Hyper Olmpic (Track and Field) PCB repair

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Dec 082020
 

I’ve had this Hyper Olympic board sat in my repair pile for more than 5 years.  I kept coming back to it, but never really made any progress, mainly because the schematics are poor.

On initial power up I got jumbled sprites for the runners and lines through the background, text and logos

I took a video back in 2015 here:

It was originally labelled a Hyper Olympic board, so I thought this might be why the logo was messed up so I changed it from a Track and Field to a Hyper Olympic, but that wasn’t the case and the issue persisted.

I also used ShoeStrings test rom at the time to see if it could identify any issues and unfortunately this did not help. Here is a video:

I used my logic probe back in 2015 and looked through the board and noticed some stuck pins on two of the eproms between 11C-15C, and traced this back to a faulty LS04 @ B6.  I swapped this out and the runners were back.  The only issues that persisted was the lines and faulty logo. I took a video here

Fast forward to the end of November 2020, and I picked this up again.  The background and text were missing details and the logo had wrong colours and there was jailbars as in 2016.  I was fairly confident the problem was around the roms D10-D12 @ H14-16 and the 273 @ 14G was the next part in the chain.  I took at look at that but found no issues.

If I removed D10-12 and the two rams @ 11-12H I could still see lines on the screen, so I came to the conclusion that they were not affecting the lines.

I had a look on the scope and again didn’t see anything obvious.  I spoke with a fellow collector and he suggested that I started to short pins to see if I could narrow the area a bit.  This is where I got my break through.  I started to ground the data pins on the D10-D12 roms and found that if I grounded the D0 pin on the roms I could replicate the issue.  This narrowed the problem potentially down to 2 chips:

My money was on the LS273 because it was a Fujitsu, so it was the first one I changed. Sadly the issue persisted. So I then decided to also change the LS157 @ 15G as I was confident the problem was definately here. I am glad I did because I powered on the board and was glad to see the ongoing 5+ year long board was now fixed!