My curiosity got the best of me, so I went down to the layout and soldered the pick up wires to the copper strips on the front trucks, after removing those plastic clips.
Nothing!
The front trucks still do not work. With the rear trucks off the rails, the motor stops spinning.
Foolish me, but I am convinced that the problem is with the decoder.
I suppose the next step would be to desolder all four pick up wires from the decoder teminals and reverse them, connecting the front pick up wires to the rear decoder terminals and the rear pick up wires to the front decoder terminals. If the rear trucks no longer were working but the front trucks were working, that would confirm a problem with the front terminals on the decoder. Agreed?
Frank, that is a good point, and I have wondered about that. The source of the continuity at that point is the pointed ends of the axles. That is a pretty small contact point, so I wonder whether that could be the problem.
With the rear trucks off the rails, and the motor not spinning, I have applied pressure to the side frames of the trucks to see if better contact could be made with the wheels, but no luck.
Is it possible to solder jumper wires between the rear truck and the front truck? Then solder these to the decoder terminals for the rear truck. This is the route that I would go just to see if everything worked.
It is possible but unlikely that the decoder traces from on end to the other is broken. I would solder one end to the other with a piece of decoder wire. This in essence is extending the front truck pickups to the rear truck pickups. Cold solder joints can be the main problem.
I don’t have Genesis F7’s,but I do have three SD75m’s and the pick-up should be the same,except of course for the third axle, but the whole end of the axle picks up power from the bar,not just the pointed end,they suggest putting a light drop of oil,where the axle goes into the bar and get rid of the wire locks and solder the wire to the bar.
I agree with soldering all wire connections, but don’t put any oil in a location designed for electrical continuity (unless of course you use electrically conductive lubricant, and even then I wouldn’t recommend it).
I’ve had more than a few engines develop poor electrical pick up, and the problem was ultimately found to be lubricants in the axle contact strip causing a contact problem. Dry the axle tips and ream out the holes in the contact strip with round wooden toothpicks until no more black showed and the problem went away.
Below is a couple paragraphs from another thread I copied and pasted here that might be your problem. It sure fixed all my problems with my 6 Genesis units I have.
The wheelsets have a split axle with a plastic gear in the middle. The axle ends extend into a metal bearing plate in the sideframes. This bearing plate should transfer both the electrical current and weight of the locomotive between the wheels and the trucks. The wheelsets fit into a gear tower and are held in place with a plastic plate that snaps onto the bottom of the truck. The two plastic sides of the gear tower have slots for the axles. The problem is that the slots are NOT DEEP ENOUGH. The plastic part of the axles rubs on the top of the plastic gear tower slots, causing the axles ends to “float” in the bearing plates resulting in intermittent electrical contact.
The solution: Remove the sideframes and wheelsets. Take a small round file and file the axle slots in the gear tower to make them deeper. (You might want to completely disassemble the trucks to do this. I didn’t bother since a few plastic filings shouldn’t be too harmful.) Once this was done and the trucks were reassembled the problem was GONE! This fixed all my Genesis F-units.
It states,putting a drop of oil,right in my maintenance instructions,that I got with all three of my Genesis SD70/75M’s,from Athearn,sometimes,it does not hurt,to read those things,once in awhile. The pick-up,is the same as the F7’s,except, again for the third axle.
Frank, I wasn’t challenging your statement, but I was asking who “they” were. I now assume that you meant Athearn.
Interestingly, there is no such statement in my Athearn Genesis F7 Santa Fe owner’s manual about oiling the axles or the slots that they fit in on the trucks.
I am pretty convinced it’s NOT the decoder. If the decoder was bad, it wouldn’t run at all The only possible way it could be the decoder in this case is if one of those end to end traces is somehow cut, somewhere between where the front truck wires connect and where the rest of the circuit taps off this power to operate the decoder. Not too likely, at least by accident. And if this were the case, there would be no continuity betwwen the left rear wheel and left front wheel, or right rear wheel and right front wheel, as those decoder traces sit right in the middle of all that. I believe you have a pickup problem between the wheel and the pickup itself, where you have just soldered the wires.
Do you have a headlight hooked up? Does it go out when you lift the rear truck off and the motor stops? Witht he rear truck insulated from the track, try wiggling the front truck around and see if the light flickers on or the motor gives a little jump - that would pretty m,uch prove intermittant pickup.
I desoldered all four pick up wires from the decoder teminals and reverse them, connecting the front pick up wires to the rear decoder terminals and the rear pick up wires to the front decoder terminals.
Once I did that, the front trucks were working and the rear trucks were not working.
So, that tells me that the problem is one or both of the front terminals on the decoder.
There is power being picked up by all four trucks and delivered to the decoder, but the front terminals of the decoder are not sending power to the motor.
Am I testing and reasoning correctly, or am I missing something?
If that’s the case, I would forget about trying to diagnose what the problem is. Re-install the truck wires where they should go, then solder a jumper wire on both sides from the front tab to the rear tab.
Do you have a meter? I have a DA-SR in front of me with no wires attached. The back of the decoder defines the right rail conections as the side of the decoder with the two motor connections. Obviously the other side of the decoder is where the left rail connects.
Disconnect the wires to the decoder.
With the meter set at an ohms value, connect one meter lead to the front right rail connection point and the other lead to the rear left rail connection point. Your meter should read zero ohms. This is as it should be because the front and rear connection points are connected on the back side of the decoder with a large connecting trace as Randy mentioned previously.
Now re-connect the meter leads to the left side connection points. You should again get zero ohms.
I also connected the meter to the left and right rail connection points on one end of the decoder. With the meter set at 20K ohms or less, I read an open circuit, meaning that there was sufficient resistance from the decoder components to show an open circuit. I did check across these same points with a higher resistance meter setting. With the meter reset to 200K ohms, I read 63 ohms from the left to right rail connections. I reconnected the meter to the terminals on the other end, and got basically the same values.
I believe that the only thing you can check on the decoder is the front to back continuity. If you have that, then in my opinion there is a decoder fault. What I can’t tell from looking at the decoder is how the board components connect to the two large traces. I would think that the two traces are the main connection points and everything is in series with them. But I suppose it is also possible that there is some sort of parallel circuit where there are duplicate connections from each of the traces so the there is redundancy in case one end or the other of the decoder goes bad.
Any holes in the board have plating through them to connect front traces to back traces - even the ones where you connect the truck wires. You should never drill through these holes to enlarge them to fit a wire through.
Just a thought as to maybe why one end is getting power and the other isn’t. If the through hole plating is damaged, you will lose your connection as well. Might not hurt to test each pad top to bottom with the meter.
Frank, the reason that the 12 volt incandescent bulb lit on the front decoder terminals with the rear trucks lifted off the rails was because there was power on those front decoder terminals. That was the indication that I was getting all along. This is clearly a decoder problem where the power from the front terminals is not reaching the motor.
Incidentally, I did a Google search and it is interesting, though not surprising, to me that others have experienced similar problems with the DA-SR decoder. There is more than one complaint out there about the front trucks appearing not to pick up power to the decoder only to discover that there is power at the front decoder terminals.