LGB Uintah mallett

T

Tim Brien

Registered
I had a quick look but could not see my posting from the previous forum. A few months ago I purchased a complete sound setup from a new LGB Sumpter Valley Mallett including the wheel sensor a nd bell/whistle trigger switch.

Naively, I assumed that it would be a direct install on my Uintah Mallett as they are basically the same units. Alas, a tale of woe. The sound unit arrived from the States and was installed. Immediately I had a short circuit. I removed the main board and sound board and refitted the stock analogue board and all was well. I informed the seller that I believed the Sumpter main board was faulty and he kindly arranged a replacement main board from Germany.

Well the new board arrived some weeks later and was installed. Alas, the loco shorted out as before. With a little encouragement from a friend I sussed that where the two mottor block connectors attach to the main board they short out with each other. We deduced that if I bypassed the main board connections and hardwired the two motor blocks together then we would avoid the short circuit. Also, applying track power to the two track positive and negative decoder pins on the main board (decoder interface board), then I could obtain sound as well as movement. Unfortunately, I was by this time greatly disillusioned with the whole thing and left it in pieces for several months.

Today, longing for a new project, I once again revisited this catastrophe. I hardwired the two motor blocks together (for the moment I am only interested in analogue operation). I then supplied track power to the track power decoder interface pins on the main board and eventually had success. The loco was reassembled and is now running satisfactorily on analogue.

In time I will disassemble and rewire to fit a Massoth XL decoder and hopefully achieve what I set out to do nearly six months ago. This whole episode has really tested my reserves. I believed it would be a simple install as the unit is decoder interface ready and would just need a decoder fitted to get digital control. Alas, all is not as it seems. When I am happy with the loco I will obtain a decoder and revisit this abomination.
 
Ross,
the LGB sound board is a stock replacement part. Theoretically, since the Uintah and Sumpter Valley Mallets are mechanically similar (chassis and drive blocks), the board should have been a direct install. What has stumped me is that simply plugging the motor block four pin connectors into the replacement board causes a short circuit. When the same connectors are attached to the original Uintah main board the operation is fine. Even a replacement board caused a short circuit.

I did continuity checks on both replacement main boards and there is a direct short where the drive connector blocks are fitted. One board maybe a fault but two boards with the same problem is pushing reality a bit.

My workaround will provide a solution but not the easy solution I originally intended.
 
Have you been a little to 'clever' here? - No offence meant.

The motor block at either end may well be opposite ways round, so track + from one needs to go to track - of the other. - This caught me out on a loco (diesel I think) when I first started wiring decoders.
We tend to plug the originals 'as was' and all is well.. We then very carefully check we have the wiring 'right', but if the motor blocks are 180 degrees out from each other, then what should be right is wrong. - You know what I mean! ;)
 
Phil,
As stated in a previous response from me, (quote: "I did continuity checks on both replacement main boards and there is a direct short where the drive connector blocks are fitted." end quote). On the original Uintah main board the track pins are not electrically interconnected, thus operation is fine.

Even without the drive connector blocks fitted to the board, the track designated pins on the board are interconnected so that a short circuit occurring is guaranteed.
 
I revisited the loco today. I decided to wire the loco so that installing a decoder in the future will be easier. When I wired it yesterday it was analogue friendly but not really suited to fitting a decoder.

I noted that after about ten minutes running the sound would shutdown and then slowly reinstate after a minute or so, firstly with very low volume and then later up to full volume several minutes later.

Because I am powering the main board and subsequently the separate sound board using the track power decoder interface pins I deduced that maybe the electrics were thinking that they were in 'digital' mode. When running digitally, the #1 DIP switch on the sound board must be turned to the 'OFF' position. I thought that this would deactivate the onboard capacitor pack. The loco has been running now for about half an hour with no problems. Surprisingly the capacitors are still active. I have no idea what turning off DIP switch #1 does, but it does seem to have corrected the sound shutdown problem.

Edit: one issue with directly powering the motors is that the natural 'delayed starting voltage' factored in the stock main board electrics is not active and so moving off slowly the loco will move prior any sound.

In hindsight I should have simply dumped all the electrics and fitted a sound decoder, but I was fond of the Sumpter Valley Mallett factory sound.
 
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