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Offline 3rail4life  
#1 Posted : 13 February 2016 09:55:18(UTC)
3rail4life

United States   
Joined: 23/12/2011(UTC)
Posts: 425
Location: Northern California
Hello All,

Recently one of my customers gave me the opportunity to repair some 6021's that were shorting out when power was supplied. I believe they may have been damaged by an improper transformer connection to the output terminals, or just failed from old age, not exactly sure, but felt it would be worth a try to fix them. Thankfully I was able to get some guidance on how to get started from here: Reparaturen. It is short and in German, so I thought for the forum I could explain and expand on it in English for those that may be interested in reviving their 6021's.

The first step is to remove the external case screws from the heat sink and the plugs that hold the case together, the two screws are easy, the four plugs, a bit more complicated:


Drilling a small hole in the center of the plug allows a screw to be attached.

Once attached, a gentle pull on the screw with a set of pliers is all that is needed to remove it.

With the controller face down, the base may lifted off. The lower circuit board can then be litfed out and flipped over into the base to access the remaining heat sink screws and transistors.

Here the challenge is getting the transistor screws removed, the circuit board in front of them prevents easy access with a screwdriver, I used pliers to loosen them. Once they are removed there is one more screw holding the heatsink to the board that needs to be removed and heat sink is off.

Now the transistors may be desoldered, take note of the values and their position for the installation back on to the heat sink. the desoldering is probably the most difficult part, take care not to damage the board or any of the other surface components when removing the transistors and solder, the thru-holes must have all excess solder removed before reassembly.

Install the new transistors in the correct orientation on the heat sink.

Solder new transistors to the board and replace bottom heat sink screw.

Reassemble Control Unit and test...


All three 6021 units I received for repair had a least one bad transistor, I replaced all three in each with new ones and each worked well upon completion.

Parts used on each: 1 x BDW93CFP, 2 x BDW94CFP, STMicroelectronics brand. Other brands and types are compatible, just be sure they are of the correct values and insulated from the heat sink.

Tools used: 1.8 mm drill and pin vise, 2 mm self tapping screw, small serrated jaw pliers, phillips head screwdriver, solder station, solder wick, solder and flux.

Good desoldering and soldering skills plus knowledge of integrated circuits are required for this repair, please do not attempt if not proficient.

Cheers,
Gordon

Edited by moderator 11 July 2016 13:41:41(UTC)  | Reason: Topic made 'Sticky'

thanks 22 users liked this useful post by 3rail4life
Offline mike c  
#2 Posted : 13 February 2016 10:24:22(UTC)
mike c

Canada   
Joined: 28/11/2007(UTC)
Posts: 7,110
Location: Montreal, QC
In my case, the buttons do not react when pushed. I figure there is a plastic form underneath the buttons which holds the buttons in place and presses down on the circuit board at the appropriate place. There may be some dust or other contaminant interfering with pressing a button or it may just be that the plastic form is not sitting properly in place.
Did you have any luck accessing that part of the unit and what would I need to do to repair it?
When I have seen similar issues on TV and VCR remotes, they were usually done for.

Regards

Mike C
Offline 3rail4life  
#3 Posted : 13 February 2016 18:21:48(UTC)
3rail4life

United States   
Joined: 23/12/2011(UTC)
Posts: 425
Location: Northern California
The controls are on a second board which attaches to the top of the case, it is accessible when the case is open but I did not wish to disturb any of the buttons, I left that part of the unit in place and can not advise on the disassembly.

Interestingly, the article I referenced for the case disassembly, Reparaturen , also shows how to repair a TV remotes keys, not sure if the trick works with the 6021 though.

Cheers,
Gordon
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Offline Purellum  
#4 Posted : 13 February 2016 18:58:38(UTC)
Purellum

Denmark   
Joined: 08/11/2005(UTC)
Posts: 3,310
Location: Mullerup, 4200 Slagelse
Cool

The contacts in a 6021 look like these:

contacts

You can buy new ones and exchange them; but I don't think you can fix a broken one.

Be sure to have everything ESP-protected when you solder on the 6021.

The contacts in a mobile station is the same type as shown on the "Reperaturen" page on the TV-remote.

Per.

Cool
If you can dream it, you can do it!

I, the copyright holder of this work, hereby release it into the public domain. This applies worldwide.

In case this is not legally possible:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

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Offline clapcott  
#5 Posted : 13 February 2016 21:02:06(UTC)
clapcott

New Zealand   
Joined: 12/12/2005(UTC)
Posts: 2,406
Location: Wellington, New_Zealand
Originally Posted by: 3rail4life Go to Quoted Post
.... repair some 6021's that were shorting out when power was supplied.
I believe they may have been damaged by an improper transformer connection to the output terminals, ....


I concur. My experience is that 95% (yes I have done more than 20) of these failures are with the driver transistors and that most can be attributed to a Yellow-to-red mix up. Although a couple were from a lightening strike to the house.

I also agree with replacing the transistors in matched pairs. Even if you have an exact vendor/ID replacement for the obviously failed one, his mate is most likely stressed.

I do think that the design is good. If something has to fail, you want it to 1) cause an obvious fault 2) produce an obvious symptom 3) fail in such a way (sacrificial) that additional impact to internal components is (largely) prevented. And these transistors are really the easiest of the components to replace.

P.S. I would say there are 3 failure symptoms, depending exactly on how the transistors fail.
1) One transistor fails with a short - this causes the 6021 to appear to work with numbers displayed and keypad working, but the red "track power light" will turn off as soon as you try to turn it on
2) Both transistors short - causing the transformer that supplies the 6021 to cutout
3) a transformer fails but open (does not short) - simply no power gets to the track
Peter
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Offline Mark5  
#6 Posted : 15 February 2016 07:36:07(UTC)
Mark5

Canada   
Joined: 29/01/2012(UTC)
Posts: 1,204
Location: Montreal
Mike,

You can easily pick these up from Abra or Addison here in Montreal.
If you need any help with it, let me know.
- Mark

Originally Posted by: Purellum Go to Quoted Post
Cool

The contacts in a 6021 look like these:

contacts

You can buy new ones and exchange them; but I don't think you can fix a broken one.

Be sure to have everything ESP-protected when you solder on the 6021.

The contacts in a mobile station is the same type as shown on the "Reperaturen" page on the TV-remote.

Per.

Cool


Interested in history of DB, DR and FS circa 1955 to 1965. Fan of signals, catenary, stations and yards.
Father of four girls running an exhibition layout, the Mädchenbahn--
https://www.marklin-user...rce.ashx?i=30519&b=1
Large version of my present avatar-- https://www.marklin-user...rce.ashx?i=29910&b=1
Source of previous avatar in "zoomify" detail-- http://bit.ly/1QqMgL0
Offline river6109  
#7 Posted : 14 August 2016 10:44:14(UTC)
river6109

Australia   
Joined: 22/01/2009(UTC)
Posts: 13,523
Location: On 1965 Märklin Boulevard just around from Roco Square
Well thanks to Peter and his worthwhile assistance and all the right instruction I've received, my 6021 works fine, as mentioned before, bought it second hand and only tried it out recently for a friends locos and to my embarrassment the loco numbers didn't react to the loco. did the same as above.

part of being able to repair them I wouldn't like to have a guess how much they charge for repairs if you send it into Märklin + the postage cost from and to Australia.

John
https://www.youtube.com/river6109
https://www.youtube.com/6109river
5 years in Destruction mode
50 years in Repairing mode
Offline Ton Schluter  
#8 Posted : 08 March 2021 18:41:04(UTC)
Ton Schluter

Netherlands   
Joined: 08/03/2021(UTC)
Posts: 1
Location: Gelderland-Zevenaar
I do have experience in repair 6021 's but found out that there are different versions of the printed circuit bords. Another source told me that an other weak point is the diode bridge but sofar I do not have experimented that. It would be very helpful to have a schematic diagram. And I did not find any one in all the yeard that I use the 6021 ones. They are still asked because of the ease of changing loc numbers. I am happy with this post. Thanks for that. Ton

Edited by moderator 08 March 2021 23:43:49(UTC)  | Reason: Removed quote of entire first post...

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Offline tonyfh  
#9 Posted : 08 March 2021 19:31:07(UTC)
tonyfh


Joined: 17/04/2004(UTC)
Posts: 98
Location: Netherlands
Hello Ton, All,

Don't ask where I found it but it was a long time ago and I saved it, a schematic diagram of a 6021 control unit.

Schema van Marklin 6021 control unit.pdf (832kb) downloaded 52 time(s).

from 2007, really a long time ago.

Greetings, Tony.
thanks 1 user liked this useful post by tonyfh
Offline Tkid  
#10 Posted : 01 May 2021 15:26:13(UTC)
Tkid

Netherlands   
Joined: 03/02/2015(UTC)
Posts: 1
Location: Utrecht, Amersfoort
Thank you for this useful information. I just unpacked my Märklin stuff and started building after quite some years. I just found out my 6021 has an issue: the L diod, and with that the whole thing, doesn't work. If anyone has suggestions.....

Cheers, have nice weekend,
Jos

Originally Posted by: 3rail4life Go to Quoted Post
Hello All,

Recently one of my customers gave me the opportunity to repair some 6021's that were shorting out when power was supplied. I believe they may have been damaged by an improper transformer connection to the output terminals, or just failed from old age, not exactly sure, but felt it would be worth a try to fix them. Thankfully I was able to get some guidance on how to get started from here: Reparaturen. It is short and in German, so I thought for the forum I could explain and expand on it in English for those that may be interested in reviving their 6021's.

The first step is to remove the external case screws from the heat sink and the plugs that hold the case together, the two screws are easy, the four plugs, a bit more complicated:


Drilling a small hole in the center of the plug allows a screw to be attached.

Once attached, a gentle pull on the screw with a set of pliers is all that is needed to remove it.

With the controller face down, the base may lifted off. The lower circuit board can then be litfed out and flipped over into the base to access the remaining heat sink screws and transistors.

Here the challenge is getting the transistor screws removed, the circuit board in front of them prevents easy access with a screwdriver, I used pliers to loosen them. Once they are removed there is one more screw holding the heatsink to the board that needs to be removed and heat sink is off.

Now the transistors may be desoldered, take note of the values and their position for the installation back on to the heat sink. the desoldering is probably the most difficult part, take care not to damage the board or any of the other surface components when removing the transistors and solder, the thru-holes must have all excess solder removed before reassembly.

Install the new transistors in the correct orientation on the heat sink.

Solder new transistors to the board and replace bottom heat sink screw.

Reassemble Control Unit and test...


All three 6021 units I received for repair had a least one bad transistor, I replaced all three in each with new ones and each worked well upon completion.

Parts used on each: 1 x BDW93CFP, 2 x BDW94CFP, STMicroelectronics brand. Other brands and types are compatible, just be sure they are of the correct values and insulated from the heat sink.

Tools used: 1.8 mm drill and pin vise, 2 mm self tapping screw, small serrated jaw pliers, phillips head screwdriver, solder station, solder wick, solder and flux.

Good desoldering and soldering skills plus knowledge of integrated circuits are required for this repair, please do not attempt if not proficient.

Cheers,
Gordon


thanks 1 user liked this useful post by Tkid
Offline marklinist5999  
#11 Posted : 01 May 2021 16:57:58(UTC)
marklinist5999

United States   
Joined: 10/02/2021(UTC)
Posts: 459
Location: Michigan, Troy
Can a 6001 trafo be repaired? Mine is dead. It was fine beofre. No major shorts. I did leave it plugged in overnite once.
Offline Bigdaddynz  
#12 Posted : 01 May 2021 21:52:33(UTC)
Bigdaddynz

New Zealand   
Joined: 17/09/2006(UTC)
Posts: 17,769
Location: New Zealand
Possibly....

I had a grey 60va transformer fail. It was opened using the same method as described for the 6021 above. Inside the transformer are two zeneer diodes one of which had failed. After replacing both diodes the transformer worked fine and continues to do so.

I don't know if this is pertinent to your repair but it's worth trying.
thanks 1 user liked this useful post by Bigdaddynz
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