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Offline PMPeter  
#1 Posted : 29 June 2016 00:41:47(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,273
Location: Port Moody, BC
Every once in awhile you make an eBay purchase and it ends up being a damaged item. I have bought numerous K83 decoders over the last 3 years and up until today all have worked perfectly. Today I installed one of the newer plug style K83s that I obtained sometime in the last 6 months and the minute I turned the power on, the CS2 went into an overload shutdown. Disconnecting the power from the K83 got rid of the overload.

No magical smoke, no burnt smell, just a dead short. So I opened it up and found a burnt component as can be seen in the attached photos.

Circuit board

K83

Burnt component lower right

Burnt component


Since I know we have a number of electronics experts on this forum, does anyone know what this component is? It has 2 bands on it, but due to the burning I cannot tell what colour they were. It is not a capacitor nor resistor since they are all identified on the circuit board.

Since I do not know who the seller was for this unit, and due to the timeframe involved I no longer can go after the seller and can only try and repair it or throw it out.

Cheers
Peter
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Offline H0  
#2 Posted : 29 June 2016 08:04:55(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 15,254
Location: DE-NW
Hi, Peter!

With high certainty it is a diode, connecting "red" with the centre socket of each turnout output.

I cannot estimate the rating of the diode: 1 A, 2 A, 5 A.

I think I'd try 1 A or 2 A if it was mine - better to burn the diode and not the output transistors in case of trouble.

Maybe someone can identify the rating of the original diode.

BTW: When you open the connection between "DATEN" and "+UB" then you should be able to operate the turnouts with external power (AC or DC) instead of track power.
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
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Offline Goofy  
#3 Posted : 29 June 2016 10:44:07(UTC)
Goofy


Joined: 12/08/2006(UTC)
Posts: 8,993
It´s 2 amp.
Märklins k83 do accept tolerance maximum output at 2 amps load.
H0
DCC = Digital Command Control
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Offline PMPeter  
#4 Posted : 29 June 2016 16:02:23(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,273
Location: Port Moody, BC
Thanks to both of you.

Does it matter what type of 2A diode I get as long as the voltage rating is greater than 25V and it is roughly the same physical size?

I'm still not sure what the second band on the burned out one indicates since most of the ones I can find online have a single band.

Peter
Offline Minok  
#5 Posted : 30 June 2016 01:01:54(UTC)
Minok

United States   
Joined: 15/10/2006(UTC)
Posts: 2,310
Location: Washington, Pacific Northwest
Originally Posted by: PMPeter Go to Quoted Post
Thanks to both of you.

Does it matter what type of 2A diode I get as long as the voltage rating is greater than 25V and it is roughly the same physical size?

I'm still not sure what the second band on the burned out one indicates since most of the ones I can find online have a single band.

Peter


You do have to get the right kind of diode, as there are several types of diodes in the world of electronics designed for differing applications. (I cannot at present see the images as my employer blocks access to dropbox).

There's always a line/ring at one end (black or light colored) that is the CATHODE side of the diode - that needs to be installed the right way around + the right rating and type needs to be used.

UserPostedImage

Some diodes are placed to bleed off high spike voltages (at relays and switches) and others to ensure the direction of flow of current (eg in rectifiers), etc. and the type and rating of the diode matters for the correct function of the electronic circuit.
Toys of tin and wood rule!
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Offline clapcott  
#6 Posted : 30 June 2016 02:17:29(UTC)
clapcott

New Zealand   
Joined: 12/12/2005(UTC)
Posts: 2,433
Location: Wellington, New_Zealand
Originally Posted by: H0 Go to Quoted Post

I think I'd try 1 A or 2 A if it was mine

Original units used a 1N4001 (1 Amp rated)
other references I have are to a 1N4935 (also 1Amp rated)

Quote:

- better to burn the diode and not the output transistors in case of trouble.

Concur , especially with the SMD transistors on this board.

You may wish to do a continuity test (From Brown, to each of the blues (Gr/Rd) )
if you have a direct short , one of driver transistors has failed and may be the root cause. (i.e. the diode would have got hot but may not actually have failed before the controller cutout.

In my experience (which are only a couple - these are good/tolerant devices) , if there was only one fault (Yellow IN as Tom mentions) , the diode should be able to be replaced to get you operating again.
Peter
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Offline PMPeter  
#7 Posted : 30 June 2016 04:38:13(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,273
Location: Port Moody, BC
Originally Posted by: clapcott Go to Quoted Post

You may wish to do a continuity test (From Brown, to each of the blues (Gr/Rd) )
if you have a direct short , one of driver transistors has failed and may be the root cause. (i.e. the diode would have got hot but may not actually have failed before the controller cutout.

In my experience (which are only a couple - these are good/tolerant devices) , if there was only one fault (Yellow IN as Tom mentions) , the diode should be able to be replaced to get you operating again.


Continuity check between the brown and each of the 8 blue lead sockets are all open circuit, so it looks like it is just the diode.

I checked out both of the diode numbers that you provided and they all appear to be single banded units. Any idea why the Marklin installed component has 2 bands? Is it perhaps a special component?

So if I understand both you and Tom correctly, if I scrape off the connection between DATEM and +UB I can feed the K83 red digital power connection at the top of the K83 and from another source to the red plug at the bottom of the K83, similar to the Viessmann 5211.

Thanks
Peter
Offline PMPeter  
#8 Posted : 30 June 2016 04:42:18(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,273
Location: Port Moody, BC
Originally Posted by: Minok Go to Quoted Post

You do have to get the right kind of diode, as there are several types of diodes in the world of electronics designed for differing applications. (I cannot at present see the images as my employer blocks access to dropbox).


Thanks. Perhaps when you are home you can look at my photo and see if you have an idea why the failed unit has 2 bands.

Offline Shamu  
#9 Posted : 30 June 2016 04:51:59(UTC)
Shamu

Australia   
Joined: 12/07/2011(UTC)
Posts: 1,068
Location: In a building site in Yeppoon
The diode in question is a 1n4935. From memory the dual bands most likely indicate Russian (or Soviet) manufacture.

EDIT:
Whoops, sorry Peter just realised you had mentioned that Blushing .
Sad when its cheaper to buy a new 29640 starter set from Germany than a CS2 on its own in Oz, welcome to the joys of Marklin down under .
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