Saturn VA0 PAL control port issues

Hi there.

I have a Saturn Model 1 VA0 PAL console here with an interesting problem quite similar to the thread created by Eidolon_NG.

The control ports presumed to have an issue with power output to the pins.
Capacitors for CE47,CE48 have been replaced.

Here is a summary of a few tests using 3 devices in a single port configuration.

Standard digital only controller third party
Both ports -ok
Test -ok

Official 3D Knights controller black
both ports -bad, negative function, not detected
X\O mode -bad, negative function, not detected
Action replay 4Mplus -menu infinite loop observed
Test bad

Brook Wingman SD adapter.
Both ports -Status LED varied intensity (port#1/#2),
Button on adapter needed to be held to see very dim LED
Device not initialized, negative function, not detected
Test bad

External power applied to the adapter via usb/pc port
Device init -ok
X\O mode -ok
Slow and intrusive analog stick drift (up direction) observed
Action replay 4Mplus -menu infinite loop observed
Certain games 'burning rangers' exhibit random inputs, unplayable
Test bad

In all instances where the AR4M+ menu was sent into a loop, disconnecting all controllers, and reconnecting the digital only controller to port #1 was the only means to end the loop and stop the madness of potential random inputs.

I did test the console in 2 port configuration, very mixed results with similar conclusion.

I highly suspect the issue could be the row of resistors? connected to the pins for each port.
Any insights alternatives and specifications of these little dark magic boxes would be much appreciated.

The only advice I've been given so far is a replacement board, which would mean trashing a 99% working VA0 board entirely.

Thanks for any assistance guys
have a good one
Alright I've scanned the board with a scope to get a more accurate picture of the issue.

There is a row of emi filters near both control ports which appear to be the main cause for this problem.

Does anyone know of a source for these ?
"Taiyo stb101kb" is the part name.

Taiyo appears to have merged with another company called Yuden during my search for the parts.
Would these parts or an alternative still be available?

Thanks again.


Extra Hard Mid Boss
You can probably just bypass them. The filter's job is to remove high-frequency noise picked up by the controller cable, but it's one of those components that are often strewn around to make sure you pass EMC certification rather than to fix an actual diagnosed problem. If you really want to replace them, something like this is probably pretty close, but no promises.

(Some filters integrate a TVS component, to protect against static electricity zaps, but I don't believe that's the case here.)
Bypassing them has been a consideration for sure.

Due to the strange problem i have with analog controllers or other devices like the wingman sd adapter,

I can only presume that the SMPC chip is simply not 'seeing' a signal it expects (due to fluctuations) for peripherals like analog controllers and such, and so doesn't initialize power and control.

Or would a noisy signal be a non issue for the chips detection and power up process?

The slight analog stick drift noted with an externally powered wingman sd smells like extraneous noise causing the drift, right?

As I confirm that the system is 99% fine, digital controller and games run fine for hours on end with no problems, I presume it would be safe to rule out the SMPC chip for fault, as i would expect far more problems if the chip was faulty.

Thanks for the information so far, this seems to be a very rare problem.

The only alternative advice i've been given is to trash the board and get a 'new' one.... not really keen on that idea though, not yet.


Extra Hard Mid Boss
Did you measure the 5V line at the controller side, to see if it's drooping or glitching? The 6-button pad probably consumes the least power of all controllers, and an unstable power supply will affect A/D-converters. Based on your description, the next most likely culprit would be pin 6 (TL), which IIRC isn't used by the 6-button pad protocol. If any of the other signal lines were glitching, it should affect the 6-button pad as well.

Also, if you haven't, first check for cracked or cold solder joints. Simply reflowing them may help.
I probed both ports on via TP34 through 25 directly, readings were similar at the controllers pcb pin also.

With digital controller, Voltage was around +1v with some variance.
And dropped with time after disconnection, as expected.

With the wingman sd, Voltage gradually increased to a level which never reached +5v, showed more obvious fluctuations of drooping and very short spikes.

Both ports have slight but noted differences in readout, depending on what/if anything is connected to the other port at the time.

With external power, the 3D function works but has a noticeable drift left+up
very easily seen with slavedriver games.

The system also shows an interference pattern on the screen if the adapter is externally powered, something not seen when testing the adapter with Dreamcast.

I should note that during very early tests, port #2 was able to power up the adapter and the knights pad, not very useful for 1 player games.

Port #1 was only sending random inputs @50hz mode. and had negative function @60hz. other than looping AR4M+ menu that is.

After switching digital to port #2 and knights/adapter to port #1, Port #2 went bad somehow and was no longer able to power up the adapter/3D pad unless ext power was used. At this point I uhh WHAT!? ...

As you can tell, this is a bit strange yea?

Cheers for the assist.
Does anyone know of a source for these ?
"Taiyo stb101kb" is the part name.

Look for EMI101T-RC. It is a bit too thick (2.8mm instead of 2.54mm) but for the controller ports this isn't an issue.

For the video and comms port filters, you have to get creative to get them to fit (bend them to the sides like a flower petal).

Murata had an ideal part but it has been removed from the market for far too long.
Thanks for the information guys, much appreciated.
I'll give these alternatives a shot and let you know how the story ends.
Interesting question!

Due to my limited knowledge of how the chip behaves,
I wouldn't expect the readouts to be any different, as the chip itself may have no reason to provide any more than the controller needs.

The question then becomes, what does it think it sees here? and what is it attempting to provide?

Without a good scope, I can only speculate it defaults do digital mode if the pin is too noisy or lacks attenuation.

However, with only the wingman sd connected port #1, the voltage gradually increases slowly to an unstable 3.x v the device never completes init/post but the AR4M+ menu loops just fine over and over, unless you hold a button.. So y'know, that's.....something?

It's almost as though the filters are acting like resistors, confusing the chip and weakening the line if higher voltages are pushed. This could explain why those 2 capacitors failed simultaneously after being stressed out by a modern power hungry device.

I've got the alternative filters on the way, and an alternative VA0 board in sight.
This can not possibly fail twice in a row....again :)


Extra Hard Mid Boss
Based on what you describe, it sounds like the controller port is unable to supply enough current, which is causing the voltage to drop. Since the 6-button pad is an extremely simple device, it may just get enough power to function, but anything that requires more either becomes unstable or stops working at all. The Wingman SD behavior is probably caused by capacitors in the device, which can draw fairly large currents until charged.

That's why I asked about the voltages at both terminals of the filter. If the input is 5V and output 1V, it's a pretty strong indicator of what's going on.
I have the parts now, I'm goin' in! I'll let you know the results.

As for the voltage readings, it's likely the drop was potentially caused by the faulty part still in circuit.

And due to the way some of the pins are wired, isolating all of those in series would be required to get a more accurate reading there presumably.
Ok well, i've replaced the set for port #2 only at this time.

Good news is, no smoke and flames!
Status led's have more intensity than before.
digital pad still works ok.
Always fun to restore save and clock settings.

As always there's no news like bad news so.

I tested the pins for port #2 out of line at the via
results were nil as expected, not possible to connect a pad :)

After i replaced the filter set for port #2, the adapter status led have greater intensity,
still no init, not enough power. Voltage at the vcc via was higher, but still below 5.

Unless Sega has performed some dark sorcery which requires both ports at 100%, I'm at a loss with this one.

Amused by the results from port #2, I can't say I'm to exited to follow up and finish the other set for port #1.

Conclusion.. board is hexed ?