RoadBlasters Help

psu00427

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Hello. Long time follower, first time poster.

My RoadBlasters was working fine until one day I fired it up and got this jumbled mess.

- No changes if I switch it to test mode.
- I've checked the voltage at the power supply and various contacts on the main board and cartridge and all check out at +5V.
- Unplugged all Molex connecters and plugged them back in.
- Reseated most of the ROMS but nothing changed.

Any thoughts? Thanks!
 

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do you have a logic probe?

first thing I'd check (after what you've already done) is to make sure your still getting clock signal at the CPU.

after that I'd test the memory and, however that will be difficult to do unless you can take it out of the game itself and lay it on a test bed so. It also really helps to have a fluke 9010 or similar as that makes life sooo much easier.

it doesn't hurt to test the ROMS either if you have a EPROM programmer.

-brian
 
Re-seat the boot roms below the main CPU. As the previous poster stated, if that doesn't work, *check 5v supply at the boot roms/CPU*, check to see if you've got a valid clock signal at the main CPU. You can also check to see if your CPU is running.. but your screen shot seems to indicate that it just didn't initalize/boot. Honestly you wouldn't even get a valid video/sync signal to the monitor if your clock circuitry wasn't working in some capacity.. doesn't mean it's getting to the CPU though..
 
Thanks brzezicki / akeym. I don't own a logic probe, EPROM programmer or Fluke 9010 yet but I will try to re-seat the boot roms below the main CPU.
 
do you have the newer small AR board in this? sometimes a flaky one will make this happen. check the voltages on it. make sure the connectors are good (i re-flowed mine for fun)

there are multiple connectors...at one point also unplugging one of the connectors prevented the game from booting and the garbage screen occurred as in your picture...forgot which one.
 
Thanks advans13. Not sure if the board I have is a newer version of it. Attached is the one in my cabinet. Where on the board is the best place to test for power? I checked several places and wasn't getting a reading but I don't see a specific test place like on the main/cartridge.
 

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Hmm.. apparently the bridge rectifier on the audio board feeds the main cpu board.. learn something new every day! If I read the schematics correctly this portion of the power supply is used to (among other things) trigger power-on reset and get the CPU started.

In any case, advans13 has a good suggestion, and is probably referring to the connector labelled JACDC a 9-pin connector on the lower right in the picture you provided. The AC coming into that board is fused, so I'd check F2,F3 to make sure they aren't blown. Then check between pins 6,8 and 6,9 for 12vac. If you've got input, check the dc output on pins 3,5 (+14vdc) and 1,5 (-14vdc) - pin 5 is ground.

See the schematics for wiring: http://arcarc.xmission.com/PDF_Arca...rs_SP-298_1st_Printing_for_System_1_Games.pdf
 
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