Loose DCC board


S

steveparkinson

Member
Installed a TCS decoder (ALD4) in an Atlas SD-60 and it's got an intermittent connection. When I install the shell it sometimes doesn't work once put on the track, taking the shell off and wiggling the decoder board usually fixes the problem until next time.

My question is, I've read you can solder some decoder to make better connections. If so which would I solder on this particular locomotive? Photos below

A - tabs coming through the board?

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Or B the 4 tabs at the ends of the decoder that touch the shell?

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It's my first one with this problem so I want to make sure before I do anything. Gently pushing down on the decoder at each end does make the light go on and off when it's on track.

Thanks
Steve



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In the first photo it looks like the one tab by your pointer is broken off or missing. Is it making intermittent contact on the side of the slot?

Joe
 
Think it's there, just pointed in towards the center making it difficult to see but I'll double check it in a few when I get back home.


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It's there, it did look shorter than the other. I made sure it was bent towards the board.

Tried putting a piece of kapton tape between the fwd end of the board and frame to keep it snug. I'll see if that makes a difference.

06f3e7caf39b1cc0fef52e835bca479c.jpg


Thanks
Steve


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don't solder those directly if you try, you will have too much fun trying to remove the board when you have to. Get some small wire, solder first to the board then loop it to the tab soldering it. You could have the board quasi-off then after soldering, remount the board with wires on.
 
Thanks for the tip, makes perfect sense if I ever decide to remove the board. Which sets of connections would cause the loose connections though? I'd prefer not to do any soldering if I can avoid it. Is it ok to solder all six connections if I needed too?


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steveparkinson said:
...My question is, I've read you can solder some decoder to make better connections. If so which would I solder on this particular locomotive? Photos below

A - tabs coming through the board?
...
Or B the 4 tabs at the ends of the decoder that touch the shell?
...
Click to expand...

A - You have two options here - 1. re-install the decoder without pulling the tabs through the board - the tabs will press against the pads on the bottom of the decoder - this is actually how these decoders were originally designed and how the DC lightboard works. I believe they added the slots because some people do prefer to solder those tabs. 2. If you do leave them pulled through the slots, then you probably should solder them.

B - you would not want to solder these to the frame, but if they fit loose you can remove the decoder and add a dab of solder to the pads to make them fit tighter in the frame.

steveparkinson said:
...Which sets of connections would cause the loose connections though?.
Click to expand...

If the loco won't run, but the lights will come on, then it's the tabs in the middle (they supply power from the decoder to the motor). If the lights won't come on then it's the tabs on the ends of the board (they supply power to the decoder itself).
 
Robert, thanks that helps a lot. Should be able to pinpoint the problem better now. I'll check these and see which is required.


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I would get some alcohol and q tips and clean your connections, put your decoder together shell off and put it on the track and watch the performance. If there are bottom touch connectors touching the decoder pads to make the connections, clean those, if these tabs are reaching thru the holes and are the only thing making the connection this may be where your intermittent problem could be, fiddling with the shell may wobble the decoder making/breaking a connection. But I would presume directly below that hole is a touch connector?

the tabs in the middle look like the go right to the motor, what you want is to prod-bend them down carefully, if you break, solder time with mini-wire. The edge tabs are touch connecting the split frame for power at 2 points each. Call me goofy but a dab of Rail-Zip on the contact points could help. Perhaps keep oxygenation off that causes corroding. If the decoder needs upper pressure for the contacts for those side touch conects, a mini-formed piece of paper underneath the decoder to give some mini-force upwards may aid the touch connection. A little thin paper or index card stock cut-shaped inserted.
 
Ok removed decoder and cleaned all contact points with alcohol and reinstalled. Inserted some kapton tape below the bottom of the decoder and the frame to push it up snug where the top points of the decoder meet the frame. Middle tabs come through and touch but now I get nothing but the light in fwd. I can turn off the light and back on but it doesn't do anything when I change direction or apply power to the locomotive. Tried resetting the decoder in programming mode too and nothing??


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steveparkinson said:
...I get nothing but the light in fwd. I can turn off the light and back on but it doesn't do anything when I change direction or apply power to the locomotive...
Click to expand...

That means the middle tabs are not making good contact.

steveparkinson said:
...Middle tabs come through and touch...
Click to expand...

Again, I would either leave the tabs under the decoder pressing against the pads on the bottom (I have several Atlas locos done like this), or solder them if you are going to leave them poking through the slots.
 
yes, with the decoder out, you bend them tabs down, if there is a touch pad underneath, they should touch that and there should be natural pressure by the tab to make constant contact, too much repeated bending you may snap them off.
 
Ok so I tried this before pulling it out again just to see if this changes anything or the recommendations given.

I connected a pair of alligator clips to my multimeter leads and put a piece of conductive wire in the alligator clips and checked continuity between each pad and the frame and it read good, did the same with the motor tabs and the pad surrounding it and it reads good - all had good readings (about 1-3 ohms). That was all with the loco on my bench, no power applied to loco.


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If you have a jewelers loupe or a very strong magnifying glass look at all the soldered connections on both sides of the board while very gently and minutely flexing the board and see if you can see any movement at all of the solder connections. You may have a broken or loose solder joint.
 
you have multi-meter? good. Back on the track, power it, turn on forward, touch meter on decoder (tab) pads (not the tabs) check for voltage. (power?) touch the tabs (power?) touch one side tab, other side pad..(power?) reverse test points pad tab....(power?) remove from track/power...go to OHms, test tab/pad one side...test/pad other side for continuity.
 
josephbw said:
If you have a jewelers loupe or a very strong magnifying glass look at all the soldered connections on both sides of the board while very gently and minutely flexing the board and see if you can see any movement at all of the solder connections. You may have a broken or loose solder joint.
Click to expand...

I'll have to borrow/buy a magnifying glass as I don't have one right now at the house. Can check the connections once I have one and remove the board again.


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dinwitty said:
you have multi-meter? good. Back on the track, power it, turn on forward, touch meter on decoder (tab) pads (not the tabs) check for voltage. (power?) touch the tabs (power?) touch one side tab, other side pad..(power?) reverse test points pad tab....(power?) remove from track/power...go to OHms, test tab/pad one side...test/pad other side for continuity.
Click to expand...

Just to make sure I understand....

1 power loco on track in forward
2 next check for DC power on motor tab pads
3 next check for DC power on motor tabs
4 next check for DC power on one tab and opposite pad
5 next check for DC power on other tab and other pad
6 remove from track and check each tab to its pad for continuity


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