiper may not be making good contact - if that's what is in there.

Dave

I did that already, it was no help. I tried it at all positions, 1 time it turned green when I pressed the screw but it never happened again.

The 6-24101 is the number forum members will need to figure out what you have. If you have adjusted the 153 properly and also the adjustment screw on the signal it looks like that is about it for setup. My guess would be that something is not yet adjusted properly, I think it would be unusual that 3 of the same devices were all defective? But, I suppose stranger things have happened and it's possible? 

I don't have one to experiment with, but maybe someone here that does will stop by and provide further assistance.

Also, sometimes things like this take a little patience and precise fiddling before they will cooperate.

There could be a problem with the design or manufacturing that causes the problem.  The wiring is straight forward and the light does turn from green to red when the train passes. I tested it using both the 153C and 153IR with the same results. I have tried the adjustment screw with the full range of movement. I hope to get a reply to my E-Mail to Lionel, if not I will try calling the service department.

Lionel is usually pretty good about replying to emails, but calling them is good too. Good luck and I hope they have some good news for you.

I will update the subject when I hear from them. With all 3 having the same problem I would guess it is a design problem.

Question, do you have a isolation track section? If so have you checked the wiring on that?

Hi Mike,

 No I don't have an isolation track. I use the #153 IR and wired it as per the instructions. When that did not work I used the #153C that came with the lights, followed the wiring diagram and had the same results. Changes from Green to Red to Yellow and never goes back to Green. 

Going to be a stupid answer if your loop of track is small or your train goes to fast the signal not having time to reset back to green. You have to give it at least one min to go back to green. I have mth B&O signals does same thing because my loop is small and some of my trains run faster then others and does not give my signal a chance to turn green til train back to it again.  

I gave it 10 minutes, once it turns yellow it stays yellow until I remove power then it resets to Green. Turns Red when the train contacts the #153C or @153 IR, turns Yellow and remains Yellow.

bobnj1 posted:

I will update the subject when I hear from them. With all 3 having the same problem I would guess it is a design problem.

Did you ever get a reply from Lionel ???

Dave

No, I never heard from Lionel. I had a problem with an MTH Gate as well, MTH called back but do not have the gate in stock and there is not an authorized service center in my area, so i am stuck with a gate that don't work. I think I am better off with all my accessories from the 1950's that still work. I have an MTH Gas Station that don't work and won 2 new in the box Gas stations on E-Bay I had to return because they did not work. My MTH car wash no longer has sound and my MTH Dispatching board is hit and miss. Seems like both major manufacturers have a Q.C. problem.

What are you planning to do with the Lionel MLCP signals?

Although I am not interested in that type of signal, I would like to see the insides. I doubt they are unfixable.

Dave

I plan on using them in my yard, they do change from yellow to red and back to yellow. I have lived for 60 plus years with green and red I can live with yellow and red. The Z stuff signals were repaired and are working fine.

Sounds good.

Dave

I realize I'm a late comer to this thread but was curious if it was ever resolved.  I purchased the Lionel Color Position Signal new quite a few years ago and it sat in the sealed box until yesterday.  Mine has the exact same problem Bob described. Exact.

I ran the pot back and forth many times to clear the contact surface, ran the voltage max to min, gave it hours to react , tried different wiring arrangements but it remained stuck on orange.  I can add that on setup (page 5 of the manual), the signal did not follow the manual's description.

I can't use as is so I'm going to tear into it.    I'll be better off with old school no-electronics operation.

Frank

Frank, post some pictures of the insides, board, etc. if you can, before disconnecting everything.

Dave

Will do.

@Dtrainmaster posted:

Frank, post some pictures of the insides, board, etc. if you can, before disconnecting everything.

If you post a few clear photos top/bottom the circuit should be "simple" enough that one of us should be able to draw out the schematic and put this issue to rest... for the common good of course. 

Sorry for the delay. I disassembled the signal, removed the PCB, protective tape, epoxy and took 3 close up shots.  Powered up, the failure remained unchanged.  A few observations.....the soldering appears to been done manually and very poorly at that.  A solder bridge could exist.  On the bottom of the PCB,  several traces run under a dot of formidable epoxy.  I'm assuming the control circuit is being hidden for there is no other IC on the board.

There is a PCB in the head but that looks to be a component-less connection point for the LED's.   I found the wiring to be ....

yel & blk   green leds, red & grn  red leds, red & wht yellow leds.  For my goal of old school waiting, I tied the yel and red together to form a common and added a 1k current limiter for the connection to blk, grn, wht to operate the signal.

Provided I'm not viol;eating any forum rules, I would be pleased too mail the PCB to the preceding member.

I'm not sure how far the troubleshooting will go but at least Bob P. will know he is not alone.

Good luck, Frank

Yes Frank, that black epoxy is no doubt the brain, i.e., no replaceable decision-making components like transistors or ICs. But that doesn't mean that there isn't something fixable in the simple circuit.

Dave

Thank you @Frankgb for dissecting one of these signals.  I have purchased some that didn't signal properly but haven't taken the time to investigate.  I appreciate that you removed the circuit board and shared pics.  Please elaborate on what it took to remove and if it can go back together successfully.

Now for fixing.  It looks like it is nothing but 9 resistors, 4 capacitors, a potentiometer, some diodes and a single transistor (Q1).  Since these seem to show up new as broken then I doubt it is caused by a component failure but rather by production.  Lights illuminate for the most part but don't change as expected.  What determines that is the variable resistor and the transistor.  You said the solder looks sloppy so I see a couple of spots where the solder may have flowed/wicked over to another node.    See marked up photo below.  Please check resistance to see if the nodes are shorted.  Left arrow is Potentiometer to R8 and the right arrow is Potentiometer to R5. 

@Frankgb posted:

...

Provided I'm not viol;eating any forum rules, I would be pleased too mail the PCB to the preceding member.

If you're referring to me, I did not see an email in your profile (I don't post mine either) so if you send an email to

(deleted)

I will send you my mailing address

As others noted that formidable dot of black epoxy is indeed the brains.  That's known as COB (Chip-On-Board) packaging where the IC chip is mounted right on the board.  It is obviously not user-serviceable!

If you don't make any progress with the tips others are giving, I would be happy to figure out the schematic and post it here on OGR for posterity.  It is quite possible it is not the formidable blob at fault in which case I can probably fix it and mail it back to you if you still want it!

@Steims posted:

... What determines that is the variable resistor and the transistor.

....

Right.  If you look at the discussion in another forum that @Dtrainmaster posted 5 years ago at top of this thread some of the guys come to the same conclusion.  But the thread went cold without confirmation that the 100K variable resistor was indeed the culprit.  Of course the trimpot itself is maybe 25 cents but with minimum orders, shipping, etc. it can change one's perspective!

Somebody is not afraid of a challenge! I did reply with my email.  When you receive the PCB, no need to return.  I'm wiring the signal's LEDs to my digital system.

It's difficult to see if circuit points are intentionally connected through the trace or solder bridge.  If you draw out a schematic, I guess you can tell if its designed that way or not. I found that R8 is shorted to that pot.  

Thanks for the "chip on board" identification.  I thought it was a security measure.  Lower cost manufacturing makes more sense. As wikipedia stated "used on low end devices".

Happy Hunting, Frank

@Frankgb posted:

...

Happy Hunting, Frank

Address sent.  I just hope it's not a snipe hunt!

Good luck Stan!  Thanks for taking an interest and sharing the results when you get them.  Frank, how much effort to remove and reinstall the boards?  Are they only held in by RTV/silicon?  I was thinking there was a couple of rivets on the bottom.  

Yes, the riveted plate on the bottom of the casting holds the board in.  Each rivets starts out as a boss that is part of the aluminum casting and swaged to form a mushroom head. Once you drill the 4 out, an alternate means is needed to secure the plate.  The plate is inset so one could epoxy or drill & tap for  small machine screws

To remove, I started out with 1/16" bit to drill a center hole and followed up with a 1/8 to cut the mushroom off. Don't go too far.

The board will slide out with a tug. There is sticky tape to keep the PCB from shorting on the case.

Hope this helps, Frank

\

As an alternative to repairing the 24101, Rod Miller @romiller49 removed the internal Lionel circuit board and went with an external board.  Here is a link:

https://ogrforum.com/...onel-mainline-signal

@stan2004 posted:

Address sent.  I just hope it's not a snipe hunt!

Stan, interested in seeing the difference between this one and MTH's basic layout of their signals. I don't see a V regulator, unless they're using that zener, MTH used a dedicated chip.
I anxiously await your dissection of the circuit, provided the blob is not hiding too many secrets. A shame you don't have a working unit to take readings from.

Dave

I literally just brought it in from the mailbox!  Thanks to Frank.

Yes, at first glance it looks like there's a zener.  My intent to get to the bottom of this one way or the other.  This has been going on for too long!

Go Stan Go!!

I hope it is as simple as that possible solder bridge between R8 and Potentiometer.  Maybe that shunt is negating the pot resistance to the circuit creating a “no delay” situation.  That could prevent the Yellow light from illuminating and only getting Red to Green.  The fix would be simple.  

Well, there's no joy in Mudville.

But to review the situation.  From the manual:

This signal has a somewhat unusual hookup for a 3-wire device.  Two wires (Yellow and Black) go to AC Accessory Power (12-18V AC).  The 3rd wire (Green) is normally connected to Yellow (AC hot) when no train is present.  The signal should be green when untriggered.  So you disconnect Green from Yellow and the signal should turn Red.  This is backwards from the insulated-rail method but that's a separate discussion that is interesting but I think not germane to the matter at hand.

Anyway, you re-connect Green to Yellow (train passes) and signal turns Yellow...then delay...then Green.  BUT. As reported, the signal never turns to Green.  It will turn to Red when triggered.  It will turn back to Yellow when un-triggered...but again never to Green no matter the delay.  Lather, rinse, repeat.

I cannot find any assembly errors.  It is/was indeed sloppy soldering but I could not find any solder shorts, bridges, etc.  The 100K trimpot is functional.  The only other interesting behavior is when initially powering up in the untriggered condition, it will sometimes go right to Yellow and of course just stay at Yellow; it then just goes between Yellow and Red when triggering or untriggering.

I have fired up the oscilloscope to see what the analog time delay voltage signal is doing (presumably controlled by the trimpot).  It would be nice to have a working board to compare to, but one must make do with what one has!

From what I can tell, the board itself is No Longer Available from Lionel.  Plus, I was struck by how small it is.  Yes, it has to fit in the base of the signal...but it would still be difficult for the average guy to replace with tiny wires going everywhere connecting to random locations on the circuit board...some wires connecting on top, others on bottom.

I sketched out a schematic which I'll post later though it really doesn't tell you much since all the magic is going on under the Blob which is of course the end-of-the-road (aka dead-end).

Any comments welcomed...especially if you too have a broken CPS.  Did it "fail" as described above?  Was it something that happened over time or out-of-the-box?  I have my suspicion about what causes this but all observations add to the collective knowledge.  Remember guys, this is a discussion forum for the common good; I just find this aspect of the hobby interesting and an end-in-itself!

Stan, can you get a reading on that transistor, is it changing at all during the transition?

I'm wondering about a Cap not charging completely to end the time cycle. Of course, the Blob may be up to no good also.

Dave

The only transistor I can see (Q1) appears to simply buffer the zener-diode regulator and does not affect the timing (capacitor charging/discharging).

I believe the key signal is the node identified above.  This is where the 100K Ohm trimpot meets a large capacitor (100 uF) which undoubtedly adjusts the yellow-to-green time delay. That is, the RC time-constant is on the order of seconds which is as expected. This signal does not change much when triggered or untriggered. The Blob is responding to the trigger signal since the LEDs toggle between red and yellow.  It's just the Blob does not seem to charge/discharge the timing capacitor via the trimpot.  The trimpot and resistors measure out OK.  The only other replaceable component in the timing circuit is the capacitor which would be a shot in the dark but easy enough to try...