(Topic ID: 176447)

Testing DE sound board

By RoyF

7 years ago



Topic Stats

  • 6 posts
  • 4 Pinsiders participating
  • Latest reply 7 years ago by Schwaggs
  • Topic is favorited by 3 Pinsiders

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#1 7 years ago

Time to finally solve a long standing issue with my DE Star Wars. To do that I need some advice on how to measure power at the sound board with the sound board "in circuit".

Symptoms - Sound cuts out during play, and sound goes wonky like the sound board is rebooting ("May the Force", or shorter variations like just "May The" repeated multiple times). Worse now, sometimes the sound board doesn't finish booting at power on (hear the full "May the Force be with you", or something shorter than the abbreviated phrase that should normally be heard at boot, without music). Running original ROMS, not the upgraded version (but do have the upgraded ROMS from Chad available).

I measured voltages at the power supply board test points and see (after things stabilize and the machine warms up for 20 seconds or so):

12+ = between 11.83 and 11.87, goes to 11.67 if I start a game and leave the ball unlaunched (R2D2 head moving and Deathstar moving).
12- = 14.95
5+ = 4.99 (but measured lower when booting the machine from cold, maybe 4.7, then rose until finally stabilized at 4.99).

I'd like to use my DMM to measure power at the sound board with the machine in attract mode, and when powering on the machine. What would be the best way to do that while leaving the sound board in the circuit? Where would I put the red meter probe on the sound board?

Possibly unrelated, I could swear I see the Deathstar "stutter" a bit when it first starts rotating, but maybe it always did that.

#2 7 years ago

The capacitors on the power supply are probably going bad. The voltage should be in spec on power up and not gradually change. I had a similar problem with my Lethal Weapon 3 which I think is the same power supply. Try replacing Capacitors C1 C2 C7 or any others that are associated with the 5 volt and 12 volt circuit. C1 and C7 get a lot of heat from the big aluminum heat sink and is a common problem on Data East power supplys. I believe the sound board uses 12 volts or -12 volts and regulates it down to 5 or -5 can't remember for sure but it seems like your not getting proper voltage to the sound board. Probe the connector with your meter on the sound board to get voltage readings. There may be a connector not making good contact. Hope this helps you good luck.

#3 7 years ago

Check power supply and connectors and circuit board solders and headers. Very common problems in DE pins. Report back with voltage readings.
Good luck

#4 7 years ago

Ok, fresh set of measurements.

Measurements taken in attract mode. Ground lead connected to ground test point on power supply board for all measurements.

Power supply board at test points:
-12v = -14.99
+12v = 11.86
+5v = 4.99

Power supply board at CN6, measured on the female connector while connected to the male header:
-12v = 14.98
+12v = 11.86
+5v = 4.99

Sound board at CN2, as measured on the female connector while connected to the male header:

-12v = 14.96
+12v = 11.82
+5v = 4.77

Sound board at CN2, as measured on the female connector while connected to the male header - after removing and reseating CN2:

-12v = 14.98
+12v = 11.84
+5v = 4.90

Sound card booted and played properly after reseating CN2, at least for the couple of games I played. No rebooting, normal speech and music.

Conclusions:
1 - Low +5v at sound card is causing the sound board problems.
2 - Since reseating the CN2 connector improved things, will remove and replace the CN2 header and replace the CN2 female connector.
3 - No need to rebuild CN6 on power supply board as power supply test point voltages are virtually identical as measured at the female CN6 connector.

Question - Why would the +5v have measured low at the CN2 connector? Would make sense to me if it had measured low on the sound board itself, but measured low at the CN2 female connector while connected to the header and improved when the CN2 connector was reseated. That doesn't really make sense to me since I think what was being measured was the +5v being delivered by the harness to CN2, not after the less than ideal connection between the CN2 harness and the CN2 header. I can't argue with what I observed, which was that the problem cleared after reseating the CN2 female connector, but just want to understand better. Hmm, maybe the issue could be in the CN2 female IDC connector, a less than ideal connection between the +5v wire and IDC connector that improved after movement of the connector during reseating??? If that is the case, rebuilding the CN2 female connector might be all that is needed.

Question - is the -12v = -14.99 measured at the power supply test point a value that is out of range, and if so what would I replace on the power supply to improve that?

One more thing of note. Meter on power supply board +5v test point shows +4.99v reading immediately upon power up now. Only showed the lower value that drifted upward to 4.99v the first time I powered it on (had been off for months). Should I still consider replacing C2 on the power supply board and/or other caps there, or (as I'm thinking) just make the CN2 repair at the sound board and then see if any problem remains?

#5 7 years ago

Reseating connectors will many times solve weird little problems. I wouldn't mess with that connector any more unless the problem reoccurs.The -14.99 volt reading is ok because it is not regulated. I think the sound board regulates it down to -5 volts. Replacing the power supply caps like C2 & C7 is cheap insurance against future 5 volt problems. They will eventually start leaking and eat up the board traces and kill the 5 volt circuit.

#6 7 years ago
Quoted from RoyF:

Question - Why would the +5v have measured low at the CN2 connector?

When measuring the voltage on the IDC connector, you are measuring the voltage at the female connector metal contacts. This measures any voltage drop between the header pin and the IDC metal contact. It does not measure the voltage drop between the IDC connector metal contacts and the wire. The electrical connection with the wire is often worse than the connector to header pins. Every removal and insertion cycle stresses this connection, especially when people pull on the wires to remove them!

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