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lastspaceship

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Hi -
Have a 2p simpsons PCB which was working ok (apart from no sound through the jamma) - went into the settings changed the sound to stereo then it has got stuck on a 12c Bad rom error, reversing the screen stuck in loop. Read about trying hold test on startup, no joy so far. Appreciate suggestions, not experienced on fixes etc,

12cerror.jpg


cheers matt
 

djsheep

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That repair log answers your question. You’ll need to pull that chip and replace it.
 

lastspaceship

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thanks, appreciated. i read elsewhere a case where the chip was actually ok, just kind of needed re-intialising. looks like it might be the fix route.
 

ShootTheCore

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Remove the ROM chip, blow out the socket, and give the legs of the ROM chip some light sanding with an emery board. Reinstall the ROM chip, power up and cross your fingers.

If it still fails the diagnostic check, you may have to replace the ROM.
 

AlxUnderBase

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Matt, 12C is a ER5911 . Like what Caius wrote in the repair log , the best way is to probe it or check it with an IC tester if you have the posibillity to do that to see if is indeed that you need to replace on your pcb :happy:
 

lastspaceship

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ha, all help greatly appreciated all. don't have the kit to probe etc but at least i can see the path to sorting it. One thing i'm checking is im actually doing the re-initialisation attempt right. Connected via a supergun. ie power off> press test (on PCB) hold > power on > hold(20seconds or so) > release. Hopefully marge can get back to knocking people out with her hoover soon.
 

lastspaceship

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20 seconds is too much sir ... she take around 5 seconds to initialize the roms ✌️
thanks for the tip , been trying shorter time. it flashes this message while i hold test and then when i release back into the inverted loop rom check with bad 12c. maybe can't test button my way out of this one!

bad eeprom.jpg
 

djsheep

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Nice taste in records there bro... Mike Nock, Oliver Sain, Andy Bey, Johnny Jenkins :)

Assuming you’re a beat head? Hit me up @lastspaceship
 

lastspaceship

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Just to summarise this one if anyone has an issue. follow the suggestions from those who know what they're doing above. In my case i guess eeprom was ok. I did read that ER5911 stores settings, and i (maybe) caused this by adjusting settings then possibly (though i don't recall) pressing test which caused some issue with the eeprom getting stuck somehow - so just watch out playing with test and settings maybe - and persevere with the re-intialisation - after that into following the proper diagnostic fix advice above or get help! thanks for assistance all on here. helpful. cheers, matt

simpsons.jpg
 

channelmaniac

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There are a couple of chips that gate the access to the EEPROM. If they are Fujitsu, they are suspect and should be changed before you try changing the ER5911.
 

channelmaniac

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Here's what you need to check... the LS174 at U6, the LS257 at U20, and the LS257 at U21. Beware that there are at least 2 revisions of the Simpsons PCB so don't be surprised if the U numbers don't line up. Use a multimeter and you can quickly ID which chip is which by their connections.
 

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lastspaceship

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Much Appreciated - yeah don’t think the u’s match on mine. Sorry for basic question, Prob need to step up my kit, you’re saying test these with logic probe right ? Haven’t got too far into testing socketed EEPROMs. Matt
 

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channelmaniac

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Yes, logic probe. They may look dead until the chip is being read or written to so you may have to 1) power cycle the board and keep testing... and 2) use the "Memory" switch on the logic probe to capture very fast signals.

This is where a logic probe with audio beep rises above a regular logic probe. The beep helps a lot.
 
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