No ADPCM on X68000 compact....! SOLVED!!!!

[gypsie]

Hello everybody, need some advices,

Got an issue with my X68000 who have stopped playing Adpcm sound suddently . My computer was running very well before.

I ve tested few games , music is ok but pcm sounds are missing.

For exemple, no sound with final fight and arkanoid, only music.

I ve recapped the audio section.

I will try to change IC7 according to this guide : http://www.gamesx.com/wiki/doku.php?id=x68000:x68000_xvi_compact_audio_troubleshooting_and_repair

I ve purchased 2x  MC3403 chips on ebay, must have them this week.

Picture of the moterboard, audio section :





Do you think that do the IC7 replacement could be the solution ?

Thank you very much.

[kamiboy]

Impossible to say. You need to follow the signal from the source to see where exactly it stops.

[gypsie]

I ve got the advice to "listen" DAOUT on  OKI MSM6258 with audio probe . Do you know how to do audio prob or external amplifier ?

[kamiboy]

No. I would use an oscilloscope, or measure voltages from the output pin. No voltage, no signal.

[gypsie]

Thank you i will try that before removing IC7

[gypsie]

Hello,

I'm trying to test OKI MSM 6258 (IC32) .

I need to "listen" DAOUT on pin 22, i ve no Audio probe so i use a small Hearphone .

So i soldered 1 wire from the hearphone to PIN 22 on MSM 6258.
Next, i soldered second wire from the hearphone to PIN 30 on MSM 6258 ( VSS2  analog ground pin).

picture :

I've started the X68000 with a game using adpcm sound but sadly i can't hear nothing coming from my hearphone??!!!!!

So my question is, do i have well connected my hearphone to the OKI MSM 6258

Thank for your help!

[caius]

The approach is right but I don't know if the MSM6258 used on X68000 is set to use the internal DAC or an external one.Datasheet here:

http://datasheet.datasheetarchive.com/originals/distributors/Datasheets-112/DSAP0054035.pdf?_ga=2.233167960.751463458.1505397753-1410871685.1505397753

If set to use an external DAC then it's normal you can't hear anything on pin 22 (in this case pin 18 'DASO' is used to carry PCM serial data to an external DAC).Anyway, in both cases you have to check if data is present on input.So, with a logic probe or oscilloscope check if you see activity on D0-D7 pins.Obviously check also if clock is present.

[gypsie]

Thank Caius!

I ve tested pin D0-7 with my logic probe = HIGH on all pins.

I ve put my logic probe on pin 22 and 18 = HIGH  ( My logic probe have a audio output, but can't hear sound)

[gypsie]

So now i don't really know where to start.

First, i will replace  MC3403 on IC7 ( more easy to remove). Hope to solve the issue ....

[caius]

The MC3403 is a OP-AMP (so an analog part) which amplifies the converted signal from the internal OKI MSM6258 DAC (or from external DAC) so it comes after.
If you say that data lines of the OKI are stuck HIGH then the problem lies in the digital circuit and not analog.

[gypsie]

ok so i will replace oki msm6258, just more hard to remove. But i need to find a new one and can't find it on ebay....

[caius]

Replace anway first the  MC3403.If you don't solve, you can try to replace the MSM6258 but honestly I don't think it's the culprit.You should figure out why data are absent.

[gypsie]

You don't think that the MSM6258 is the culprit ?

[caius]

Probably not but I can't be sure without the hardware here with me.Did you also check if +12 and -12V are present?Is the ADPCM sound missing both on speaker and headphone output?

[gypsie]

Yes missing on.speaker and.headphone.

12v not tested. I.will test.voltage tomorrow.

Thanks

[gypsie]

News 17/09/2017 :

Replaced IC7 MCM 3403, Sadly adpcm always missing...


Have done some tests with some games :

- ARKANOID : no sound when the ball hits the wall . But i can hear a very little " crack" when the racket is detroyed ( when losing the ball)
- AtOMIC ROBO KID : The game crashs when the robo is hitten (and so destroyed^^).  I think that a adpcm sound is played when the robo is hitten.
- FINAL FIGHT : absolutely no sound during game.

I think really that OKI6258 must be dead.

What do you think about this

Thanks very much.

[gypsie]

Does anyone know information about this part (ADPCM PWB )?



Thanks

[gypsie]

NEWS 23/09/2017 :

MSM OKI6258 is the culprit!!!!!

I ve tested with my logic probe pin 22 (DAOUT)  on the OKI on a WORKING X68000, and i can hear the adpcm sound through the logic probe.


So now my question is: is there something to test placed before the OKI chip, or OKI is dead???

Thanks

[neko68k]

I guess the next question is, is the OKI getting data from RAM and/or are the control signals from the 68000 getting there.

[gypsie]

Yes tested D0-D7 with the logic probe, signal.is here. So Oki is.dead.

Sadly, not very easy to find/ buy a new one. ..

[gypsie]

REPAIRED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


OKI MSM was faulty!!!!!

[gypsie]

Old OKI MSN removed :



First difficult was to find a new OKI chipset. Only Rantle east electronic have them in stock.

New OKI  soldered:



Adpcm sound bring back to life


I ve another X68000 compact with low Adpcm sound. I will try change the OKI

[neko68k]

nice. way to go 

[caius]

Many thanks for giving credits to me for this repair!!!Stupid me that I guided you remotely and privately.Next time I'll send you an invoice...

[gypsie]

Yes Caius, thank you for helping me. You're not forgotten don't worry 

[caius]

A simple 'thanks' is worth more than one million of $$$, I'm glad you fixed it.

[gypsie]

In summary :

No adpcm sound :

- With logic probe, test OKI MSN 6258V IC35 pin22 DAOUT => if no adpcm sound , test D0-D7 ( Pins 4-3-2-1-41-40-37-36 should be pulsing).
IF D0-D7 pulsing => OKI MSN must be replaced.


Perhaps Gamesx wiki could be updated ?