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I know Bob it’s driving us both bonkers! the chips are HFC branded? But I did fit a pull first and it passed a vector test on my programmer I bought 10 new ones I will test them also and will take a pic of the waveform going into pin13 thanks Ronnie

Hello everyone, I'm sorry to be stuck in this thread. I recently registered. I can log in. But, I can't read the threads. I get an error message every time. >>> Sorry, there is a problem Something went wrong. Please try again.<<< I sent a message to the webmaster and Pete, but no response. If anyone could help me, that would be great. I'm giving an email, because I don't know if I can read my messages through the website. lamiral29@free.fr Thank you very much @+ Sorry for my poor language.

Of course it is 14 pin, I'm losing my marbles I think. I wouldn't be to concerned about the difference of the continuity and Ohms reading as there's enough voltage/current to operate a junction of a semiconductor on the continuity setting. I think the main enigma is the waveform goes into 13 and doesn't come out on 12??? and there's no short on it (as you had the pin removed anyway). It was a bona fide chip you replaced it with? You can see I'm clutching at straws now!

Hi Bob, sorry ic18 is a 14 dip chip so pins 14 and 7 are vcc and I get a good 5 v pin12 to ground now this is strange! On continuity I get 600 ohms but in ohms check I get 4k ohms? Not sure how that can be? pin12 to pin28 of the 6840 has continuity hope I’m not doing something daft again!

Blimey Ronnie this is turning into a real poser??? Without the chip in (IC18) is the power and ground good to pins 16 and 8 ie don't use any other ground. Next what does the resistance measure from pin 12 to ground? Also check the via isn't broken on pin 12 ie make sure there's connectivity from pin 12 to the 6840 pin 28. I'm sure that will be OK but might as well confirm. Lastly can you post a pic of that area with chip in. There's got to be an obvious answer to this but I'm scratching my head at present.

Can’t find any issues with the socket or the traces from it, even if I leave pin12 out the socket I still don’t see the signal on the pin on this board the trace on pin 13 looked slightly shallower than on the working board but was still near 100hz

Lol yeah that stumped me I was checking vcc arse for tit! But once I realised vcc is fine as is ground And I see what you describe on a working board, so god knows what's happeng here?

Please forgive me for mentioning this but pin 1 is top right hand as you look at the board.

I know it's a bummer! Vcc is fine on the chip too, I must be missing something, going away to compare to a working board

Don't understand that Ronnie? If the 100Hz is going in it should come out as a nice 100Hz square wave about 5v p2p assuming the chip is powered ok. Pin 12 feeds IC2 (6840) and IC3 (6821) but I can't believe they would be causing anything.

Ark Aid Repairs is repairing it.

Thanks appreciated

Got the new chips today so pin12 still the same! Pin13 is like this does that look right? Sometimes it will come up with 50pm loked alarm on the alpha when I’m probing ? thanks Ronnie

Great work again bob and there's no end to the 3d printing capabilities. The mpu3 boards seem somewhat wrong without the cart surround protector so a very worthy project .

Nice to see an admc machine crop up .has to be worth £60 just for the parts

I have a few 80s mpu4 game cards... I'll.check and let u know tomorrow ..

It's a tantalum capacitor so there's a good chance it has! Snip it off and try it again.

They shouldn't run hot, sounds like a chip has failed unless C1 has gone short?

Will try thanks. The board got really hot after being plugged in for a few seconds.

or take the roms out one at a time and clean the pins but make sure thay go back in the right way

check in that white socket for bent pins

Unbelievable 😂👍.great capture

Cabaret 144 jackpot😂😂😂

My last visit was great. I did a tour video to update you all.

Ah ok thanks