Ultimate64 – Cartridge slot problem

Before you start to read this post I know that Gideon has tried to obtain better quality (card edge) connectors from several suppliers. So far no luck. Gideon put very much effort into the Ultimate 64 boards. He tried (and did) to give us a Commodore 64 replacement board that is future proof, which I appreciate enormously!! So don’t read this post as a negative post!

The problem that can occur

Some cartridge slots (egde connector) on the Ultimate 64 can’t handle cartridges without V-shape beveled PCB’s, so be carefull with those carts, they can damage (bend) the pins of the edge connector.

Bended pins:


Cartridge PCB thinkness & bevel does it matter ?

Cartridge Thinkness (mm) PCB Edge
Mssiah 1.60
MS Pacman 1.75
Ultimate 1541-II 1.60
Kerberos 1.50
The Final Cartridge III 1.55
Action Replay 1.60
Power Cartridge 1.60
Sound Expander 1.70

I tested the above mentioned cartridges and I experienced resistance on all the cartridges without a round of V-shape PCB bevel. In my opinion it has everything to do with cartridges that are not beveled and not especially the thinkness of the PCB.

If we compare the Sound Expander cartridge (1.70mm/V-Shape bevel) and Mssiah (1,60mm/straight, no bevel), I can insert the Sound Expander cart pretty smooth, but to insert the Mssiah cart I have to apply more pressure, keep in mind that this cart is less thick.

Try to avoid damage

Check PCB bevel

If you look into the cartridge sideways, and feel the pcb edge, does it feel edgy of a bit smooth ?

Don’t try to insert the cartridge into the U64 if the edge (no bevel) looks like:

You can try to insert the cartridge gentle into the slot without excessive force if the edge (V-Shape bevel) looks like:

I’m not so sure about this kind (Rounded) of bevel:

It’s your own call to try it! I can’t be held responsible for damaging the slot!!


The way I insert the carts into the cartridge slot

Try to insert the cartridge into the cartridge slot like this. The presure points are spaced more equaly.


Difference between edge connectors

The edge connector that’s used on the Ultimate64:

The edge connector that’s used on the original Commodore 64:

Damaged edge connector? Replace it..


I harvested an edge connector from a scrap board and used it to replace the one on the U64 board.

To remove the U64 edge connector you first have to remove the metal cage.

After that I advise to add fresh solder with lead to all the pins before desolder them, because the U64 edge connector is soldered with solder without lead and that’s quite hard to remove.

CAUTION: To minimise health hazards when using solder with lead & flux, use a fume extractor!




Where to get those edge connectors



17 thoughts to “Ultimate64 – Cartridge slot problem”

  1. Quality research, thanks! Beveling the cart PCB edges with a file has been known to help in some cases too.

  2. I’ve been warning people time and time again about cheap cartridges with no beveling and no gold plating. They can wreck a cart port connector.

    Better believe it.

  3. The cartridge port connector included with the Ultimate-64 is made by Hirose. The original cartridge port connectors of the C64/C64c/C128 were made by EDAC and are still available on Digikey.

    1. I will update this post ASAP with new information about the right edge connectors, which Gideon now uses on the new U64 boards.
      Thanks for your feedback!

    2. Hi,where is the part number on Digikey? for the cartridge port connector on C64.

  4. I took a peek at the Ultimate64 Elite that I have and it doesn’t look like either of those. It isn’t nearly as blunt as the first one, and not rounded like the OG one. It ramps back at a gentle slope. I don’t know what it was built, I’d have to pull open the case (breadbin) I guess.

  5. Fine gentleman Nadeem Yazdani aka donnydarko19 sells a bunch of C64/C128 cartridges on eBay and NONE of them have gold plating or beveling. All have HASL on the edge connector.

    He recently purchased a few of my products on eBay, apparently solely for the purpose of leaving me a negative feedback. I suspect that’s because I noted the problem with the C64/C128 cartridges he sells.

  6. I just left a comment about the problematic cart port connector on the ‘MEGA65 January 2021 update’ YouTube video and it got DELETED!!

    Very responsible people…

    1. As far I know Gideon is using other Edge connectors now, so with newer boards the problem doesn’t exists anymore.

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