Corrupted TG-CD memory?

[kid_rondeau]

Has anyone ever had a situation like this?

I started a new Dynastic Hero quest, as I do every year around this time. But for some reason, when I try to make the transition from the first calypso/water area to the first town (the one that's infested with walking mushrooms), the screen goes black, the CD spins, loads, and then does nothing. I've waited five minutes, ten minutes...it makes no difference.

Being a reasonably scientific and logical person, as well as a collector of TG and TG-CD systems, I had the freedom to play around with various system components until I found the guilty party...

TG16: OK
TG-CD: OK
Super System Card 3.0: OK
TG-CD Dock: NG

Of course, the game itself could have been part of the problem, but I only have one copy of DH.

So....the dock was the weak link! I asked myself what about the dock was special in any way, and that's kind of where my already tenuous knowledge of data storage becomes even more deficient. The save files are stored somewhere in the TG-CD dock itself, right? Anyone know where? Is it possible for this to become corrupted? I tried formatting my system several times, but this didn't solve the problem.

I guess it wouldn't be that hard to swap out the mainboard from my "good" dock (which only has composite out) and put it into my wonky dock (which I've modded with S-Video). Has anyone ever tried this?

Any thoughts, input or suggestions are welcome!

[kid_rondeau]

UPDATE:
It isn't just DH that causes this problem...it's any CD game where there's a save option. As soon as the game progresses to a point where you'd normally be able to save, all loading stops. Very strange.

[SignOfZeta]

That's a new one. I'd assume this is a hardware problem that is going to have you either repairing the dock or getting a used one.

The only thing I could think of would be to reformat the save memory.

[BlueBMW]

I've got a spare loose TGCD dock if you need it.

[Twood1130]

What does the Cd Dock use for saving? Is it a battery, or an NVRAM chip?

[SignOfZeta]

Its RAM kept alive by a capacitor.

[kid_rondeau]

Oh! Do we know which cap? Would it be obvious in any way? Large, or otherwise?

[nikdog]

Here it is on the PC-Engine IFU. I would assume it to be similar in the TG dock.

[kid_rondeau]

hmm...no picture/link supplied.

[nikdog]

_{pc_engine/ifu_30_06.jpg
pc_engine/ifu_30_05.jpg}

It's having trouble displaying on the forums for some reason. It works occasionally.

[kid_rondeau]

Ok, the links are there...but they just go to some Japanese Yahoo! error page... what does it say?

[NecroPhile]

"Sorry, this page is currently unavailable. Please try again later. If you have any questions, after refering to the help, please contact us."

If you cut and paste the text into a new tab, they'll work.

[kid_rondeau]

Whoa! Awesome! Thanks guys!

[Charlie]

Standard supercap.
They dry out the same as any other cap.

You can use a VOM to check the voltages before system usage, immediately after system is turned on, after the system has run a few hours, and finally after the system has been off a few hours.  The changes in voltage will tell you a lot about the condition of the cap.

You can also connect three 1.5V cells in series, and temporarily connect them to the capacitor (observe polarity!).  Then try a Save, turn off the system for a few hours, and see if the saved data is still there.  If the batteries allow a long-term Save with the system off, then you know it's either the cap or it's power circuitry.

 You should also realize that, even in normal operation, a supercap that has not been powered in a long time may take hours, or even days, to re-form and hold a charge once you apply power.  Have you actually left your system powered on for, say, a full day (overnight?) for the capacitor to charge, then left it off for several hours, before concluding the Save isn't working?

Charlie

[kid_rondeau]

Thanks for the info Charlie!

It's tough to explain my problem with the memory. It's not like it can't save files...it can, so long as it's a chip game. The problem is only with CD games that allow you to save/load files at will (like Ys, or Dynastic Hero). Those games start OK, but once you get to a point where you'd normally be able to save the first time, the screen will not load at all.

Maybe that supercap's got something to do with it, and maybe it doesn't. All the same, I think I'll take a look inside my malfunctioning TG-CD for anything obvious in that neighborhood. If not, I might just swap it out for practice. It couldn't make things any worse!

[nikdog]

It's tough to explain my problem with the memory. It's not like it can't save files...it can, so long as it's a chip game. The problem is only with CD games that allow you to save/load files at will (like Ys, or Dynastic Hero). Those games start OK, but once you get to a point where you'd normally be able to save the first time, the screen will not load at all.

So wait... You can use Turbochip save/load no problem?

[kid_rondeau]

That's correct. I can save on chip games that allow you to save your progress (like Neutopia or Dragon's Curse), as well as chip games that automatically save your high score (like Soldier Blade). I can also play CD games with no save feature (like LoT). The problem, as I've experienced it, only comes with "save-at-will" CD games.

FWIW, on any CD game I play on that dock, there tend to be very minor graphical glitches. For example, during the armor selection screen on LoT, the flames on the torches in the background are all garbage-y. In all other ways the game plays fine though.

[nat]

That sounds suspiciously like a System Card that is not seated properly, has dirty contacts, or is beginning to go bad (not that I've ever seen the latter). I have problems like this with Sapphire if the Arcade Card isn't seated perfectly.

[nikdog]

Do you loose all your saves after a full power cycle (dock power switch off)?
Do you know if the memory is full? I don't know if that would do anything weird but it is worth a check. (Vasteel 2 has a built in memory manager that will actually tell you how many blocks are free and being used, but it requires a SCD card.)

It seems to me that this is probably a problem with the TG16-CD interface.
Edit:Or this:

That sounds suspiciously like a System Card that is not seated properly, has dirty contacts, or is beginning to go bad (not that I've ever seen the latter). I have problems like this with Sapphire if the Arcade Card isn't seated perfectly.

[kid_rondeau]

Hey guys, to address your thoughts:
-I don't lose my save files with the system off. I actually just tested it now, and the save files I made on 11/30 are still there. I haven't used it since then.
-The memory's not full...I've formatted it several times.
-I don't think the SSC 3.0 is at fault; the save issues and graphical screw-ups still happen with the regular System Card 2.0 and the Arcade Card Pro.

Another thing I wanted to try is a CD game with automatic saving after each level (like Valis III). As I expected, the game loads OK, then all the cut scenes play, but the game locks up before the last cut scene that precedes the first playable level.

Hopefully when I finally have time to open the dock and poke around something obvious will pop out, but probably not. I'll start with replacing the supercap (which I would give only a 10-15% chance of fixing the problem) since it's a cheap and easy solution. But not until after the holidays...I'm swamped!

Thanks again for all your suggestions, thoughts and perspectives. I welcome them. If this is "a thing", then I'm probably not the only one who's had or will have this problem. It would be nice to have some data about it.

[nat]

Here's the deal: the BRAM has absolutely nothing (zip, zilch, ZERO) to do with in-game graphics. A bad BRAM supercap *might* cause the saving issues you're describing, but would definitely *not* cause graphical glitches you describe playing CD games.

Let's look at the facts: the save issue/game freeze issue only happens with CD games. The in-game graphical glitches only happen with CD games. The issues happen regardless of System Card used. Bottom line: the issues at hand only affect CD games.

I'd bet my next paycheck the 64K DRAM that the CD interface dock uses for a sort of "work RAM" is bad, or at the very least a nearby cap has leaked electrolytic goo onto its legs. This 64K DRAM is used by all CD games regardless of System Card and is NEVER used by cartridge-based games. It also has nothing to do with your save game BRAM, but it's quite possible the system might use this 64K space to "prepare" the save file for CD games before actually copying it over to the BRAM.

IMO, and you can take this as you will, you are wasting your time chasing ghosts looking for something in the BRAM circuit.

[kid_rondeau]

Nat, thanks again for your input.
I don't know what the B in BRAM means...nor can I find any reference to it in a 20-second Google/Wikipedia search...but as I've said before I know just a little more than diddly squat about how anything saves a file anywhere.

I also wanted to clarify that I never once, even for a second, thought that bad save memory/RAM was causing the graphical glitches. In fact, the glitching was very much a secondary concern that I only noted because it was seen concurrently with my save issues.

When I eventually do open the case, I will look for an obvious visual defect (a leaking cap, as you've suggested) in that neighborhood. Do you know where this DRAM might be? Could it be in Nikdog's pictures?

As always, further comments/advice are welcome, and I'll keep you all posted on my findings.

[SignOfZeta]

I also wanted to clarify that I never once, even for a second, thought that bad save memory/RAM was causing the graphical glitches. In fact, the glitching was very much a secondary concern that I only noted because it was seen concurrently with my save issues.

Yes, but one of the main tools in any diagnosis of anything is to find all the flaws and see if anything could tie them together. In this case...graphical glitches in only CD games + saving glitches in CD-only games...what do these things have in common? The 64K of RAM in the CD base (or something very close to it).

Its not a common problem, but it is the most likely at this point.

[NecroPhile]

I don't know what the B in BRAM means

B is for Block.

[MottZilla]

Block RAM? I would think the PC Engine uses Parallel RAM which is either going to be SRAM (Static RAM) or DRAM (which requires support circuitry to refresh its contents). Block type access would be way too slow and wouldn't work for program execution on the PCE. Sometimes people say BRAM as in Backup RAM. Which is similar to how many people think of emulators and SRAM means Save RAM.

Either way I'd think the first step would be to open it up and visually inspect the board and components for damage or shorts. If nothing is obvious then maybe you need to look around for the RAM chip or chips for closer examination. Also is it possible that the Expansion connector is dirty or has bent or bad pins? Since the Super System Card connects from the HuCard port and the RAM in the CD unit is connected by the expansion port maybe that has something to do with it? Worth looking at I think.

[nat]

In this application, BRAM is meant indicate Backup RAM to differentiate it from the system's work RAM (DRAM) and VRAM (video RAM).