WPC sound board problem (A-12738)**FIXED**

[lilshawn]

I got this Gilligan's Island machine on trade, everything works except the sound. The board was acting totally dead. No bongs on boot no static nothing.

all volts are there. ribbon cable good. EPROMS good (match 100% to bin file)...have a working board from another pin and it works fine. soooooo speakers and wiring are fine.

changed the amp chip, nothing still. changed the 2 74ls374 chips by the input of the data cable (u29 u30) and 2 op amps  TL084 (u8 and u7 i believe) replaced the bridge diodes and caps just in case. still nothing.

i swapped the main cpu and the 2 yamaha chips from the working board and also a non-working board(with an unknown problem), and i can get some static noise (varies) and a few random burps out of it when it first boots up, the quiets down after about 30-45 seconds.

sound test yields no change in static. I'm not getting and errors or anything on the display.

[rusolinio]

check this guide out. Its considered the bible in my home these days.

http://www.pinrepair.com/wpc/index3.htm

[lilshawn]

Insert Quote
check this guide out. Its considered the bible in my home these days.

http://www.pinrepair.com/wpc/index3.htm

yyyep...done it all, i'm thinking it may just be easier to source a new one on the ebais and be done with it...it's too old to put on location so someone can buy it and put it in their basement.

[lilshawn]

still trying to get this unit operational. the volume chip is good and the amp has been replaced.


does anybody know where or what generates the diagnostic "bong" noise? i believe it's a chip generating the sound (not ROM based) but i'm getting nothing.

[lilshawn]

would anybody believe me if i said i have sourced and replaced nearly every chip on the board and the * word describing sexual relations * thing STILL doesn't work.  replaced all but 4 chips now. 8 mhz and 3.57 mhz clock signals I believe are good. on the oscilloscope it's there, it's timed properly, and at a proper voltage level, the 3.57 mhz just a little ugly. i think it's just a result of the weird high low inverter (3 of them?!)  it goes through,  i'm going to replace the resistors and small caps in the 3.57 mhz circuit to be sure.

fed the amp an audio signal directly and it plays (amplifies) fine.


 

starting to get a little frustrated with this board. 

[lilshawn]

A known working board from another pin works 100%. Swapped the processor, and the 2 yamaha fm chips and confirmed them working.

Bypassed the electronic z-pot so that's not the issue. Have some digital to analog converter chip to replace the DAC sound chip, but unable to source the voice convertor.

But since we have audio from 3 different areas and nothing from any of them, I'm inclined to belive something has gone sideways with the communication between the CPUs. Still unsure about the reset line, seems the circuit is randomly going low (possibly resetting the cpu) still searching.

Still banging my head... Time for sleep things are getting blurry

[lilshawn]

Okay, we have a bad static RAM chip (U9). turns out the chip was causing the CPU reset line and it's associated circuit to randomly dip low causing the CPU to be in a continual state of limbo. (tested with logic probe and oscilloscope at pin 37 of the 68B09 CPU should read high, was reading high/low/pulse indicating was being pushed into reset continuously)  The Main CPU must have been timing out and giving up waiting for the soundboard CPU to become active.

only found it after finding out that my EPROM programmer (which i was using to burn a set of sound ROMs to send the soundboard out for repair) will also test 74 series chips and also SRAM...SWEET! after testing all the 74LSXXX chips and found them to be good, i removed the 6264 SRAM chip at U9 and tested it. BAD!

pulled a working SRAM chip from an old board and we are back in business. if anybody thinks any other info i can add that would be helpful in assisting someone else, i can add it.

[Ken Layton]

I'm working on one of these sound boards in an Addams Family.

Just tried swapping in a known good 6264 ram chip and it did not fix mine.

Back to the drawing board.

[Ken Layton]

I have even swapped in brand new crystals on this one and it still doesn't work. I give up on this board so I'm shipping it off to K's Arcade for repair.

[lilshawn]

Good try. Sometimes  the 78hct250? 257? ...Chip (right next to the biggest ribbon cable) goes bad. It handles the data in and out of the cable and is fairly susceptible to static.

[Ken Layton]

Tried replacing both U29 and U30. Both are 74LS374 next to the data input connector. Did not work. Same results: no audio. So off the board goes to K's Aracde for repair.

[lilshawn]

huh.  well, let us know what it was they end up fixing.

[Ken Layton]

Just got the board back from repair. They replaced chips U21 and U28. Addams Family now has sound!