3D Controller problems with PAL Model 1 Saturn

Eidolon_NG

New Member
Hi,

after de-mothballing my PAL Saturn after about 15 years, I notice that some controllers do not really work well with it anymore.

Hardware info:
- Model MK-80200-50
- Mainboard: Seems to be a VA1? (PCB info: Made in Japan, 171-7069B Main, 837-11892-01:pAL)

The symptoms are (tested with controller port 1 and port 2 - same behaviour to be observed)
- one 3D controller (set to digital mode) does not work when it is already plugged in during power-up. When I re-plug it in after power-up, it starts to work (and then works fine)
- a second 3D controller (set to digital mode) does not work at all, neither when plugged in during power-up, nor when re-plugged in after power-up
- regular, non-3D controllers seem to work fine, both when plugged in during power-up

What I already did is
- clean the Saturn controller ports with Isopropyl alcohol and bend the controller port pins up a bit again so they have a firmer grip towards the controller plugs
- clean the 3D controller plugs with toothbrush and Isopropyl alcohol
- clean the 3D controller "plug-in plugs" with toothbrush and Isopropyl alcohol
- clean the flat cable between mainboard and controller port PCB with Isopropyl alcohol

My questions:
- Do I have a problem with one or both of my 3D controllers, my Saturn, or both?
- What can I test to evaluate further and pin-point the problem?
My lab-at-home is equipped with soldering station, multimeter, logic tester, so I can use all of these to hunt down the error in either device (3D controller or Saturn)

Thanks in advance - any help appreciated!
 

antime

Extra Hard Mid Boss
When the controller is plugged in when turning on the power, does the Saturn otherwise work fine (shows the start animation, boots the CD etc.)? If you swap the cable part of the controller, do both controllers behave the same? Have you opened the controllers and looked for any obvious faults? Do you get anything unexpected if you measure the resistance between each controller pin and Vcc, or each pin and ground?

If the "TL" pin is stuck high, it could cause a situation where regular 6-button pads work, but not any peripherals that used the 3-line handshake. Do you have a mouse, keyboard or multitap that you could test?
 

Eidolon_NG

New Member
When the controller is plugged in when turning on the power, does the Saturn otherwise work fine (shows the start animation, boots the CD etc.)?
Yes, the Saturn itself is still working fine, and I enjoy playing it with non-analog controllers. :)

If you swap the cable part of the controller, do both controllers behave the same?
Yes, same behaviour. In addition to that, I have checked the cable connections with my multimeter to rule out a broken line - both cables are find (no broken lines).

Have you opened the controllers and looked for any obvious faults?
I opened both of them to clean the contacts. During this, I did not see anything out of the ordinary.
I noticed two SMD capacitors. From my Commodore Amiga restauration experience, I know that caps like these might be faulty or even leaking despite looking fine from the outside. Is this a typical failure of the 3D Control Pads? Can they be replaced with ceramic capacitors, or do they require a electrolyte cap replacement?

Do you get anything unexpected if you measure the resistance between each controller pin and Vcc, or each pin and ground? If the "TL" pin is stuck high, it could cause a situation where regular 6-button pads work, but not any peripherals that used the 3-line handshake. Do you have a mouse, keyboard or multitap that you could test?
For this, I do not know which is "ordinary" (expected) behaviour, or which is the TL pin? Can you recommend a good technical doc where I could get that knowledge? The only service doc I found so far is a Sega Saturn PAL Model 1 service manual, but this does not have a pinout map of the joypad ports, or a troubleshooting guide.

I do have two multitaps I can use for testing purposes. What should I test?
 

antime

Extra Hard Mid Boss
Is this a typical failure of the 3D Control Pads?
Not that I know of. A controller should be a much friendlier environment though, no high temperatures and so on.

For this, I do not know which is "ordinary" (expected) behaviour, or which is the TL pin? Can you recommend a good technical doc where I could get that knowledge?
Have a look at the Yabause wiki. D4 and TL are the same pin.

I do have two multitaps I can use for testing purposes. What should I test?
Just that they work when plugged in on power-up. The multitap also uses the 3-line handshake protocol, so it could malfunction in a similar way. Have you opened up the Saturn yet?
 

Eidolon_NG

New Member
Hi @antime , thanks for taking your time to take me through this. Yes I have already openend my Saturn, see first post. As for disclaimers like @SegaSaturnShrine mentioned in my other problem thread - don't worry about it, I'm a pro in electronics (advanced degree in C64 and Amiga restauration), just a newbie in Sega Saturn restauration (plan to become pro though ;-) )

First, I measured the voltages arriving from the power supply board at the main board: 3,38VDC (Pin3) / 5,07V (Pin 4) / 9,16V (Pin 5)
--> everything seems to be normal here, power supply board OK.

Before doing more measurements, I tried plugging in digital and 3D controllers in various scenarios. I am observing a very, very interesting behaviour. Somehow it seems I can use one digital controller in one port to enable one 3D controller in the other port.

Scenario 1) when plugging in both 3D controllers in both ports before Saturn power-up
--> none of them works
--> with any re-plugin scenario, it stays that way (neither one works)

Scenario 2) when plugging in a digital controller in port 2, and any of my two 3D controllers (in digital mode) in port 1 before Saturn power-up
--> any of my two 3D controller in port 1 works from the start --> both my 3D controllers are fine, supposedly.
--> the digital controller in port 2 does not work from the start
---> the digital controller in port 2 does not work after re-plugin, because?!: Pin1 measurement stays at ~2,35V when plugged out

Scenario 3) when plugging in any 3D controller (in digital mode) in port 2, and a digital controller in port 1 before Saturn power-up
--> the digital controller in port 1 works from the start!
--> the 3D controller in port 2 does NOT work from the start
--> the 3D controller in port 2 does NOT work after re-plugin, even though?!: Pin1 measurement stays at ~4,99V when plugged out

Then I went on to measurements. The measurements are more or less the same for both control ports of the Saturn, give or take 0.01V
- The voltage on Pin4 is a bit lower than on Pins 2-3/5-8 - 4,85V instead of 4,99V
- The 5V voltage on Pin1 is not steady!
--- when no controllers are plugged in, it deteriorates steadily from 4,99V to about 1,xV, depending how long ago a controller in was plugged in
--- the Pin1 voltage on one port stays steady at 5V only if a controller (regardless of digital or 3D) is plugged in in the other port.

I conclude:

It is definitely a power supply problem of the controllers. Duh.
However, I am not sure which side - Saturn or controllers, or both.

--> Can I rule out a problem with my controllers? From Scenario 2, I think I can - both seem to work fine here.

--> If so, which part of the Saturn's control port power supply is failing? The controller port PCB also has electrolytic capacitors - could they be the problem, or is the problem located further down the road (on the mainboard, behind the flat cable connection)?
 

Eidolon_NG

New Member
Today, my Raphnet Saturn-to-USB Adapter arrived.
I can now rule out one thing: Both my 3D Controllers definitely works great when attached to a PC using the above adapter. Both in Analogue and Digital Mode.

So, it definitively is a problem with my Model 1 Saturn. I guess the next thing is that I have to dig deep into the available VA0 Service Manual and hope that there are enough similarities to my VA1 Board that

Also, I bought a cheap second Model 1 Saturn on eBay, due to arrive next week. Hopefully this one works well (at least it was advertised this way) so I have a reference device to test stuff against.
 

antime

Extra Hard Mid Boss
It's possible it's the capacitors, but it seems unlikely they'd both fail at the same time. Check F1 on the controller board (a fusible resistor I believe).
 

Eidolon_NG

New Member
HI @antime , how can I measure F1? ( I have never measured a fusible resistor before. ) Easiest would probably be to just order a replacement, if I knew what... I can't seem to find the part listed in the VA0 service manual, and can't make head or tails of the color rings (red or brown, dark gray, silver, silver, green). Further tips appreciated. :)

Also, I might notice that the fusible resistor looks well (not burnt out). Could it also be the capacitors on the board (47 pF) are faulty instead of the fusible resistor?

IMG_3016.JPG

I can measure the following behaviour of the Saturn controller ports:
- when Saturn is switched on, the ports measure only around 1.x ish Volts
- when a digital controller is plugged in one port, the other port measures stable 4.98 Volts
- when the digital controller is plugged out, the voltages in both ports steadily decline from 4.98 Volts down to 1.x ish Volts again
 
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antime

Extra Hard Mid Boss
The simplest way to test F1 would probably be to short it out. I'm not sure how to read the colour code, but I'm guessing 0.28 Ohm, with 10% tolerance and a 20 ppm/K temperature coefficient (the resistance corresponds to what I measured with my most accurate multimeter, but it's not calibrated).

In my last post I already agreed it could be the capacitors.
 

Eidolon_NG

New Member
Hi @antime , replacing F1 did the trick. I replaced it with a 0,5A picofuse instead of a fusible resistor. Should do as well according to experiences with a similar fusible resistor in Dreamcast boards.

Before that, I replaced the two 47pF electrolytic capacitors with 47pF ceramic ones - no success.

Well, at least I have a working Saturn again, and having replaced those elcos can't hurt either.
 

antime

Extra Hard Mid Boss
I once repaired a cheap camera microscope that showed similar symptoms. The voltages measured OK, and you could turn on the LED lights, but as soon as you tried turning on the camera unit the voltages crashed through the floor. The culprit turned out to be the 1W power resistor used as input protection. One of its legs had simply sheared off because of mechanical stress, but still provided enough contact surface to pass through a couple of tens of milliamps.

This makes me a little curious about how much power the different controllers consume.
 

Eidolon_NG

New Member
This makes me a little curious about how much power the different controllers consume.
Yes, it makes me wonder what caused the fuse in my Saturn to burn out in the first place.

The Saturn was heavily used for 10 player Saturn Bomberman sessions, having two 6-player multitaps and up to 10 joypads attached at once. (After all, that's what the Saturn was made for :) ).

Just maybe I have one or two "bad" controllers (or multitaps) which consume too much power, and caused the fuse to burn.

Having revived the Saturn now, the next steps is to cross-check my multitaps and controllers, while measuring the power flowing through F1. Maybe I can find the culprit then, and prevent another burn-out.
 

antime

Extra Hard Mid Boss
I doubt the fuse burned out, it shouldn't have conducted at all at that point (it'd be a pretty poor protection device otherwise!)
 

Eidolon_NG

New Member
Yes, but what was the problem then with my Saturn? Something must've been wrong with F1, because after replacing it with the picofuse, everything works fine now. :)
 
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