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Offline asterduc  
#1 Posted : 31 October 2022 13:17:28(UTC)
asterduc

Belgium   
Joined: 31/10/2022(UTC)
Posts: 3
Location: Antwerp
Hello Marklin Community,
been here many times as a guest, however never got active ... untill now.

I have an original ICE Experimental 3371 that is no longer working properly.
There are a lot of postings to convert this elegant train into digital but none on keeping it analog.

The electronics on my 3371 are malfunctioning and I have to decide whether to repair the board or to convert it into digital.
My preference goes for the analog repair because I feel that it runs smooth enough with the Faulhaber motors and I would use it analog over the cantenary supply.
Understand that I love to keep things original too.

Concerning the problem with the electronics:
The trains starts well but after less than a minute the motors start to slow down untill they stop completely (also without the transmissions connected).
I want to repair the board, but can't find any schematic. Reverse engineering is possible, takes a lot of time.
Measuring all components is another option, takes time and effort too.

I would be very very thankfull if someone could provide me with an electrical drawing of this main board. The number on the board is 16663 (1985 build).
Or any feedback from experience would be welcome too.

My first guess would be that the power transistors BD439 don't do a proper job as they run pretty hot rapidly. Motor current is 0.6A / each.
Another suspicion goes to the capacitors since they may have lost their value after 37 years.
I measured the output signal to the motors and that did not really look like a DC voltage, the sinus got sharp pikes at the time that the motor stopt. Voltage was still there but there was no current.

Any advice or thoughts are appreciated.

3371 pcb.jpg

3371 measurement.jpg

3371 measurement1.jpg








thanks 1 user liked this useful post by asterduc
Offline kiwiAlan  
#2 Posted : 31 October 2022 13:38:35(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 7,395
Location: ENGLAND, Didcot
I would suggest looking at the voltage across any filter electrolytics after the rectifier of the track voltage. These should be easy to identify.

You shouldn't have any sinewave across the Faulhaber motor, so I suspect the electrolytics have dried out and will need replacing. I would limit the running time until you have it repaired as you can seriously damage those motors with low frequency sinewaves like that, it can litteraly shake the windings apart.
thanks 2 users liked this useful post by kiwiAlan
Offline marklinist5999  
#3 Posted : 31 October 2022 15:31:48(UTC)
marklinist5999

United States   
Joined: 10/02/2021(UTC)
Posts: 2,030
Location: Michigan, Troy
When upgrading one of these to digital mfx, do you still need a reversing relay circuit for the lighting direction, or do the new decoders do the motor and lighting?
Offline asterduc  
#4 Posted : 31 October 2022 18:54:02(UTC)
asterduc

Belgium   
Joined: 31/10/2022(UTC)
Posts: 3
Location: Antwerp
Originally Posted by: kiwiAlan Go to Quoted Post
I would suggest looking at the voltage across any filter electrolytics after the rectifier of the track voltage. These should be easy to identify.

You shouldn't have any sinewave across the Faulhaber motor, so I suspect the electrolytics have dried out and will need replacing. I would limit the running time until you have it repaired as you can seriously damage those motors with low frequency sinewaves like that, it can litteraly shake the windings apart.


I replaced the capacitors on the entry, after the diode, but that doesn't solve the problem. The sine is still there.
Now did some minor reverse engineering on the power supply part. The 4 rectifiers are working fine, but one of the 2 capacitors does not have any voltage potential. I will have to dig somewhat further in that board layout. I suspect a shortening or heavy load in that circuit (transistor?). If I would have the board schematic, this would make live much easier Bored

You are right on saving the motors from this 100 hz sine wave, I'll do all the testing with the scope from now.




Offline 1borna  
#5 Posted : 31 October 2022 19:16:57(UTC)
1borna

Croatia   
Joined: 21/12/2012(UTC)
Posts: 1,127
Location: Hrvatska
Perhaps the scheme could be found on https://moba-hgh.de/ ?
Offline river6109  
#6 Posted : 01 November 2022 08:20:33(UTC)
river6109

Australia   
Joined: 22/01/2009(UTC)
Posts: 14,115
Location: On 1965 Märklin Boulevard just around from Roco Square
If you like to buy one, I have an analog board for both motor wagons

John

Edited by user 02 November 2022 08:23:29(UTC)  | Reason: Not specified

https://www.youtube.com/river6109
https://www.youtube.com/6109river
5 years in Destruction mode
50 years in Repairing mode
Offline DTaylor91  
#7 Posted : 02 November 2022 05:05:03(UTC)
DTaylor91


Joined: 31/08/2007(UTC)
Posts: 414
Location: Kennesaw, GA
Originally Posted by: kiwiAlan Go to Quoted Post
I would suggest looking at the voltage across any filter electrolytics after the rectifier of the track voltage. These should be easy to identify.

You shouldn't have any sinewave across the Faulhaber motor, so I suspect the electrolytics have dried out and will need replacing. I would limit the running time until you have it repaired as you can seriously damage those motors with low frequency sinewaves like that, it can litteraly shake the windings apart.


Agreed. I work on vintage audio electronics all the time. Dried-out filter caps will make your amplifier hum, which means there is a sine wave getting onto the +/- power rails. Replacing them all should be relatively cheap. Not knowing the circuit, but assuming the BD437 transistors feed current to the motor, the unexpected AC current could be making them overheat. So, after replacing the capacitors they should not get as hot. If the heat concerns you afterwards, there are many small heatsinks available for the TO220 package.

Also, since this has apparently been overheating a lot, hold the PCB up to the light and look for any discoloration due to heat. If there appear to be any "toasted" areas, especially approaching a golden-brown color, it may be necessary to take a very small Dremel tool grinding tip and remove the scorching from between traces. Many a cooked circuit board has brought an amplifier (which this circuit basically is) to its knees due to current leaking across the carbonized area. Also, it may be wise to remove the old solder from components that have gotten hot and applying fresh solder. Heat breaking/weakening solder joints can cause many issues, even if the solder joint "looks ok"

thanks 6 users liked this useful post by DTaylor91
Offline asterduc  
#8 Posted : 22 January 2023 21:27:13(UTC)
asterduc

Belgium   
Joined: 31/10/2022(UTC)
Posts: 3
Location: Antwerp
sorry for the late reaction.
Meanwhile I got it solved. I replaced the caps, measured the diodes and transistors, but didn't find any bad components.
The damage was in both motors. They started spinning, current went up and the ptc's disconnected them.
I assume that the previous owner tried to run the train with sticky oil in the transmission and destroyed the motors by doing so.

These Faulhaber motors are not easy to find and if so, then they are pretty expensive, at least for this affordable train.
I therefore replaced them by a set of new chinese brand 6pole 12V/24V DC motors.
They matched the Faulhaber's sizewise, rpm is about 30% lower which compensates somewhat for the slightly lower torque.
The ICE is now running soft and easy, especially for a full analogue.
Total repair cost is 3 euro for the caps and 9 euro for the motors, making it an incredable 12 euro BigGrin .
In return I got a wonderfull errorfree running experimental and a good lesson in 3371 practice.

Thanks all for your help.
Video:
https://photos.app.goo.gl/PD7UfNoWzUqLMZi57

3371_02.jpg3371_01.jpg



thanks 5 users liked this useful post by asterduc
Offline marklinist5999  
#9 Posted : 23 January 2023 00:47:44(UTC)
marklinist5999

United States   
Joined: 10/02/2021(UTC)
Posts: 2,030
Location: Michigan, Troy
Wise and effective repair! There are Maxxon motors in various sizes, but also pricey.
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