LGB 20882 Mallet - Analogue to DCC

PhilP

PhilP

G Scale, 7/8th's, Electronics
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All,
Have been given a 20882 Unitah Mallet with analogue sound, and been asked to put a decoder in it..
Having (finally) got the beastie apart, I find a (very) large analogue sound board, and a smaller regulator board with the motor blocks connected. - To say space is at a premium is an understatement!
I have been asked 'to chip it'. - Single decoder, XL I have ready.

There is a 4-way DIP switch block on the larger circuit board, but no obvious point(s) to pickup for a decoder..

This loco is almost in mint condition.. I am very tempted to tell the owner to leave it alone.

Any thoughts / pointers on whether it would be better to leave this 'as is'..
OR, any pointers as to fitting the decoder. - Looks like a major rewire job.

Many Thanks,
PhilP
 
One idea is to fit a sound decoder leaving only the speaker and firebox lights of the original sound system.
Plenty of space left that way.
You may well recover some of the difference in cost between a normal and sound decoder by selling the original sound board. These boards are currently on offer from Germany for 89.90 Euro, the seller used to let them go on ebay for around 35 Euro but they are no longer available via ebay.
 
The loco's instructions are rather vague about how to connect a decoder, which suggests that there is no real provision for one. My inclination would be to remove the connector blocks (carefully!) from both sets of motor/ track connections and use the bared wires to connect to your XL.

According to the instructions there is a socket for an LGB 55026 interface cable somewhere, so that should handle the functions, including sound. If the instructions are accurate, there should be two banks of dip switches, one on each board. Those on the main board are all changed to "off". On the sound board, just dip switch 1 is changed to "off". From the instructions the sound board is serial only, so the DCC controller will need to be set to 14 speed steps and serial.

The only other way to do this would be - as you suggest - getting an XLS with the appropriate sounds and then gutting the loco's wiring. That might be preferable as you'd be able to set up the loco to run in parallel mode for functions with 28 speed steps. You also get more space in the loco!

Good luck!

See here for instructions:
http://www.champex-linden.de/lgb_pr...63C66E4EE743185256930007176AF/$FILE/20882.pdf < Link To http://www.champex-linden...7176AF/$FILE/20882.pdf
 
I think you'll find the original board similar to this.


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It's intended for two LGB decoders but hasn't got facilities to mount either on the board.
There are eight pins near the dip switches, four each for the main (motor and pickup) wires from each motor block and one six pin socket, also next to these eight pins and dip switches, to take a function interface cable from one of the decoders.
I presume a single higher power decoder would be the way to go now these are available, commoning the relevant pins from each motor block. Messing up the latter could blow a decoder so I suggest you get your decoder supplier to give you precise instructions unless the decoder is supplied with two sets of colour coded main wires
 
Thanks all.. Been out for the day.

Neil, board similar, but not the same.. Motor connections at each end. Gold circle sticker, and date on motor blocks suggests 1994 vintage. board is 20882-153 and sound board is 151.
4-way DIP switch on sound board, NO DIP switch on regulator board.
I think this is an early version. It has not been run very much at all, and the moulding and finish seems very 'crisp' compared with some of the offerings I have seen.
I intend to ring the owner, and check he wants it 'fiddling' with.
I can certainly do the job. just I feel I may be devaluing a nice loco by 'messing'..

I will eat, and make the call, but would welcome the Groups thoughts..
PhilP
 
PhilP said:
Thanks all.. Been out for the day.

Neil, board similar, but not the same.. Motor connections at each end. Gold circle sticker, and date on motor blocks suggests 1994 vintage. board is 20882-153 and sound board is 151.
Click to expand...

If it is 1994 vintage, it pre-dates MTS by 4 years, so not surprised it doesn't have the pins/sockets expected. I assume it has "D" type gearboxes with four pole leads, not just 3?
I think a complete rewire and an XLS chip is the way to go if your client really wants the job done. A long and slightly tedious job, but not especially difficult.
 
Having chipped quite a few Lcomotives of varying vintage I concur with Whatlep.

Just strip out all the old board and rewire direct from Motor and Pickup. If it is one of those nasty 3 wire jobs from the chassis you will heed to dismantle them to separate pickups from the motor. Not difficult but you have to do it twice! Once you have two wires from motor and two to track pickup for each bogie it is easy. Then I would also suggest upgrading the light bulbs too the higher voltage ones for ease of replacement in the future.

Good luck,
JonD
 
PhilP said:
I intend to ring the owner, and check he wants it 'fiddling' with.
I can certainly do the job. just I feel I may be devaluing a nice loco by 'messing'..
I will eat, and make the call, but would welcome the Groups thoughts..
PhilP
Click to expand...
If the owner wishes to run it then I would say chip it.
If he wishes it to remain a mint museum piece or shelf queen don't bother.
 
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