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Title: Hyper Olympic bootleg #2 repair log Post by: Zabanitu on January 14, 2012, 11:04:43 AM 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 Title: Re: Hyper Olympic bootleg #2 repair log Post by: channelmaniac on January 14, 2012, 02:27:52 PM 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 (http://pdf.textfiles.com/manuals/ARCADE/A-J/Hyper%20Sports%20)[Schematics]%20[English].pdf RJ Title: Re: Hyper Olympic bootleg #2 repair log Post by: Zabanitu on February 28, 2012, 07:07:35 PM Hi,
finally i fixed the board :72- 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 |