LGB Mikado lighting Acting Up

[ALCOMOTIVE]

After replacing the smoke unit in my LGB Mikado, I noticed the headlight wasn’t coming on. Upon further inspection, it seems that the previous owner jammed the bulb in so far it was entirely stuck in there, and the connections between the headlight base and leads were frayed. After replacing the bulb, base, and leads - nothing. Even the tender light won’t come on. According to my multimeter, there’s only about 1v output from the board, compared to the intended 5-6v. I’m guessing something must’ve shorted due to the above mentioned frayed wire at the headlight base. Any suggestions/advice?

Thanks in advance,

-Noah

 

[ALCOMOTIVE]

Update: I am now seeing sufficient Voltage at on the board, but no lights. The light works fine when the leads are connected to the 5v smoke plugs, just not when they’re connected to their own plugs. Not sure what to make of that.

 

[LGB333]

Update: I am now seeing sufficient Voltage at on the board, but no lights. The light works fine when the leads are connected to the 5v smoke plugs, just not when they’re connected to their own plugs. Not sure what to make of that.

That's any interesting situation. I assume you are operating in DC analog power, not DCC. The reason I ask is that DCC powered locomotives are a lot more touchy to defects in electrical devices.....DC is more forgiving. For example, I was converting an older LGB Crocodile to DCC sound and found a short was occuring when the locomotive went in the forward direction but not the reverse direction.......the motors would slow down. I worked an hour trying to find what was causing the short and accidently discovered one of the front headlight's bulb base was the short.......the two wires' solder joints were touching each other on that base. So, as you discovered already, make sure all your light fixtures and wiring are properly configured and no short exists.

I also wonder if the defect you found in the lights wiring may have damaged the lighting function in the main circuit board. But one of our electrical engineer hobbyists may have some additional insight into your lights issue.

 

[ALCOMOTIVE]

The light works fine when I plug it into the smoke unit outlet, suggesting that the light outlets on the board are the problem. What’s weird is that the headlight outlets still show 6V on the meter. I think your probably correct in that a short probably messed up the whole lighting circuit. The question now is how do I fix that?

That's any interesting situation. I assume you are operating in DC analog power, not DCC. The reason I ask is that DCC powered locomotives are a lot more touchy to defects in electrical devices.....DC is more forgiving. For example, I was converting an older LGB Crocodile to DCC sound and found a short was occuring when the locomotive went in the forward direction but not the reverse direction.......the motors would slow down. I worked an hour trying to find what was causing the short and accidently discovered one of the front headlight's bulb base was the short.......the two wires' solder joints were touching each other on that base. So, as you discovered already, make sure all your light fixtures and wiring are properly configured and no short exists.

I also wonder if the defect you found in the lights wiring may have damaged the lighting function in the main circuit board. But one of our electrical engineer hobbyists may have some additional insight into your lights issue.

 

[PhilP]

The problem is that a meter presents a very high impedance, so a tiny current will show the voltage.

If it is a physical problem, you will need to use a different function output.
Or find someone who can repair the decoder. - Difficult.

It could be one (or more) CV's are scrambled, but I doubt it.

PhilP

 

[dunnyrail]

The problem is that a meter presents a very high impedance, so a tiny current will show the voltage.

If it is a physical problem, you will need to use a different function output.
Or find someone who can repair the decoder. - Difficult.

It could be one (or more) CV's are scrambled, but I doubt it.

PhilP

Good point Phil, if there is only one output left forward and reverse changing of lighting could be resolved by fitting LED’s and using Diodes to block the unwanted positive output at whatever end.

 

[ALCOMOTIVE]

The problem is that a meter presents a very high impedance, so a tiny current will show the voltage.

If it is a physical problem, you will need to use a different function output.
Or find someone who can repair the decoder. - Difficult.

It could be one (or more) CV's are scrambled, but I doubt it.

PhilP

My Mikado is still analogue. If it’s a physical issue with the board I can get a replacement, I just won’t be happy about it. I’d prefer to fix it myself, but if I can’t then I won’t.

The problem is that a meter presents a very high impedance, so a tiny current will show the voltage.

If it is a physical problem, you will need to use a different function output.
Or find someone who can repair the decoder. - Difficult.

It could be one (or more) CV's are scrambled, but I doubt it.

PhilP

 

[PhilP]

My Mikado is still analogue. If it’s a physical issue with the board I can get a replacement, I just won’t be happy about it. I’d prefer to fix it myself, but if I can’t then I won’t.

If you have an analogue board, then I would think the short circuit will have blown one of the diodes. - Possibly a transistor?

If it is not obvious from a visual inspection, it should be relatively easy to check the operation of the diodes with a meter. - You would probably have to lift one end of each diode to test it.

PhilP

 

[LGB333]

My Mikado is still analogue. If it’s a physical issue with the board I can get a replacement, I just won’t be happy about it. I’d prefer to fix it myself, but if I can’t then I won’t.

The LGB Mikados were produced by the original LGB company during 2002 - 2005 timeframe and the MTS/DCC/DC Onboard Sound Decoders are no longer produced, so replacing your existing board is not a viable option.......you might find a used on someplace like eBay. So, it's better to do a workaround fix using a unused terminal on your existing decoder board, or tapping into an existing terminal using diodes, resistors or voltage regulator to control the voltage to your light. Of course, you could change all your light bulbs to Massoth 19v. bulbs and use track power for the lights. Sometimes on DCC sound conversions I'll change out the 5v. light bulbs or 5v. smokers to the higher voltage versions so I don't have to fiddle with dimming down the voltage on the decoder.

 

[ALCOMOTIVE]

The LGB Mikados were produced by the original LGB company during 2002 - 2005 timeframe and the MTS/DCC/DC Onboard Sound Decoders are no longer produced, so replacing your existing board is not a viable option.......you might find a used on someplace like eBay. So, it's better to do a workaround fix using a unused terminal on your existing decoder board, or tapping into an existing terminal using diodes, resistors or voltage regulator to control the voltage to your light. Of course, you could change all your light bulbs to Massoth 19v. bulbs and use track power for the lights. Sometimes on DCC sound conversions I'll change out the 5v. light bulbs or 5v. smokers to the higher voltage versions so I don't have to fiddle with dimming down the voltage on the decoder.

Attempting to replace the opened diode only made things worse- fortunately I was able to find another board on eBay, which works out nicely since it gives me a Spare board to mess with and try diffirent mods. I want to rewire the switch so that it only engages the motor at position 4, and engages all other features at position 3. Then, I plan to add a Massoth pulsed analogue unit, which would benefit from being run at full power before the motor engages.