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Offline Janne75  
#1 Posted : 23 July 2014 13:46:37(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Hi all,

I had some problems with an C-track turnout and it's jamming turnout motor. So before I noticed the problem was a jamming turnout motor I had partly damaged two 74460 digital decoders... Cursing

Anyway it has been fixed long time ago RollEyes .

Both 74460 turnout decoders work only in one "direction" giving pulse to turnout motors to operate in one direction. Other direction does not work as the component(s) needed for that burned with some smoke...

I would like to ask what else could be controlled with 74460 decoders working only in one direction? Maybe a device/something having some way to go back to off position after a while or something else. Can for example building interior lights be controlled digitally by these? I'm a total newbie in all electronics, so some good advices would be great ThumpUp .

Regards,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
Offline Chook  
#2 Posted : 23 July 2014 14:31:27(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Janne, I can't see the actual printing on the components after searching the "net" but I see that there are 2 resistors feeding an 8 legged integrated circuit on a 74460 decoder board. (I personally don't have a 74460 decoder or C track)
I suspect that the component that went bang was this 8 legged IC?
If the details of that IC could be photographed it may be possible to purchase a new one then replace it unless of course it is a Marklin "in house" IC.
Of course you will require some fine soldering skills and equipment to do this. (or know someone who can)
It would also be wise to check that there is a signal coming from the resistor and that the damage has not fed back to the main processing IC.

REgards.....Chook.
Offline Janne75  
#3 Posted : 23 July 2014 14:45:38(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Hi Chook,

I will try to take good enough photos of these damaged 74460's and their IC's. Then I post the photos and/or printings of the IC's in this topic.

But actually I have now working digital decoders in all of my 25 turnouts and these two could be also used to control something else instead. But better to have two functions than one so it could be worth to fix it. This must be done by someone else as I would make only more damage with my soldering iron.

Thanks in advance!

Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
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Offline Janne75  
#4 Posted : 23 July 2014 15:11:33(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Hi Chook, all,

I took these two photos of my partly damaged 74460 decoders. There is no 8 legged components, but you can now see the components and the texts on them. Some of the components have different texts and some components have identic texts:

UserPostedImage

UserPostedImage

I tried to look the components and can´t see any external damages in them Confused .

Regards,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
Offline Renato  
#5 Posted : 23 July 2014 15:56:32(UTC)
Renato

Italy   
Joined: 19/03/2004(UTC)
Posts: 976
Location: Gorizia, Italy
Hi Janne,

It is impossible to say anything, without having the PCBs in your hands and perform some tests, measurements, etc.

I could only think that the power output stage controlling the faulty turnout solenoid has blown, even if it is not burnt as per a short circuit.

Maybe it was only an overheating for a very long time.

What was the defect of the turnout solenoid: solenoid in short circui or what else?

My suggestion: you could use the working output to control one uncoupling track.

Cheers

Renato
Offline Janne75  
#6 Posted : 23 July 2014 16:14:47(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Hi all,

Harri from Finland (Ukko-Pekka) sent me an SMS and he found out what is damaged in these. Look at the components with markings 1F7 near the green cables. These have both some spots = damage in them.

Thanks to all and especially to Harri ThumpUp . You have VERY good eyes.

I don´t have any uncoupler tracks, but maybe in the future. I use normally my Telex locos to do the uncoupling or that black plastic uncoupling tool.

Edit: I did some Google search and it looks to be a "Fast Recovery Rectifiers Diode 1F7". Please correct me if I´m wrong?

Regards,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
Offline H0  
#7 Posted : 23 July 2014 17:21:49(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 15,251
Location: DE-NW
Originally Posted by: Janne75 Go to Quoted Post
Edit: I did some Google search and it looks to be a "Fast Recovery Rectifiers Diode 1F7". Please correct me if I´m wrong?
Looks like a transistor.

Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
UserPostedImage
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Offline Renato  
#8 Posted : 23 July 2014 17:37:19(UTC)
Renato

Italy   
Joined: 19/03/2004(UTC)
Posts: 976
Location: Gorizia, Italy
Hi Janne,

It has 3 terminals and therefore it is a power transistor.

I was having a look on the web and found that:

LINK

even if it is not 100% applicable.

Cheers

Renato
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Offline Janne75  
#9 Posted : 23 July 2014 17:41:24(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Originally Posted by: H0 Go to Quoted Post
Originally Posted by: Janne75 Go to Quoted Post
Edit: I did some Google search and it looks to be a "Fast Recovery Rectifiers Diode 1F7". Please correct me if I´m wrong?
Looks like a transistor.



Ok, thanks. So it looks like that 1F7 can mean many different electronic components. Anyway, if these transistors can be changed these turnout decoders can maybe be fixed then. But as these have very, very tiny solderings it is impossible for me, my skills and equipment to replace them. I think those components are very cheap.

Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
Offline kiwiAlan  
#10 Posted : 23 July 2014 21:26:25(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,067
Location: ENGLAND, Didcot
Originally Posted by: Janne75 Go to Quoted Post
Originally Posted by: H0 Go to Quoted Post
Originally Posted by: Janne75 Go to Quoted Post
Edit: I did some Google search and it looks to be a "Fast Recovery Rectifiers Diode 1F7". Please correct me if I´m wrong?
Looks like a transistor.



Ok, thanks. So it looks like that 1F7 can mean many different electronic components. Anyway, if these transistors can be changed these turnout decoders can maybe be fixed then. But as these have very, very tiny solderings it is impossible for me, my skills and equipment to replace them. I think those components are very cheap.



That is a problem with SMD components. My pick would be one of the BC847 transistors listed in that link.

If you were in the UK I would say send them to me, and I could deal with them, but the costs from where you are would make it as cheap to get a new decoder Mad but then the new decoders are DCC as well and don't require setting up switches.
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Offline Janne75  
#11 Posted : 24 July 2014 00:23:15(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Originally Posted by: kiwiAlan Go to Quoted Post
That is a problem with SMD components. My pick would be one of the BC847 transistors listed in that link.

If you were in the UK I would say send them to me, and I could deal with them, but the costs from where you are would make it as cheap to get a new decoder Mad but then the new decoders are DCC as well and don't require setting up switches.


Hi Alan,

Thanks. I can send these to you in a letter with very cheap cost if you want to fix them? Please send me PM if you are interested. I like these older 74460 decoders as I want to have those easy to set up DIP switches. I also like older digital locomotives with DIP switches and adjustable pots so I must be a very weird person LOL .

Regards,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
Offline Renato  
#12 Posted : 24 July 2014 00:50:41(UTC)
Renato

Italy   
Joined: 19/03/2004(UTC)
Posts: 976
Location: Gorizia, Italy
Originally Posted by: kiwiAlan Go to Quoted Post
That is a problem with SMD components. My pick would be one of the BC847 transistors listed in that link.

Hi,

With only 100 mA collector current, I think this is not the right choice, as the solenoid current is greater than 100 mA.

Cheers

Renato


Offline Chook  
#13 Posted : 24 July 2014 03:55:39(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Hi Folks - yep that is a different printed circuit board to the one I saw on the "net". It did however have the same DIP switch address switch on it.

And yes the component with the 1F7 marking (the one with the smoke escape hole BigGrin ) will be a darlington transistor pair (to get the appropriate amplification) to actuate the coil and it will also have a protection diode in built to protect itself from the back EMF generated by the coil.
I am pressed for time at the moment but will investigate further for a replacement.

Regards.....Chook.
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Offline kiwiAlan  
#14 Posted : 24 July 2014 10:53:14(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,067
Location: ENGLAND, Didcot
Originally Posted by: Chook Go to Quoted Post
Hi Folks - yep that is a different printed circuit board to the one I saw on the "net". It did however have the same DIP switch address switch on it.

And yes the component with the 1F7 marking (the one with the smoke escape hole BigGrin ) will be a darlington transistor pair (to get the appropriate amplification) to actuate the coil and it will also have a protection diode in built to protect itself from the back EMF generated by the coil.
I am pressed for time at the moment but will investigate further for a replacement.

Regards.....Chook.


OK the Zetex ZXTP05120HFF darlington has a marking of 1F7 (the complementary one to it is listed on the link above as 1F6, which is what put me on the trail of it).

Datasheet at http://diodes.com/datasheets/ZXTP05120HFF.pdf

And IIRC a PNP is what has historically been used by Marklin as output drivers in s88 decoders and the like, and as the 74460 is a cut down s88 they would likely follow the same circuit.

Now to source some devices.

[edit]
RS have them, catalogue number 712-2882 @ GBP0.40 ea in 10 off.
[/edit]
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Offline walter__  
#15 Posted : 24 July 2014 10:54:23(UTC)
walter__

Belgium   
Joined: 30/12/2013(UTC)
Posts: 19
Location: Antwerp
Hi all,

Closest by is a Zetex NPN darlington marked 1F6 looking at thePCB I would a MMBTA13 a Fairchild Semiconductor 1A darlington.
Has no protection diode but one shows on the PCB. Costs some 0.15 €

Hope this helps BigGrin

Walter


Ooops.. if a PNP is required, a DIODES INC. - FMMT734 - DARLINGTON TRANSISTOR, SOT-23 could do, 800mA (5A Peak Pulse Current) 0.31€ per 5
see http://be.farnell.com/di...sistor-sot-23/dp/9525106
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Offline Chook  
#16 Posted : 24 July 2014 14:05:20(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Alan you have "thrown a spanner into the works". The PNP info is interesting.
Ok so far I can tell you that the IC on the far left (4011) is a CMOS quad 2 input NAND gate unit which usually runs at 12 volts DC. (range up to 20 volts)
If I assume (i know that is dangerous as the 4011 will also run as low as 5v) that the whole board is running at 12 volts, and we know that the base resistor of the IF7 is a 4.7k then ohms law gives me a base current of 2.55 mA. So far so good.

It also appears that the collector of IF7 is connected to either the blue or green wires (depending on the solenoid direction) with a common yellow wire as the return.
Now here is where it gets peculiar - that yellow common appears to return through a 2.7k resistor whose maximum current at 12v is 4.4mA which I believe is no where near enough to operate that solenoid coil.

Also of interest is those 2 large cylinders with the brown/purple (?) stripes appear to sit across the collectors of our 2 transistors - these may in fact be the diode protection I mentioned earlier. (however diodes are usually packaged in glass cylinders as elsewhere on the PCB)

So at this stage we need someone with a multimeter who has access to this same model of printed circuit board to do some measurements for us.



Regards.....Chook.
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Offline Renato  
#17 Posted : 24 July 2014 17:18:52(UTC)
Renato

Italy   
Joined: 19/03/2004(UTC)
Posts: 976
Location: Gorizia, Italy
Hi all,

I had a look at my 74460: it has as output stage for both solenoids a ZETEX ZDS1002 (so the situation is a little bit different but the functions must be the same).

Here is a PDF of the related schematics found on Stummiforum:

LINK

For the electronics people;

terminal A1 is connected to YELLOW
terminal C1 is connected to BLUE
terminal C2 is connected to GREEN
terminal E1 is connected to + of the board
terminal E2 is connected to + of the board
terminal B2 is connected to a resistor

I am not able to see the connection of terminal A2 to YELLOW and the connection of terminal B1...
Maybe the connections are hidden under the ZDS1002.

So definitely the 2 components mentioned by Chook are diodes.

Hope this could help to replace the original SMD components with equivalent transistors/components.

Cheers

Renato
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Offline Janne75  
#18 Posted : 25 July 2014 01:14:14(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Hi all,

Thank you to all from searching info and help. As I'm not an electronics expert these details goes beyond my understanding. I have studied some basics of electronics in two schools around 15-20 years ago so I can just remember the Ohms law and some similar very basic things BigGrin .

It is interesting to see how highly experienced people we have on this forum ThumpUp . Maybe others will find these informations useful later when their 74460 decoders may blow out. I hope they will not get them damaged, but I'm 100% sure I'm not the only one who have had bad luck with jamming turnout motors and got as a result damaged 74460's.

Regards,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
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Offline Chook  
#19 Posted : 25 July 2014 14:04:12(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Renato thanks for your reply - your PCB type was the one I looked at originally with the 8 pin IC.

so at this stage we need someone with a meter who can get some measurements for us. ANYONE??

Janne I have just looked up Australia Post's website and the thieving sods want $20 for a return 500g parcel to Finland. I suspect that this would be most uneconomical for you?
The concern I have is that the blown transistor has also damaged the output port on the main IC - the one which does the decoding and timing which will be impossible to replace. So even if we get the blown transistor replaced there is still a possibility that the other channel is still faulty.

The local replacement of a single transistor would be relatively cheap and easy if you can find someone with the skills and tools to do it.
I hate to see good electronics discarded for the want of a simple repair. (I despair at some of the stories of blown decoders on this forum which inevitably end up in the bin because owners don't have the support to get them further investigated)

Regards......Chook
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Offline Janne75  
#20 Posted : 26 July 2014 02:21:42(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Thanks Chook,

I can try to find someone here in Finland to do the replacement of the transistors. Maybe Harri (Ukko-Pekka) here from Finland can help me as he has better electronics soldering skills as he has studied this?

Cheers,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
Offline Chook  
#21 Posted : 26 July 2014 04:07:01(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Janne if Harri has any questions regarding this I am happy to help him along.

I suspect that if Harri is successful with yours that he may be very busy in the future!

Regards.........Chook.
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Offline Janne75  
#22 Posted : 26 July 2014 09:58:47(UTC)
Janne75

Finland   
Joined: 23/03/2012(UTC)
Posts: 2,550
Location: Finland
Originally Posted by: Chook Go to Quoted Post
Janne if Harri has any questions regarding this I am happy to help him along.

I suspect that if Harri is successful with yours that he may be very busy in the future!

Regards.........Chook.


Thank you in advance ThumpUp Smile .

But please remember these 74460 decoders don't fail very often. These two I damaged would still be ok if I had tested that turnout with manual lever and noticed it was jamming. It was not the decoders fault that I was so stupid I tried to operate a jamming turnout motor. So the decoders took too much current then and these damages are the result.

But if someone succesfully could fix those very unreliable Märklin turnout motors 74490 and 74491 with a cheap fix he or she could earn good moneys. Those two Märklin product numbers have some kind of curse in them.

Cheers,
Janne
Märklin H0 digital layout. I have analog and digital H0 Collection. Rolling stock mostly from era I, II, III and IV. Märklin 1 gauge beginner.
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