Kato/Atlas GP35 and TCS CN decoder (won't fit)

[Tom4884]

I am converting an older Atlas GP35 using a TCS CN decoder and have run into a roadblock.   After doing all the required milling so the boards have clearance from the frame, the TCS board is a little thicker than the original light board and will not fully seat in the notches on the frame.  What is the best way to open the slot just enough to seat the board while still maintaining good electrical connections and not breaking anything?   Thank for any assistance,

Tom

[C855B]

DO NOT pry on the notches! You will break them off! That white metal is awfully brittle. (Yes. Experience.)

This is the first time I've read of problems with the CN boards being too thick. I've done several, and they're always been too thin, and I tin the contacts for a soft metal surface to wedge into the slots. All I can suggest is a very thin jeweler's file for the notches. Maybe an emery board will work, too, then follow-up with solder on the board contacts.

[MK]

That's interesting.  I've never had a decoder where the board is too thick.  Always too thin or just right.  Like Mike said, file, not pry!

[Bendtracker1]

I've not heard of a board being too thick either?  I would try thinning the board by scraping or sanding the bottom sides of the pads rather than the frames.  That way if the board gets too thin, then you can simply add a pillow of solder to to the top pads to thicken it up so it fits snug in the frame.

[peteski]

The copper traces/pads on the PC board are very thin (probably around 0.001")  Not much to file/sand until you totally remove them.

[C855B]

The copper traces/pads on the PC board are very thin (probably around 0.001")  Not much to file/sand until you totally remove them.

 That's right. DO NOT file or sand the corners of the circuit board! Either side!

[MK]

Wait!  It just occurred to me that the board is probably too WIDE to fit into the slots.  I just installed two of these into RS-1's recently.  I too could not get them to go into the slots.  They were too WIDE and I had to file the edges slightly to make the boards narrower.

It's it too narrow or too thick?  Either situation would prevent insertion.

[jagged ben]

This was a problem for me with Digitrax boards for Intermountain tunnel motors.  I ended up taking my dremel to them with the tiniest milling bit I had.  I have the flexible shaft, I should note.  Do I recommend this method?  Not necessarily, you can easily overdo it if you're not careful.  I managed it, but it was a bit nerve wracking.

[C855B]

I'm going to try to answer this directly tomorrow. I have an unconverted older GP35 and a bunch of CN and GP-CN decoders in the stash, so I will take a look.

[C855B]

I'm going to try to answer this directly tomorrow. I have an unconverted older GP35 and a bunch of CN and CN-GP decoders in the stash, so I will take a look.

It turns out that I don't have any CN decoders, just a whole bunch of CN-GP. They appear from TCS's illustrations to be different sizes. Now I tried to fit a CN-GP into a GP35, and it would work, but only with some milling of the frame under the circuit boards.

@Tom4884 , is the problem we're having here that the board will only go in at an angle because the components underneath the board keep it from sitting flat? That's what I encountered with the CN-GP.

I'm going to order a handful of CN decoders tonight since I have more GP35s to convert than I thought, so if you can wait a week I can give a more precise answer to your dilemma.

[Tom4884]

I am happy to report that I was able to successfully install the CN decoder in my GP35.  In the TCS manual on installing CN or CN-GP decoders it states that inserting a flat screwdriver into the slot and "GENTLY" prying upward you can open the slot enough to get the decoder to fully seat, which with some trepidation and extreme care is what I did.  I have installed dozens of these in SD45s, SD40s, and a number of GPs,  and it's the first time I had this problem.  As several stated it's much more common for it to be too loose.   Thanks for all the help and suggestions,

Tom