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Excessive clearance could lead to SD card being eaten


Tjoppen

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Today I noticed that SD cards can slip into the Harmony cartridge itself if you're not careful. I've attached a staged picture demonstrating the issue. I'm not sure how hard the card would be to get out if it does slip in - I don't feel like experimenting..

I'm not sure if mine is the only one with this potential issue, but I thought I'd bring it up along with some suggestions on how to remedy it:

 

During manufacturing:

 

* Use a Dremel-like tool when making the cut-out, making sure to only take off as much/deeply as needed for the connectors to poke through

* Apply hot glue or some kind of resin to shrink the opening if it's too big, preferably in a way that doesn't leave the cartridge permanently sealed (repairs, mods)

 

On the user side:

 

* Insert and glue a sufficiently thick piece of cardboard in place

(* Hot glue - be very careful due to risk of heat damage and connectors being covered)

* Always be careful :)

 

This is the only real issue I've discovered so far, apart from the FTDI chip's driver sometimes refusing to re-mount when the USB cable is inserted, which is probably unrelated to the Harmony itself. This is fixable by running "stty -F /dev/ttyUSB0 115200" for any search engines coming by here.

post-28396-0-21918900-1332847169_thumb.jpg

Edited by Tjoppen
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Yes i feel your pain i trusted my son to put the sd card in mine.

And wouldnt you know it he pushed it all the way down .

I couldnt understand why i was getting a blank sreen untill i looked closely at it.

I just used a paperclip and fished it out but i havent let my son do that again cuz it was kind of a pain fishing it out.

 

Scott

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Yes, it's happened to me before. However, the fix is not trivial. It's not just a matter of cutting a smaller hole.

 

Harmony is contructed of two boards soldered together. The reason this was done was for ecomony of scale for Melody boards and the Harmony cart (they share a common board) so I could have a large quantity of this one board professionally assembled to keep costs down.

 

Now, although I have a jig to attach these two boards, there is considerable tolerance as to how these boards fit together, and the shells are not all made equally (some have the screw mast in a slightly different place, some shells are made of harder plastic, some hold the main board better than others) and that coupled with the card insertion, the board actually can move inside the shell. All this together means the hole must be wider than it seems like it needs to me.

 

Furthermore, some clearance is needed above the card slot because you need to guide the screw mast into the hole in the board while putting the shell together. Some shells simply will not close unless you insert a thin tool in while the shell is snapped together to help slide the screw mast into the hole.

 

Engineering is often not just elegant with exact solutions, as sometimes you are minimizing a bunch of less-than-ideal solutions.

 

Someday I plan to produce a new Harmony with just a single board and a new, custom shell. This will be available as a special edition, and will cost more due to the smaller quantity and increased material cost, but this will not have any of the issues with fitment or anything else that some regular Harmony carts have.

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How about putting a square of black foam tape on the sd slot casing, prior to assembly?

If I could still get the tool in without damaging the foam, that could work, but perhaps it could be done after assembly. If that is the case, those who already own a Harmony could try it as well.

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When I first got my harmony cart, I was a little surprised and disappointed with how large that hole was, but I understood why. I figured it was just so much faster and easier to cut to those points than to try to be exact. If you're dealing with just a couple of carts, it wouldn't be a big issue, but when you're producing a lot, I supposed he needed to go the faster/easier route. I didn't even know about the other reasons stated by batari above.

 

Here was my solution:

post-9364-0-43773800-1333474264_thumb.jpg

 

You can see from this pic, there is absolutely no excess clearance. I cut a new shell to fit exactly. :)

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I plan to put an end label on it. I just haven't decided on a design yet.

 

I put the original label back on. I just warmed it with a blow dryer on low setting, lifted a corner with a hobby knife, carefully peeled it off, and set it on wax paper until I was ready to stick it back on. The glue on those labels is really good btw. I'd really like to know what brand of sticker paper was used cause the ones I had in the past were no good.

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  • 4 weeks later...

Simple solution--go to a hobby store and get a piece of thin styrene stock. Measure and cut a piece to fit in the depression where the end label would be, then measure and cut two holes--one for the SD slot and one for the USB connector. You could paint it with Krylon Fusion to match the cartridge case's color or use a marker to darken the styrene. Attach with contact cement and you're done.

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