# MTH Big Boy - Fuse protection for rear power board



## Rayman4449 (Jan 2, 2008)

I wanted to share that my original testing was successful in correctly selecting the fuse amperage (of 3 amps) for this preventive measure to protect the rear engine set power traces from burn out.  

http://www.rayman4449.dynip.com/MTH...wer pickup wires to protect from short damage 

In this modification I added a fuse holder and a 3 amp fuse inline in the positive and negative wires that run from the front and rear engine power pickups. 3 amps was about the max that narrow trace could take before cooking the board sealant (~4amps) and not much more than that the trace would blow. At three amps that trace is hot to the touch. 

From the last train show I must have had a temp short of a front engine slider as one fuse was blown and after replacing it, I had continuity between the front and rear sets which means it protected the trace likely to blow under a short. 

This is good news as it's an easy mod and can save headaches later on. 

Keep it on the rails... 


Raymond


----------



## bud (Jan 10, 2008)

Sounds good except I went a different route, I added heavy jumper wires across the board bypassing the puny lands. 
Now if it jumps the track my track fuse blows and does not blow the board. 
Bud


----------



## Rayman4449 (Jan 2, 2008)

Anyone considering doing this needs to remember there is very little clearance space between the top of the board and the axles. Be carefuly of pinching wires or exposing them to rubbing on the axles. If you run the jumper as Bud's done you will want to run jumpers direct from the end board connection point to the sider connection and another jumper from there to the wheel power pickups and from there to the rear connection points. Otherwise you will still be relying on existing unprotected circuit paths. 

Also note that by using the jumpers on the rear the weak point will then be on the front board paths between the slider pickup point and the end board connection. You would likely want to add jumpers there too. This was why I just added fuses. Either way should ensure you have no future problems.  


Raymond


----------

