Extreme video fluctuation/crashing when reading discs

[tiramisu]

Hi there everyone,

Hopefully as a first post this won't be up there with the worst of them.

I have a Model 2 Saturn (board is labelled "PC BD SATURN MAIN VA9"), its had its laser replaced and the VDP set to run at 60Hz, and ever since I first owned it I noticed there was slight fluctuation in the video signal whenever the disc is being seeked (most notably as the laser travels along the rails). I put this down to power issues and only now got around to recapping it as that's all I could think to do. Unfortunately, that only made things worse.

After recapping the console will boot fine without a disc inserted however as soon as it goes to read one the video fluctuations are even more severe and the console very soon after blacks out or crashes and does not recover without a full power cycle with the disc removed. It's beyond me how replacing the twenty-something year old capacitors can do such a thing but I'm positive it can't be anything else.

A while back I made a BOM for all the electrolytic caps on the mainboard, but at this point I'm not sure what good replacing those as well will do. I'd be happy to share it here in case anyone wants it as I couldn't find it in the usual places like Console5.

Does this sound like an issue anyone else around here has experienced? I'm at a loss myself and don't know how to proceed.

[zyrobs]

When I had the same issue, a recapping helped, but you still had to leave the console on for a while for it to "warm up". After which it worked fine for a longer time.

Another user mentioned that replacing the main crystal fixed the issue permanently. This would make sense since this is a clock issue, although I didn't knew that crystals can break down like that over time.

[tiramisu]

Oct 2, 2021 5:07:55 GMT zyrobs said:

When I had the same issue, a recapping helped, but you still had to leave the console on for a while for it to "warm up". After which it worked fine for a longer time.

Another user mentioned that replacing the main crystal fixed the issue permanently. This would make sense since this is a clock issue, although I didn't knew that crystals can break down like that over time.

Would that be X1 on the board? replacing that sounds like it could help

[zyrobs]

X2, but yeah. It's a 17.734475 MHz one in PAL machines. Should be easily available.

[griffin22]

Hi all,

I have a very similar issue with my VA9 board. Extreme fluctuations when trying to load and then freezing, a power cycle with the drive door opens allows it to boot again but closing the drive door gives the same result but sometimes also black screening. To try and remedy it I have recapped the power board, CD drive board, main board fully and replaced the X2 crystal, although I couldn't find any of the correct form factor so I used one that fits in X1 and just removed X2. I am waiting on some of the correct crystals for X2 as that X1 replacement was just to test, but it was unsuccessful. I am at a bit of a loss with this one, might it be one of the other crystals on the board causing the issue? And does anyone know what frequency they are so I can try replacing them?

Cheers

[zyrobs]

The rest of the crystals shouldn't cause an issue, the problem is interference with the signal generated by X1. Unfortunately we don't know much more about the problem, someone with a scope would need to analyse the nature of the error, but I've got a feeling that it's simply the PLL chip dying.

[griffin22]

Before I swapped the crystal I tried it with my fenrir and it loaded some games perfectly and some worked but had a high pitched static noise mixed in with the audio. I only changed the crystal this morning though so I need to repeat the test again.

[griffin22]

Hi all,

Quick update on my issue. I have changed all the caps on the board, the crystal and the two 74VHC04s that take the output from the pll (ic23 and ic24 if I remember correctly). Unfortunately it is still behaving exactly the same as before. Boots fine, plays some games on fenrir OK but most not great, and won't boot from the CD drive at all. Excessive wobbling on drive spin up and then when it goes full speed she crashes and can't be recovered without a power cycle with the CD door open. All things seem to he pointing towards the PLL gone bad, so I was wondering if there are any replacement PLL chips available that are pin compatible at all? I have an old VA9 board I was considering swapping the PLL from but realised that the VA9 uses a different PLL so that plan is out. Without replacing the PLL I fear this Saturn may become a pure parts unit, which is a shame as its in really nice condition.

[zyrobs]

Oct 22, 2021 10:41:23 GMT griffin22 said:

I have an old VA9 board I was considering swapping the PLL from but realised that the VA9 uses a different PLL so that plan is out.

I'm curious as to how that is possible, since to my knowledge all VA0-5 variants, VA9, and VA7 PAL use the same PLL chip: Hitachi HD49422 315-5746.
Unfortunately the chip is extremely fragile, you'll most likely destroy it if you try moving it from one console to the other. There's no known source for good chips either.

The only other idea I have is populating the unused capacitor slots (CE 101 to 113), but for that we need someone with a scope to measure the noise on the rail that we have to filter out.

[griffin22]

Sorry, that's my bad typing, I meant to say I have an old VA0 board that I was considering swapping with.

It's a shame there aren't any sources of these chips as I have a couple of consoles with very similar problems, but I haven't yet tried replacing the caps and crystal on any of the others yet. They are all VA9 boards, but I'm not sure if that's because the VA9 is prone to this or if its just because they were so common in the PAL region.

Hopefully someone with a scope will be able to figure out capacitor values that would be recommended.

[griffin22]

I have just checked both the boards (should have really done that first rather than relying on information from segaretro as I had them both in front of me, foolish boy I am) and you are indeed correct that the chips are identical on the VA0 and VA9, so I may give it a bit of a go over the weekend. It certainly doesn't look like an easy job though, but at this point I don't have much to lose with trying.

Thanks again for all your help with this!

[zyrobs]

I do not recommend trying to switch the PLL, they are very fragile chips and there's a good chance the heat from the soldering work will destroy them.

Instead try putting spare caps of increasing capacitance values on the board for the positions marked CE 106 to CE 111. If there's any noise on the 5V rail, then putting caps there should help things, but without a scope we don't know if there's any noise, or what's the frequency of the noise (and therefore what caps would best filter them). So you have to try doing a crapshoot to see if it helps.

Oct 22, 2021 15:39:02 GMT griffin22 said:

They are all VA9 boards, but I'm not sure if that's because the VA9 is prone to this or if its just because they were so common in the PAL region.

VA9 was almost exclusive to PAL consoles. In NTSC ones it only saw limited release in Hi-Saturns and V-Saturns. It was also a "universal" board where you could switch pal/ntsc setup with just a few discrete components (a crystal and some jumpers). And yeah, those can have this issue too, but I don't know how severe, the only NTSC VA9 I had worked mostly fine.

I recall people mentioning that other model 2 boards had similar problems, but as NTSC boards used several different board types, and because import costs are ridiculously high, I can't really test them. The closest in board layout would be the VA8 OCU, which uses nearly all the same parts except for substituting the main SDRAM with SGRAM. But it uses a different PLL - they started using a different chip from VA6+, VA9 was the only one still using the old part, probably because it is compatible with both PAL and NTSC modles. And no, the new PLL isn't a drop-in replacement, since it doesn't handle PAL clocks and uses a different form factor.

[griffin22]

Hey Zyrobs, thanks for the information. Unfortunately I didn't see your post until I had already removed the donor PLL, so I just rolled with the swap thinking I didn't have much to lose. The donor is off a scrap board I got a while ago and have already used the VDP2 to fix my model 1.

Its a bit of an interesting result though. After the swap it was initially it was behaving very similar, crashing on the menu screen when trying to read the disc, but when I tried to boot with the lid closed it actually managed it for the first time! I played it for a minute of two and then opened the lid to try and boot from the menu again, and again it crashed. This went on for about 5 or 6 goes and then after playing a game for 2 or 3 minutes I was able to go back to the system menu, and reload the game with out issue. Tested it 3 or 4 times and it was just happy loading from the menu now. So she seems to be on her way to recovery finally.

I need to replace a few of the caps around the PLL as they took a bit of heat during the process (it's a bit crowded around there) so better to swap and be safe, I'll also look at throwing some caps on the 5V rail as you suggest to see if that helps reduce the wobble further, it's a lot better than it was but is still slightly present.

Thanks for all the help, it's all invaluable!

[zyrobs]

That's the thing that makes this problem difficult to diagnose, once you played with the console for some minutes or hours, the problem starts to "fade" away, it'll start crashing less often, then none at all. I have a VA9 unit that when I tested last week or so, it crashed nonstop. When I tested it earlier today, it crashed only once and played fine after that.

I don't know how to describe that other than that it needs to "warm up". The heat from the soldering also probably helped with that.

[griffin22]

It's always fun trying to pin down unreliable faults! I'll leave it to cool over night and give it another go tomorrow. It was a nice feeling to see I hadn't screwed it up doing the swap though. And then also seeing it boot up into the rather beautiful panzer dragoon first level music. It certainly brought a smile to my face.

Thanks again for all the help with this.