50Hz 60Hz Switch (Sega Saturn)
The Sega Saturn has various revisions so performing the mod depends on version.
As with most consoles to do a frequency mod the principle is to send a specific pin to ground or 5V.
Every revision of the console can be done/reverse engineered from the same point if needed.
The video mode is controlled by the VDP2 315-5690 (pin 79 Video Mode). This chip can have several revisions, but it is always pin 79:
- 315-5690 (VA0 CCI JAP, PAL cards)
- 315-5964 (VA6 SG JAP & VA7 PAL cards)
- 315-5744
- 315-5890-02 (PAL SD, VA9 PAL cards)
This pin also joins to the CXA1645M video encoder (pin 7 NPIN) or the BH7236AF (pin 7 NT / !PAL) depending on version, and to the 315-5746. We DO NOT want to change the CXA or 315-5746 pins.īģŋ
Sending just the VDP2 pin 79 to ground outputs 50Hz. Sending it to 5V outputs 60Hz.
Some revisions already have this pin wired to a blank switch pad at the rear of the console, and others have a test point and jumpers.
This method works on every revision Saturn.
Quite simply, lift pin 79 of the VDP2 (315-5690 / 315-5964 / 315-5744 / 315-5890-02) and send it to Ground for 50Hz or 5V for 60Hz.
I lift pin 79, attach it to the middle of a switch, and send the other sides of the switch to a ground and 5V pad.
Ground can be tapped off from the ground trace in the battery door and linked to one side of the switch.
Here you can see the 5V is on the left (going to the other side of the board), pin 79 is going to the middle pin, and ground is on the right.
Switching to the right (to ground) enables 50Hz. Switching to the left (5V) enables 60Hz.
5V can be found usually just on the other side of the board on a capacitor (just test continuity to the 5V power input pin).
On some versions it appears Sega intended to even have a switch in the battery compartment door at the rear, specifically for frequency switching.
If you have a version with the empty switch pads all you need to do is add back a switch that connects the middle and right pad together for 60Hz and left open for 50Hz.
Ground is 50Hz, and 5V is 60Hz.
I solder the cage of the switch to the ground plane by exposing some of it. This anchors the switch solid to the PCB.
You can also close the back door without issue. Notice I trim the black plastic surround inside by removing the bar that would otherwise run past the switch.
Sliding the switch to the right outputs 60Hz, sliding it to the left outputs 50Hz.
Some revisions have JP1 and JP2 which can be used.
Measure in continuity if JP1/2 shared pad (FREQ) connects to the CXA pin 7.
If it does, DO NOT use this method.
JP1 goes to 5V on one side. and the other side joins to the JP2.
JP2 goes to ground one side, and the other side joins to JP1.
When 5V (so JP1 bridged and not JP2) it will be in 60Hz (US/JAP).
When Ground (so JP2 bridged, not JP1) as shown, it will be 50Hz (UK/EU).
From understanding this and looking at it, you can deduce that the shared pad where both JP1 and JP2 meet is the Video Mode pad that goes to the VDP2 and the CXA1645M video encoder (pin 7 NPIN).
Remove both resistors from JP1 and JP2 if present.
Now install a 10k or similar resistor on JP1 to pull the Video Mode pad to 5V.
Finally, solder a switch with one side to ground, and the middle common pin of the switch to the Video Mode pad (the one where JP1 and JP2 join together, or pin 79 of VDP2, or pin 7 of CXA1645M).
Switching the switch to the side with 5V outputs 60Hz. Setting it to the free/unconnected side lets it get pulled to ground by the 10k resistor, outputting 50Hz.
A quick note on the zones. Independent of the consoles frequency, we can set the zone (language).
This is done through a set of resistor jumpers on JP6/8/10/12 as shown below.
For example regions the following jumpers are installed:
Region | Jumpers |
NTSC-1: Japanese Saturn configuration. | JP1, JP6, JP9, JP11 and JP13 |
NTSC-4: American Saturn configuration. | JP1, JP7, JP9, JP10 and JP13 |
PAL-C: European Saturn configuration. | JP2, JP7, JP9, JP10 and JP12 |
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