(Topic ID: 151503)

System 80b sound only works after pushing SW2


By Qmay

4 years ago



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  • 21 posts
  • 4 Pinsiders participating
  • Latest reply 4 years ago by mr2xbass
  • Topic is favorited by 1 Pinsider

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#1 4 years ago

Just obtained a free Raven (I paid too much I know).

Anyways, there's no sound on boot, red light is solid. Pushing SW2 makes all sound and music work and red light starts blinking.

Also display has garbage characters and sometimes doesn't turn on, not sure if related.

Any help greatly appreciated!

#4 4 years ago

Thanks! Will check it out and report back!

#6 4 years ago

Ok, spent a few minutes with the multimeter, I also followed a few instructions from pinwiki. FYI I had already done the ground modification in the cabinet (remove molex connectors, ground the wires to the metal frame).

So, checking the power supply board was fine, followed pinwiki instructions:

"When measuring the +5VDC provided by the power supply, first disconnect J2 on the power supply. Measure power at the J2 male headers first. Once within an acceptable range, turn power off and reconnect J2. Measure power across C1, the 100uf/10V capacitor that is next to J1 (power connector) on the MPU. The MPU may drag the +5VDC supply down a bit. If you find this to be the case, adjust the trim pot on the power supply until a steady +5VDC is seen at the MPU. Poor connections between the +5VDC power supply and the MPU board may also reduce the voltage measured at the MPU. "

So things I checked:
1) Voltage at J2 was ~5VDC, voltage at capacitor C1 was ~12VDC.

2) Then checked Reset pin #9 on A6P1 (connector on sound board), was ~5VDC (pushing the SW2 button had no effect on voltage at the reset line).

3) Unplugging display connector had no effect on sound boot.

4) Noted sound board dip switches were On-Off-Off-On (1-2-3-4), changed to Off-Off-Off-On since how they were depicted in the schematic (open open open closed). Not sure if I did this right, just seemed to me they should match the wiring diagram.

5) Noted that the A6P1 (connector on sound board) pin 12 and 17 are bridged, this is bridging the AC and DC ground as per wiring diagram, I assume this is okay, but not 100% sure there's not a ground loop or noise being introduced.

Any thoughts?

#8 4 years ago
#9 4 years ago
Quoted from mr2xbass:

When you checked the +5vDC coming off the power board, I assume you checked all the +5v outs? (I believe there are 3 or 4)

Yes, all pins were +5VDC.
And all info is of help, I appreciate it, even if it serves to confirm something is normal.

6) pin 40 on the 6502 chip (reset pin) was +5VDC, Vss pins 1 and 21 were +0.15VDC, need to check what they're supposed to be.

#10 4 years ago

Any other thoughts?

Things I plan to do now -

a. I need to confirm what the 6502 VSS voltages should be.

b. Check sound lines 1,2,4,8 should be high on boot, go low when sound activates.

#13 4 years ago
Quoted from Qmay:

b. Check sound lines 1,2,4,8 should be high on boot, go low when sound activates.

All pins were high on boot.

I did notice that when I bumped into the cables coming from J2, I heard definite noise in the board and I think even triggered some coils to fire like in a ball search. I think the connecter J2 may be crap, so I need to find a good way to replace it. Will reflow solder pins too.

#14 4 years ago

Haven't had a chance to work on it much this week, but did notice during a quick game that the music doesn't always boot but the sounds work every time (after sw2 push). Power cycle eventually brought music back. When music didn't work, opening coin door started music in attract mode, but music was gone in-game.

I'm going to fix J2 as mentioned above, there must be something to the fact that power cycling changes behaviour. Same for the garbage display, it's different between boot ups. I ordered replacement chips for the display as well.

#15 4 years ago

Did a reflow on J2 pins and took molex apart and rebuilt after checking crimps (seemed good).

This fixed my display! Sound is still having same issue. Lesson learned: reflow J2 regardless of how it looks. I'll repeat with J1 as well.

#17 4 years ago

The reflow on the J2 pins and rebuilding the molex connector fixed my display issue. I used a pushpin to "unlatch" the individual wire connectors from the white plastic molex. Then I stretched out the loop part of each wire connecter to hopefully provide better contact to the pins. This part literally took 1 minute to do. After removing the power unit, for the "reflow" although not a true reflow per se, I used my soldering iron to heat the pin on the back side to melt the surrounding solder and added a drop or two of new solder. Fyi for anyone out there, it's not sufficient to just heat the solder by touching the iron to the solder, you need to make a good connection by getting the pin hot and having the solder melt due to the pin's heat. This is really the case for all good solder joints - don't heat the solder heat the medium.

1 week later
#18 4 years ago

No luck woth J1 reflow, not sure where to proceed

#20 4 years ago

That's a good lead, I will check again now that the MPU pins are reflowed. I did at one point disconnect the display and that didn't help, so I have a feeling that it might not work...we'll see.

Also I need to double check that I did indeed check sound line 16 on startup.

I'm going to ask around locally to see if anyone has an 80b I could out my sound board in, that will at least narrow it to a sound board issue or something else.

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