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Jupiter Ace ROM select [ROMSL] Modification

The ROM select [ROMSL] signal is missing from the edge connector of the standard 3K Jupiter Ace. On the Ace4000 its been added to the first unused edge connector pad, next to the key on the solder side of the pcb.

The ROMSL signal can be connected directly to the 5+ volts to disable the Ace's Forth ROMs this will allow other interfaces and devices to take control with their own on board ROMs, such as the AMI project.
In The following modification the ROMSL signal is added to an unused edge connector pad next to the key on the solder side of the Ace's pcb, the same as the Ace4000. Warning! Do NOT carry out this modification unless you are 100% sure you have studied the images and feel confident at doing the work, otherwise you may damage your Ace. To open your Ace's case see the Tear Down page.
The modification involves cutting two pcb tracks and soldering in two 1K resistors and IN4148 diodes. Study the image below of this unpopulated Ace pcb which shows the tracks to be cut, also the edge connector pad that will be used for the signal.
Parts needed are two 1K resistors and two IN4148 diodes
Parts needed are two 1K resistors and two IN4148 diodes.

Pad and cut locations
The solder side (underside) of the Aces pcb.

pcb cut tracks
Here you can see the pcb cut tracks.

The diodes are soldered in place first

The diodes are soldered in place first. When soldering the diode to the edge connector pad keep the solder join as close to the edge of the pad as you can. So when an interface is pushed in place it will not damage the connector. Do one final check to make sure the diodes are the correct way around.


Next the resistors are added

Next the resistors are added, take extra care when soldering them to the pcb track. Check for solder blob shorts between the tracks. You may have to scrap some of the solder resist away from the track before you can solder the resistors in place. Your ROMSL signal is now complete
Another Ace with the same modification made

Another Ace with the same modification made.

Another Ace with the same modification made

Another Ace with the same modification made