gwdoiron
Posts: 7
Joined: 06 Apr 2019, 14:50

SSS3 causes Turbografx system to become unstable.

06 Apr 2019, 15:32

System: NEC Turbografx-16 (HES-TGX-01)
Power supply: Manufacturer's OEM (HES-ACA-01)
SD Card / Cable: Purchased from Stoneagegamer.com at the same time as the SSS3. (Purchase date 4/1/2019)
Settings: "Per game backup RAM" and "Enable Arcade Card" checked, all others unchecked.
FW Version: 01.02 R05, FPGA C498
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The symptoms:
Playing any game, Hucard or CD, from the SSD3 will eventually cause a crash of the Turbografx. If the game is playing CD audio, the SSS3 continues to play the audio track even though the game has frozen (which may or may not also have screen corruption). Seems to always happen within 10 minutes.
I sold most of my games to get the SSD3 so I only actually have the Keith Courage cart to test. If I boot up the Hucard (with the SSS3 still attached), the system runs for at least an hour with no issues.
Last night, if I booted Keith Courage from the SSD3, it will crash after a few minutes. This morning, it seems to be working OK. Ys4 , however is still showing graphical corruption.
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Other issues:
The SSS3 case does not appear to be correct for the American Turbografx-16 console. It was impossible to install as shipped. The SSSD3 pin connector does not line up with the pins on the TG16, and the SSS3 connector needs to be raised up by at least 0.100" to get onto the expansion port pins. (This unit had a Turbobooster connected to it for almost 30 years, which just came off when I received the SSSD3 yesterday. None of the pins looked bent in any way, shape, or form, which I inspected before attempting installation.)
To get around this, I removed the unit from its shell, installed the board in the TG16, and put the shell back on, tightening the two rear screws but only loosely turning in the front two screws. I will need to order some #4 washers and put them between the bottom case and the PCB, so that the screws can be properly tightened.
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My proposed plan of attack for system instability:
1. Recap the Turbografx-16. (It's almost 30 years old, after all - parts have been ordered.)
2. If the recap doesn't fix the problem, instrument the incoming power from the power supply, and the 5V rail inside the Turbografx at the CPU. (I have a Lecroy HDO4032 at home.) The LM7805 used on the Turbografx has a 2V dropout and ~150mV worst case regulation. The oscilloscope should be able to capture minimum voltages. Replace power supply filter capacitor if the incoming power drops below 7.25V, replace 7805 if regulation is out of whack.
3. If everything seems fine on the voltage rails, I'll probably have to send it in for service.

Mobiusstriptech
Posts: 175
Joined: 13 Apr 2018, 15:41

Re: SSS3 causes Turbografx system to become unstable.

06 Apr 2019, 20:06

Based on the issue you are describing it sounds like the SD card is at fault here. I don't know what brand stoneagegamer is selling but I have seen similar issues when formatted as exFAT and/or on cards that basically aren't a SanDisk Ultra.

gwdoiron
Posts: 7
Joined: 06 Apr 2019, 14:50

Re: SSS3 causes Turbografx system to become unstable.

07 Apr 2019, 03:03

The SSS3 successfully reads the Hucard images and boots the machine, so I doubt that the SDcard is responsible for this, as I doubt that SDCard access is ongoing after the machine boots, and Keith Courage doesn't save to backup RAM. FWIW I was sent a Class 10 Kingston SDCard.
More notes: Attached a lab power supply to the Turbografx and fed the machine 7V, no boot. Boot but extremely flaky @ 7.5V. Boot and actual Hucard stable @ 8.1V. Fed 8.5V, but still issues with crashing using the SSS3. Machine is drawing ~400mA. Cleaned up PSU power connector with electrical contact cleaner, no change.

Mobiusstriptech
Posts: 175
Joined: 13 Apr 2018, 15:41

Re: SSS3 causes Turbografx system to become unstable.

07 Apr 2019, 14:32

The SD card is still accessed after booting and the issues you describe are exactly what have been seen with SD card issues. The fact that you don't see the same issues with an original HuCard should be enough to make that evident to you.

gwdoiron
Posts: 7
Joined: 06 Apr 2019, 14:50

Re: SSS3 causes Turbografx system to become unstable.

07 Apr 2019, 20:40

Actually, what is evident is that the unit is unstable when the TG16 onboard chips access the SSS3 (through the TG16 expansion bus). You can't draw any other definitive conclusions from the information given.

I am not the SSS3 hardware developer, but there is no way in hell that the SSS3 is designed to pass simulated cartridge ROM reads through to the SD card via SD commands, then pass the data back to the TG16. You will never be able to respond in time, you can't predict what address is needed in advance. The unit can only read the entire image from the SD card into the FPGA-accessible onboard RAM, and then use the FPGA to map that RAM into the TG16 memory map as ROM (at this point the only SD access is due to whatever housekeeping the MCU is doing for backup RAM).

1. Loading the game: SD card -> Micro controller -> Fpga -> FPGA RAM
2. Turbografx access: D8 bus on expansion connector -> Fpga -> FPGA RAM

The 2nd line item is causing instability. Therefore, I don't expect it to make a difference, but I went to Walmart and picked up a Sandisk Ultra Plus. I'll let you know how it impacts the setup when I'm done writing out the image and have tested it for a bit, if it helps, GREAT, I'll drop Stoneagegamer a note that he should probably switch up SD card brands, if not, you'll learn that the SD card isn't necessarily the only thing that can cause system instability.

gwdoiron
Posts: 7
Joined: 06 Apr 2019, 14:50

Re: SSS3 causes Turbografx system to become unstable.

07 Apr 2019, 23:39

I've tested the new Sandisk Ultra, as well as a generic no-name 1GB microSD card I had lying around, and have come to the conclusion that it doesn't make a difference which SD card I use. The Sandisk initially seemed to work longer before having image corruption or crashes, but as time went by, it eventually became flaky as soon as a game was booted as well.

Keith Courage seems to run through the demo loop without problems most of the time. I did have one occurrence of screen corruption on the title screen using the SanDisk card. I'm thinking that the game probably isn't pushing the TG16 hardware all that hard.

At this point, I'm waiting on the cap kit. Several of the filter and decoupling capacitors on the power rail are replaced by the kit.

Mobiusstriptech
Posts: 175
Joined: 13 Apr 2018, 15:41

Re: SSS3 causes Turbografx system to become unstable.

08 Apr 2019, 01:41

Well obviously you know more about all of this than anyone else. So have fun.


gwdoiron
Posts: 7
Joined: 06 Apr 2019, 14:50

Re: SSS3 causes Turbografx system to become unstable.

13 Apr 2019, 06:07

Recapping the TG-16 does not fix the problems, although graphical corruptions *seem* to occur less often now.

gwdoiron
Posts: 7
Joined: 06 Apr 2019, 14:50

Re: SSS3 causes Turbografx system to become unstable.

08 May 2019, 12:40

I went ahead and returned the SSS3 to Stoneagegamer.com, as I had no access to another Turbografx-16 to test the unit with.
They were unable to find a problem with the unit and shipped me a new one.
My TG16 continued to show the corruption/crashes even with the new unit.
I checked ripple on several bypass capacitors, worst case measurement was 47mV (on a 5V rail).
When I received the new unit, I noticed it took around 15 minutes for the graphical corruption to appear.
I opened up the TG16, removed the lower heatshield to expose the IC's and spent about an hour probing with a heat gun and a can of compressed air.
I was able to mimic the problem by heating up the Huc6280 microprocessor, and the problem went away when I cooled it down with the compressed air.
I ordered some Huc6280's from Hong Kong Game Doctor Games (gamedoctorhk.com). They arrived last night, and I replaced the Huc6280 on my TG16.
The unit has now run 6 hours without any graphical corruption or crashing, and seems to be fixed.

The unit is running with the original Kingston SD card that Stoneagegamer.com shipped with it. The problem was with my TG16 unit, not the SSS3 or SD card.

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