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solved
- Thread starter darren_ross
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Maybe a failed component upstream? I had similar on a WPC game and replacing the chip for the row sorted it. Sorry can't be more specific.
I'm thinking @ SgtGrizZ could be right on this, I also have had this twice on a DE machine it went further than the transistor
I'm assuming that you have replaced Q76 and associated diode If you have the schematics to hand in the manual check if Q76 traces back to a 74LS240N chip on the board or something like that a 74 family I/C, I vaugely remember that may be the one I replaced, @fintanstack may be of help here he currently has the machine if he has a look at the mpu board and can see the two socketed chips and identify them for us it may be of help.
I know this is a Sega not DE but the board architechture may be similar as they were the same manufacturer all in all.
I may be completly wrong on this if anyone else has any ideas please jump in and help Darren out
I'm assuming that you have replaced Q76 and associated diode If you have the schematics to hand in the manual check if Q76 traces back to a 74LS240N chip on the board or something like that a 74 family I/C, I vaugely remember that may be the one I replaced, @fintanstack may be of help here he currently has the machine if he has a look at the mpu board and can see the two socketed chips and identify them for us it may be of help.
I know this is a Sega not DE but the board architechture may be similar as they were the same manufacturer all in all.
I may be completly wrong on this if anyone else has any ideas please jump in and help Darren out
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Ok that was a stab in the dark if you can find Q76 on the schematics does it go back to any legs of these chips. I have no access to the electrical schematic drawings so I am really guessing here.
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Hmm interesting I have 74LS08 chips here I usually buy more than I need... are they 14 pin chips on your board?
...I don't know if they are the same.
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...I don't know if they are the same.
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Ok Darren thanks for the pictures unfortunately I can't read the characters on the electrical drawings.
I'm assuming that Q76 is below the resistor bank in the board picture also the chips have no U numbers identifying them.
As far as I can tell DV7480N and 74LS08N are the same both Dip I/Cs
It may be the case that whatever spiked the transistor may also have affected the chip that's what happend on my old machine.
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I'm assuming that Q76 is below the resistor bank in the board picture also the chips have no U numbers identifying them.
As far as I can tell DV7480N and 74LS08N are the same both Dip I/Cs
It may be the case that whatever spiked the transistor may also have affected the chip that's what happend on my old machine.
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I would really need to read the schematics Darren but on IPDB they only have a part manual available to download no electrical layout drawings.... typical
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I'm pretty useless with electronics and correct me if I'm wrong, but if the dip i/c was the problem wouldn't it effect all the transistors if they're all linked on the drawing?
Right I was looking at the wrong side of the board told you it was a shot in the dark, have found a schematic of Frankenstein same era
Q 76 has a pre drive transistor Q85 2N5060 this is a lot smaller than a TIP 122 it may well be this, you may have to replace both as Q76 could have gone again. Failing that look at page 76 above the transistors you have 2 chips controlling the lamp drive and 2 chips controlling lamp return then the big lamp 6821 PIA chip if it has gone further I would have thought the lamp return side may be faulty. that's the whole circuit
Q 76 has a pre drive transistor Q85 2N5060 this is a lot smaller than a TIP 122 it may well be this, you may have to replace both as Q76 could have gone again. Failing that look at page 76 above the transistors you have 2 chips controlling the lamp drive and 2 chips controlling lamp return then the big lamp 6821 PIA chip if it has gone further I would have thought the lamp return side may be faulty. that's the whole circuit
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I'm no electronics expert either Darren there are many on here who are though. But hey ho. l definitely think your pre drive transistor is shot. Try that first good luck.
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Thanks for your help.
Have you got any transistors I have some spare if you require them just PM me you address and they are yours.
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Sent from my D2303 using Tapatalk
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That would be fantastic! Thank you very much.