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Offline Dave Banks  
#1 Posted : 18 August 2020 08:42:49(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.
Littfinski TT-Dec for Marklin turntable. I had one of these cause me a great headache today trying to find a short circuit on my layout. Kept tripping my Ecos. The burned section appears to be all "earth" terminals. It supplied power to my track & set locos off doing all sorts of things despite the Ecos being totally unplugged. Never seen anything like it before. It is powered via another transformer using Yellow / brown terminals. Has any one had this happen to them so I can prevent a re-occurrence. Also where to get that push pull item that holds the "L293NE" component which looks undamaged namely 72A2C4M e4 or L293NE. Looks like I will have to replace the 16 Pin DIP IC Socket Adaptor.

[img]UserPostedImage[/img]

[img]UserPostedImage[/img]

[img]UserPostedImage[/img]
D.A.Banks
Offline kiwiAlan  
#2 Posted : 18 August 2020 17:57:52(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,082
Location: ENGLAND, Didcot
Originally Posted by: Dave Banks Go to Quoted Post
Littfinski TT-Dec for Marklin turntable. I had one of these cause me a great headache today trying to find a short circuit on my layout. Kept tripping my Ecos. The burned section appears to be all "earth" terminals. It supplied power to my track & set locos off doing all sorts of things despite the Ecos being totally unplugged. Never seen anything like it before. It is powered via another transformer using Yellow / brown terminals. Has any one had this happen to them so I can prevent a re-occurrence. Also where to get that push pull item that holds the "L293NE" component which looks undamaged namely 72A2C4M e4 or L293NE. Looks like I will have to replace the 16 Pin DIP IC Socket Adaptor.


The L293 chip is a dual bridge used to drive the motor on the turntable bridge, so before doing anything else I would take the bridge off the turntable and verify that the motor is not burned out. certainly that chip looks like the bridge has got stuck or the motor has seized and the micro has left the power on to the motor.

The chip is available from element14/Farnell/Onecall/Newark/CPC (whatever they call themselves in your area) as catalogue #1467711 and they will also have the IC sockets. The first one on that list (catalogue #2672297) will be identical to the one LDT use, but I prefer the 'turned pin' style of the second one (catalogue #1023039). Don't worry if the pictures don't look right for the actual one you have, they use generic pictures for the range.

I would also take out the microprocessor (the chip with the sticker on top with the black dot on it) and power up the board once you have the faulty chip removed, to see if the rectifier diodes on the input power have done something strange. It should have been protected by the fuse on the input (MF1 when you look at the parts layout diagram, just above where you connect the power from the transformer. The rectifier is the circular block just above that (GL1). Find a voltmeter and measure the voltage across C1 just above that and it should be around 20-25V (mine is 23.5 with 16VAC supply). Also check the voltage at the 7805 regulator mounted on the heat sink (the left hand device when looking from the terminals). One side should have similar voltage as C1 and the other side should be 5V +/- 0.25V. The centre pin is ground. The harder one to measure is the voltage on the LM317 (the other device on the heat sink). The centre pin should be around 18V. This is used as the supply to the L293.

If these all look OK then it may just be the chip that has died.
thanks 1 user liked this useful post by kiwiAlan
Offline Dave Banks  
#3 Posted : 19 August 2020 00:13:42(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.

Hello Alan,many thanks for your reply. I can manage a few of your requests as electronics is not my forte. The only damage visible is the burned bracket that holds the L293NE chip. The chip shown no signs on the outside of any damage. Neither does the big one with the sticker. I can see i am going to have fun trying to remove that holder. I will check the bridge motor operation & report back. At the time this happened the turntable was not in operation but yes connected. When the Ecos showed the fault I applied the ohm meter to the tracks & it did indeed show a closed circuit. For 17 yrs this track has been down so I had to look for the obvious being a derailed item of rolling stock or something metallic that has fallen off causing the short. Depressing the go button gave me a brief harmonic sound emanating from the track somewhere. Over the past week if I bumped the table I got the green light & no problems for the rest of the day. So yes now that this has happened I wonder if it was the issue or have I inadvertently set of a chain of events. The fitting of the Littfinski decoder was the last thing I did back in March if this year & it worked well up to yesterday Cursing. I will report back as I go. The company you suggested for parts purchase want one to buy in bulk only Angry.









D.A.Banks
Offline ixldoc  
#4 Posted : 19 August 2020 00:42:53(UTC)
ixldoc

Australia   
Joined: 18/11/2015(UTC)
Posts: 220
Location: Brisbane,Australia
Hi Dave,
Both Jaycar and Altronics list an L293D motor drive 16 pin IC in their catalogues. Make sure they are pin for pin compatible. They will also have the DIL socket if required. Worth a look.
A desolder gun would get the socket out easily,but if you don't have one a solder sucker is the next best bet. After that comes braid,with which I have had variable results.
Good luck!
Howard.
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Offline Dave Banks  
#5 Posted : 19 August 2020 01:06:31(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.
Morning Dr Howard, The one your suggesting L293D is easily available. I did look at Jaycar & they did not have this one #L293NE. I got the socket ordered from Ebay posted for $4.50. The other companies want me to order bulk @ $5.90 each. I tested the Turntable & it operated via the manually controller perfectly. It really has got me going as to why that happened. Also powering the whole layout via a #6003 transformer is alarming especially when you need to figure out why your having power to your layout where none should be present & the few seconds it takes you to work out what has happened could destroy a lot of sensitive electronics connected to track power only Confused. i have also been told that the brackets themselves are part of the problem. I have been told I am better off soldering the component directly to the board. It looks like my bracket / component did not have a good contact so its possible arching occurred at those ground points melting the holder. So for those who have one you might want to pull these off & clean any oxidization that may occur on the legs of the component. At this point this is all just theory on my behalf Confused.

Edited by user 19 August 2020 10:30:04(UTC)  | Reason: Not specified

D.A.Banks
thanks 2 users liked this useful post by Dave Banks
Offline kiwiAlan  
#6 Posted : 19 August 2020 15:34:29(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,082
Location: ENGLAND, Didcot
The best way to remove the socket is to remove the chip, (if you think it is worth saving) and then using side cutters just keep removing plastic from the socket. Then using a soldering iron pull the pins out one by one, then suck the solder out of the holes. It is the PCB you are trying to save, not the chip or socket.
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Offline Dave Banks  
#7 Posted : 20 August 2020 00:28:30(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.
Hello Alan,I never knew what an epic battle I was about to take on in removing that bracket. Long story short I took it to our local electronics company down the road & he confirmed he would have to order that chip. He also suggested I never fit a bracket as they were notorious for this kind of problem or lack of 100% connectivity hence my issue. He said he would remove & refit the chip I had directly to the board for $30.00. I said I would like to do this myself. It looked easy enough. Main reason I did not take up his offer was I have a bracket already on the way & if the chip is a no go I could remove it easily & replace it. How wrong I was. I took ages to remove. I broke it off the board easily enough & the six outer pins either side of center were not too much drama in remove the remaining broken legs. However the 4 inner ones turned out to be a real drama. It appears due to the extreme heat the pins had welded themselves into the holes. Lot if heat & pushing & prodding would not dislodge them. In the end I resorted to drill them out with the smallest drill bit I had. I think i have been successful but who know if the heat has done any damage to the tracks leading to the holes. I await the bracket & will go from there. Should have let the electronics guy take it out for me in hindsight. Silly male pride on my side or just me being a tight arse has now landed me in this situation Blink

[img]UserPostedImage[/img]

[img]UserPostedImage[/img]
D.A.Banks
Offline applor  
#8 Posted : 20 August 2020 04:27:33(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,653
Location: Brisbane, Queensland
It sounds like you've wired the turntable's rail and centre stud circuits (from the LDT-TT terminals via the ribbon cable) to the TT transformer rather than your Ecos.
Either as the turntable rotated or when you applied power (depending on the bridge position) the centre stud bumper/connector at the end of the turntable bridged the TT transformer to your layout, feeding it's ~19v power to your main layout.
The centre bumper can also touch the rail contacts and vice versa.

I did a similar thing by accident with mine.
I had correctly isolated the turntable track by removing the rail tabs and the centre stud bumper however I forgot to wire the turntables track feed to the CS2.
So my short was instead triggered by driving a loco onto the turntable resulting in the CS2 and TT transformer power/earth connections being bridged, thus blowing the CS2 power regulator.
modelling era IIIa (1951-1955) Germany
Offline Dave Banks  
#9 Posted : 20 August 2020 10:48:56(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.
Hello Eric,I connected it in the following manner. Thick Brown / Yellow from Marklin 6003. Thin Red / Brown to Ecos. Note earth Thick Brown separate to Thin brown to Ecos Remember this has been running perfectly for three months till about a week ago when the problem manifested itself. If any one sees something obvious I have missed please let me know. See below images of connections from March 2020.

[img]UserPostedImage[/img]

[img]UserPostedImage[/img]

https://www.ldt-infocenter.com/d...ssbeispiele/page_501.pdf
D.A.Banks
Offline kiwiAlan  
#10 Posted : 20 August 2020 22:55:44(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,082
Location: ENGLAND, Didcot
Originally Posted by: Dave Banks Go to Quoted Post
I broke it off the board easily enough & the six outer pins either side of center were not too much drama in remove the remaining broken legs. However the 4 inner ones turned out to be a real drama. It appears due to the extreme heat the pins had welded themselves into the holes. Lot if heat & pushing & prodding would not dislodge them. In the end I resorted to drill them out with the smallest drill bit I had. I think i have been successful but who know if the heat has done any damage to the tracks leading to the holes.


Hmm, I have a concern that drilling those holes may have produced a problem down the line. These pins are used for the ground return on the chip, as well as drawing away the heat from the chip. For both these reasons they are connected to an internal layer of copper in the PCB. It is because of this that it was taking so much heat to unsolder those pins.

Unfortunately by drilling out the pins you may have also taken out the copper barrel in the hole that provided the electrical and thermal connection to the ground plane in the PCB. I'm not sure what the best way to repair this will be.

Offline applor  
#11 Posted : 20 August 2020 23:15:20(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,653
Location: Brisbane, Queensland
Originally Posted by: Dave Banks Go to Quoted Post
Hello Eric,I connected it in the following manner. Thick Brown / Yellow from Marklin 6003. Thin Red / Brown to Ecos. Note earth Thick Brown separate to Thin brown to Ecos Remember this has been running perfectly for three months till about a week ago when the problem manifested itself. If any one sees something obvious I have missed please let me know. See below images of connections from March 2020.



Hi Dave,

Yes all your wiring looks fine (it's pretty simple after all)
Looking back at my old thread I had wired the track power to the TT trafo temporarily and had forgot to change it, so was an obvious problem.

In your case I don't know how that could have happened, only that what you describe is indicative of your TT trafo supplying power to your layout.

Can you tell us the exact events up to the failure? Was this the very first time you powered on the TT with decoder connected? Was the TT bridge aligned with a spoke track connected to the ESU power circuitry?

This was the TT decoder from another member wasn't it? Had he ever had it wired/powered before?

If not, perhaps an assembly/manufacturing fault. Otherwise if it worked for him prior that indicates the problem is not the decoder.
modelling era IIIa (1951-1955) Germany
Offline Dave Banks  
#12 Posted : 20 August 2020 23:26:13(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.
Alan I fear you may be right. It was my last resort to get the 4 welded center pins out. I followed what you said & all the rest came out very easily. Well when the cradle comes & I fit it, that will be the test of success or failure. Dry joints / arching is the only thing that comes to mind why this happened in the first place & as the electronics said to me this must have been going on for some time without you knowing it to produce such heat to melt the holder & not even damage the chip is weird. If all else fails I will either try to source another one or a Marklin #7686 or at worst go back to the old blue controller. Biggest drama is sourcing anything from Germany as its not coming or going out of Australia postal wise. Cursing
D.A.Banks
Offline Dave Banks  
#13 Posted : 20 August 2020 23:55:48(UTC)
Dave Banks

Australia   
Joined: 08/03/2006(UTC)
Posts: 1,026
Location: Gold Coast, Australia.
Hello Eric, all started with Ecos detecting a short somewhere & going to red. Bumping the table worked twice & I could go on for the whole day no problem. On this occasion I powered up & it all came to life. I was just refitting my ICE 3750 on the track after gluing the magnets back as described on another thread & when I hit that go button it tripped. So I pulled the track & program cables out of the Ecos & hit the button & all came to life. I went through every point & all worked. I also brought out the ohm meter & it showed a closed circuit between center studs & outer track. I re-plugged the program track in & fine. Put the main track cable back instant shutdown. I did a visual inspection of the tracks & also of the underside of the layout for anything obvious. Nothing. So I started to remove rolling stock one by one testing after each removal. I got to where I took off the Lilliput Flirt & the green light came on. So replaced the flirt on the track & hit the go button. It went to Green but the flirt emitted a motor sound effect that I did not initiate. I hit the red button but the sound continued. I pulled the track wires out of the Esu & it continued. The #6003 was lit so I pulled the wires out of that & it stopped. Note my auxiliary items is all powered via my booster like points. By this time 10 seconds had elapsed & I could smell burnt electronics. Took a bit to find. The rest you know. Once the offending decoder had been removed I tested all including the turntable manually via the blue box controller & all was well & Lilliput flirt runs fine with no ill effects. Eric yes the Bridge was lined up with direct Ecos track power being the normal entry & exit for the turntable. So that it in a nutshell & not really any wiser as to what the cause was other that arching dry joints on the PCB. I am all ears on possible theories & if someone has a used decoder for sale.

[img]UserPostedImage[/img]

The terminals 4,5,12 & 13 is the area of damage on the Holder & PCB leg holes.

Edited by user 21 August 2020 12:12:33(UTC)  | Reason: Not specified

D.A.Banks
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