X68030 - Joystick and audio problem

[costa]

Hi, here I am back with one more challenge to myself and the friends who want to contribute with ideias and suggestions.

I replaced all caps on my X68030 - daughter board, motherboard, video module.
There was clear signs of leaks on the daughter board (wet), and some signs on the motherboard.
There is no visible corrosion.

I plugged a XSIMM10 and one Midi board on the computer, and booted the memtest68k disk.
Memory test is ok, and keyboard works, games boots and I can play.

However, there are these two noticeable issues:
1. No audio on the speaker or headphones.
However, using a SCART video cable, there is audio on television.

2. Joystick 1 do not respond for right/left moves.
Joystick 2 works fine, I can play games and move the character on all directions.

I am looking at the schematics for the XVI and X68000, but they do not seem to be the same as the X68030.

Any suggestions on how to sort this problems out? Which schematic I can look, or which components to test ?
thanks

[eidis]

 Hi Costa !

For the audio problem, this could give some hints:

X68000 XVI Compact audio troubleshooting and repair
http://gamesx.com/wiki/doku.php?id=x68000:x68000_xvi_compact_audio_troubleshooting_and_repair

For the joystick problem, I once had a similar problem with one of my arcade PCB's. Try tracing the bad signals to the first IC and tell me which chip is it.

By the way, we have a very comprehensive service manual for the 68030, courtesy of BlueBMW and Lydux. There are schematics starting from page 72 as well.

X68030 Service Manual
http://nfggames.com/x68000/Schematics/CZ-147%20-%20X68030%20Service%20Manual/CZ-147%20-%20X68030%20Service%20Manual.pdf

Keep the scene alive !
Eidis

[costa]

Eidis

I am trying to follow the track, will let you know later.

I have noticed the following behaviour also:

Although the keyboard works perfectly wen boot HumanOS, it does not work well when I boot a game.
For example, I can move up/down through the menus, but not right - as when switching resolution, we need to press K - it does not work.

If I plug the joystick with the game booted already, it is like it move to the right, and when the game ends, it automatically clicks to "restart"... Looks like the ir a short circuit on the lines for right/left...
Maybe this can be cause by a bad resistors? (pulldown or pulp?). The joystick lines on the X68030 connects first to a resistor network... just guessing.

On the XVI schematics, the joystick ports also has a resistor network first, then connects to IC217 (which is a 8255 peripheral controller).
On the X68030 daughter board, IC217 is the YM3012 (but I have not verified yet if it is connected to the joystick ports).

And by the way, about the X68030 service manual, unfortunately it is for the compact model only (CZ-300), which has a different schematics than the CZ-500 (the model I am working on now is the double tower 68030).

Cheers

[costa]

I tracked the pin 4 trace on the joystick 1 (right movement). I it passes through the resistor network RM208 and and ends up on IC228 - which is the 8255.

No sure what to do next.

[eidis]

 Hi Costa !

The resistor network is probably good. You can confirm this by desoldering it and testing it with a multimeter. It looks like the prime candidate for replacing would be the NEC 8255 which is a parallel controller used for printer and joystick. eBay has plenty of them at dirt cheap prices. Don't forget to put a socket after removing the old chip. By the way, it could be that the chip is still good but somewhere close a trace is broken. Test for continuity to confirm this.

More info can be found here:

Intel 8255
http://en.wikipedia.org/wiki/Intel_8255

X68000 Generic Chips
http://gamesx.com/wiki/doku.php?id=x68000:generic_chips

Keep the scene alive !
Eidis

[costa]

Hi,

I did find find problem in the traces, and not sure I can replace smd components...
Any way, after verifying the traces, I measured the resistor networks next to the joysticks 1 and 2 and got the values below.
Note that Joy 1 has problem on the right/left signals, and I did not test trigger 2.
Joystick 1 works fine.

The anomalous values on the resistor coincides with the pins with problems.
Might that be a problem in the resistor, or could it be on other part of the circuit? Last resort is to remove components to test, but I am trying to avoid that ...

Joystick 1
Pin1 (forward) 22,9 K ohm
Pin2 (backward) 22.9 K ohm
Pin3 (left) 20.4 M ohm M ohm
Pin4 (right) 20.4 M ohm
Pin6 (Trigger 1) 22,9 K ohm
Pin7 (Trigger 2) 20.4 M ohm

Joystick 2
Pin1 (forward) 22.9 K ohm
Pin2 (backward) 22.9 K ohm
Pin3 (left) 22.9 K ohm
Pin4 (right) 22.9 K ohm
Pin6 (Trigger 1) 22.9 K ohm
Pin7 (Trigger 2) 22.9 K ohm

[eidis]

 Hi Costa !

Try desoldering resistor network which is connected to joystick1 port and measuring it out of the circuit. Are the values for pin3 and pin4 still abnormal ?

Keep the scene alive !
Eidis

[costa]

I tried... not very hard, but just enough to see how difficult it is going to be to remove that array...
I will just let it got for now, since this seems to be hard to troubleshoot and fix, and I am still learning a lot about these machines, and still refining my soldering capabilities.

It would be nice to have this machine 100% working now, but I have others that I think is easier to repair, or only a matter or replacing caps, so I will skip this one for  a while.

Thanks Eidis for the help... I should get back to this in a few months...

[costa]

I have just repaired the joystick problem in the X68030.

Indeed, the resistor network connected to the controller port 1 was half burned, presenting infinite resistance in some of its terminals, and affecting pins for right/left/button 2.
I could not find a replacement for the resistor network, so I used three resistors connected to the failing pins and the computer is now usable! Both ports working.

I sill have to look the sound problem tough, but the moral is much higher now!

[eidis]

 Hi Costa !

Congratulations on a job well done ! I think I might have a solution for your audio problem. As you can see in the attached picture, the audio which goes directly to the RGB port is not amplified. So this strongly suggests that your X68000 has fried op-amps. There should be two MC3403 (Quad Low-Power General-Purpose Operational Amplifier) or something similar near the headphone jacks.

Keep the scene alive !
Eidis

[costa]

Eidis,  I think you right... I will focus on those amplifiers, but I am really afraid because they are smd, and If I have to replace them... oh no!

[eidis]

 Hi Costa !

Desoldering them will be the most difficult part. You can cheat by cutting off their legs with micro cutter or something similar:

Micro cutters NZ-12 ENGINEER
http://global.rakuten.com/en/store/kys/item/en-nz-12/

Then use solder wick and a soldering iron which has no more than 15w of power to remove the remaining legs and excess solder. Clean the solder pads with isopropyl alcohol and q-tips. Then evenly tin the pads and solder the new op-amp in place. Try to solder the legs so that they do not stress/tension the pads and do not lift them off with time.

P.S. Do not heat the pads with soldering iron for more than four seconds.

Keep the scene alive !
Eidis

[costa]

Hi Eidis,

I use this technique for the smd caps, but have not thought of using it for those small CIs.
If I come to a conclusion that they need replacement, I will do it this way as I am not confident of using hot air to remove it deu to the board density (i.e, too many components and too close to the CIs).
I am thinking that maybe there is a track interrupted or something like that, so I will investigate a little further.

thanks