Hyper Olympic bootleg #2 repair log

[Zabanitu]

board displayed garbage on screen.
replaced LS244 @7D then i had all OOOO on screen.
replaced LS138 @3E board now runs fine.
sound is dead though..... anyone has ideas?
the sound Z80, 6802, and 6821 PIA are working fine (by substitution).
i just ahve the SOUND_ON signal wich triggers the /INT pin of the Z80, then the /IOREQ pin goes low but never recovers from that. in a good board the /IOREQ pin would go low after SOUND_ON and then hi again after the sound has been played this resets the /INT generating flipflop.

help would be welcome

[channelmaniac]

Since this is still a work in progress it has been moved from the repair logs section.

Working on a bootleg can be tough because there are very few schematics available for them. I'd start troubleshooting this one like any other board:

Check the ROMs for the proper checksums. Verify the RAMs are good. Are the ROMs and RAMs being selected properly (/CE and /OE signals) is the R/W signal to the RAM working? Are the sockets/pins on the chips OK or are the corroded?

Next check the output of /IOREQ and /M1 as on the original Hyper Sports/Hyper Olympics those feed into a 74LS02 then into another one along with the reset signal, and then through a 74LS74 back to the /IRQ pin.

http://pdf.textfiles.com/manuals/ARCADE/A-J/Hyper%20Sports%20[Schematics]%20[English].pdf

RJ

[Zabanitu]

Hi,
finally i fixed the board   

some weeks ago i've started shotgunning all the TTL ICs on the sound board but soon got frustrated.
this night i just continued replacing the LS367 @ 5B and hey presto the sound came back.
The CPU was probalby stuck waiting for something on the data bus (maybe counter data on D0..D3 coming from LS393 @ 6B) and it nevere reasserted the /IOREQ line wich resets the /INT flip flop @ 2A)

i knew the DA converter 76489AN worked because i tested it into another board; the rest of the system (EPROM, RAM, address decoding) worked fine because the Fluke 9010A told so!

patience is never enough when fixing this old pcbs !!!!

@Channelmaniac:
now i think you can move this thread to the repair logs.... Thanks