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I have several MTH locos and few RailKing that perform without a hitch passing through the accessory section, but my GP-38s and GP-40s will get stuck at slow speeds. At through-freight speed, they kind of blip and keep on going but at switching speeds, they die out. If I move an inch or 2 either direction by hand, they will fire back up. Any ideas??

The accessory section is triggering an 18VAC relay for signals, which works rather well. I'd hate to give up on it.

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Are you using insulating track sections?  Are these premier locos with 2/3 rail capability?  If so, the MTH locos with the plastic baseplate on the power truck have problems with continuity between the wheelset and truck block, and with the 2/3 rail switch.  Check continuity between wheels on opposite sides and opposite trucks.  If the former, 0.005” shims are installed between the bronze bearing and truck block.

Railking diesels had some problems (rare, but I seen a few) where the coating on the truck block interfered with the ground path through the axle bearing.  Continuity checks will confirm this.

Hi Jon,



Yes, they are Premier locos with 2/3 switch. . I have 3 Dash-8s and they don't do it. Yes, its a Fastrack insulated section. I'll have to take a night and check the continuity. May be later this week. I'm just trying to get my head around it. These are all new locos within the past year, but just out of warrantee (of course!) . I don't think the problem showed up until I installed the insulate track sections a few weeks ago.  

We noticed this problem on the test track at MTH where a route had only one outside rail grounded.  Excessive play in the bronze bearing to the truck block or a bad 2/3 rail switch.  Shimming corrected it 99% of the time. K&S sells some shim stock that works. Others have found material in Hobby Lobby.  Cut and shaped into a “U” to cradle the bearing eliminates the play.

Remove the pickups and the 3 or 4 small black screws, lift off the plastic baseplate to access the wheel sets. Easy-peasy.

@Jon G posted:

We noticed this problem on the test track at MTH where a route had only one outside rail grounded.  Excessive play in the bronze bearing to the truck block or a bad 2/3 rail switch.  Shimming corrected it 99% of the time. K&S sells some shim stock that works. Others have found material in Hobby Lobby.  Cut and shaped into a “U” to cradle the bearing eliminates the play.

Remove the pickups and the 3 or 4 small black screws, lift off the plastic baseplate to access the wheel sets. Easy-peasy.

Sounds great. Images?

I took this 6 month old GP-40 apart to establish a baseline. I haven't meddled with anything, but wanted to document the wheel arrangement before I took my others apart. Should I have continuity left to right and front to back amongst all the outer wheels??

Or should I go straight to the 2/3 switch?

I did shunt the insulated track section with a jumper and the loco ran right across it, so I'm thinking something is up with the outer wheel

Thanks Guys!

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The wheelset axles are split and insulated in the center.  You should have close to zero resistance from side to side and truck to truck, but the plastic baseplate has to be in place as it has the jumpers to pick up ground from the insulated bearings.  If resistance is high (not infinite), my guess would be to shim the bronze bearings first.  If resistance is infinite or very high, check the switch.  When assembled, if the switch is clamped crooked, it mashes the contacts so they don’t make good internal connection.  The black wire connects to the truck block which picks up ground from the bronze bearings, the brown wire picks up ground from the insulated bearings, the red wire is the center pickup.  Connect to brown and black wires together to tie both sides of the wheel sets together if you want to bypass the switch.

Last edited by Jon G

Jon,

Taking advantage of the dank New England weather, I finally tackled the 2/3 wire dilemma. Following you recipe, I eliminated the 2/3 switch sucessfully on my first patient. I went straight for the switch over the wheels, have viewed it as a "final cure".

I took the second GP-40 apart, expecting to do the same, but much to my chagrin, dicovered melted wires. See attached pics. It seems to be only these 2 wires, one red and one black, that are affected. Any idea what would have caused that?? I'm thinking it was stalled out across across a with or something like that....or under voltage??

Happy New Year, and Thanks!!

Bob

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