The Sega Saturn and the dreaded PLL chip

[iVirtualZero]

After working on and modding multiple Sega Saturns. I came to the conclusion that the Sega Saturn mainly the Model 1 has a major fault that is not repairable and this fault is becoming more and more common as time goes on. And it’s a shame for a system with so many awesome games and mods available for it but no fix for this fault that plagues many Sega Saturns. And this is because of the fragile PLL Chip which is essentially a clock/oscillator chip. And when this fails you end up with the dreaded black screen or unstable video, but if your lucky it could be a bad psu, bad caps, failed bios mod, bad ribbon, trace, if not it’s the PLL chip. There are suggestions for trying to fix such a fault, such as replacing the caps or some of the chips, but ultimately it’s the PLL chip that is primarily at fault and there is no replacement for it. Even if you try to get it out of another motherboard you easily risk heat damaging the chip. When buying a Sega Saturn to fix, stay away from most of these black screen Sega Saturns or any with video issues and modders, don’t solder to or near the PLL chip as they are heat sensitive.

I would love to see someone come up with a modern replacement for this chip that is reliable and not heat sensitive, there are already 50/60hz DFO (Dual Frequency Oscillator) mods for the Sega Saturn but i’m not sure as to if they bypass the PLL chip altogether or rely on it. I have yet to find out and will see if that mod bypasses it. Anyone that is a fan of the Sega Saturn and has such skills of reverse engineering this chip and coming out with a replacement. It would be a dream to see such a mod become a reality. I wouldn’t even mind it being an open source project, utilising already available mods like the DFO mod. This will save a whole bunch of those black screen Sega Saturns and i have 5 with such faults.

There are also other people encountering such faults https://segasaturngroup.proboards.com/thread/11442/broken-saturn-after-60hz-mod

https://segasaturngroup.proboards.com/thread/11916/extreme-video-fluctuation-crashing-reading

VA0 to VA5 and the VA9 Pal version uses PLL chip (Hitachi HD49422)

And it looks like somebody has decapped this chip: https://www.icreversing.com/chips/315-5746

VA6 to VA9 Models 2’s use a later PLL chip (CY2292SC) which seems to be much more reliable, but black screen problems can occur even on a model 2 though much less common than the model 1’s. And good news with the model 2, you can still buy replacement PLL chips though i’m not sure if it needs to be reprogrammed or not.

Repost: https://videogameperfection.com/forums/topic/the-sega-saturn-and-the-dreaded-pll-chip/

https://segasaturngroup.proboards.com/thread/12278/replace-pll-chip-sega-saturn

• This topic was modified 1 year ago by iVirtualZero.

[BuckoA51]

Indeed I’ve definitely seen a few Saturns with that fault. A clone/replacement for that chip would be great, and something we would definitely stock.

[iVirtualZero]

Yes it would be a repair dream come true. It mainly affects model 1’s and i would love to see a modern replacement for both the model 1 and the model 2. Perhaps a more custom DFO mod.

[BuckoA51]

Zyrobs over there on the SSUK forums is very knowledgeable, unfortunately like most of us who used to post there regularly he’s mostly given up on that forum. I’ll keep checking and see if I can obtain more details about the PLL in the later model Saturn and see if there’s any equivalent on the market at the moment.

If we do manage to get to that point, do you have a PLL damaged Saturn we could maybe purchase from you to experiment on?

[BuckoA51]

@ivirtualzero would you be willing to sell us one of your broken Saturns to experiment on?

[iVirtualZero]

Yes that would be appreciated to reverse engineer it and come out with a way to clone this with a more reliable chip that isn’t heat sensitive. I have two units VA0’s that i have recapped and even with that i’m still getting a black screen. The other one i remember i damaged a bunch of traces on the bios fixing it and recapping it got it working for a bit until i randomly lost video and got a black screen. The others all of the traces are intact but i think the excess heat may have damaged the PLL. And the rest i have yet to recap and find out. I also have yet to see if replacing the EMI Filters could fix some of these. I think if i try this one last fix on these two units and nothing happens, then i will be happy to sell to you as it’s pretty much guaranteed to be a bad PLL causing it to not boot.

[iVirtualZero]

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• This reply was modified 9 months, 2 weeks ago by iVirtualZero.
• This reply was modified 9 months, 2 weeks ago by iVirtualZero.

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