Heidi loco rebuild

Airbuspilot

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25 May 2021
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Hi

I had two locos in pieces, one I have now fixed with a great deal of help from this forum the second is my next maintenance project.

It is an LGB Heidi steam loco, originally taken apart (not by me) to add a run on capacitor. If someone can please identify the boards for me and suggest a suitable capacitor I would appreciate it. The only identification I can see is on the large board DMG2301L. Seems sensible to finish the project rather than reassemble only to take it all apart again in a couple of months.

How to fix the capacitor will be my next question :(

Robin

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phils2um

Phil S
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HI Robin,

This info will probably not help but could point you and others in the right direction.

The lower board is a decoder interface board. It has MLGB's mtc27 interface. The upper board is the decoder which connects with 27 pins (14 on one end and 13 on the other) that plug into two single row sockets on the interface board.

The latest MLGB multi-protocol replacement sound decoder, No. 55029, has this same mtc27 interface. The literature for the 55029 decoder indicates that additional voltage buffer capacity can be added with the No. 55429 Voltage Buffer. The 55429 Buffer and the 55029 decoder's onboard buffer are both extensively controlled by CV settings in the decoder. It is not clear from the LGB literature just how this buffer connects to the decoder. The LGB literature does also reference a Märklin Voltage Buffer, No. 60974 as also being compatible. The 60974 Voltage Buffer manual shows this buffer is connected via the SUSI bus. This also explains how the decoder can control functioning (via SUSI) of the 55429 buffer. There is a minimum decoder firmware update version required for the buffer to properly function, v.3.2.0.1 or higher. Whether this update can be applied to older mtc27 decoders such as in your Heidi or my No. 24450, Ge 2/4 is a question I intend to put to the Märklin digital support guys.

Page 35 34 of the 55029 decoder manual, https://static.maerklin.de/damcontent/53/ef/53efc34f6cf3a488158eebcb145768d31597737980.pdf, has at least a partial list of LGB locos with the mtc27 interface.

Edited to correct page no.
 
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Airbuspilot

Registered
25 May 2021
92
3
72
Cyprus
Country flag
HI Robin,

This info will probably not help but could point you and others in the right direction.

The lower board is a decoder interface board. It has MLGB's mtc27 interface. The upper board is the decoder which connects with 27 pins (14 on one end and 13 on the other) that plug into two single row sockets on the interface board.

The latest MLGB multi-protocol replacement sound decoder, No. 55029, has this same mtc27 interface. The literature for the 55029 decoder indicates that additional voltage buffer capacity can be added with the No. 55429 Voltage Buffer. The 55429 Buffer and the 55029 decoder's onboard buffer are both extensively controlled by CV settings in the decoder. It is not clear from the LGB literature just how this buffer connects to the decoder. The LGB literature does also reference a Märklin Voltage Buffer, No. 60974 as also being compatible. The 60974 Voltage Buffer manual shows this buffer is connected via the SUSI bus. This also explains how the decoder can control functioning (via SUSI) of the 55429 buffer. There is a minimum decoder firmware update version required for the buffer to properly function, v.3.2.0.1 or higher. Whether this update can be applied to older mtc27 decoders such as in your Heidi or my No. 24450, Ge 2/4 is a question I intend to put to the Märklin digital support guys.

Page 35 of the 55029 decoder manual, https://static.maerklin.de/damcontent/53/ef/53efc34f6cf3a488158eebcb145768d31597737980.pdf, has at least a partial list of LGB locos with the mtc27 interface.
Many thanks Phil

I think this is going to be too complicated for me at the moment, probably revert to plan B and put it back together for a future try when I understand a bit more. We do have several stay alive units but i don't know which ones, I will have a look next opportunity but for another day.

Robin