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PacMania - music, but no sounds

I did not! Is that a very specific chip, or just search for 74LS04 ?

Matt
 
Run of the mill TTL logic. It's still being made!
 
Ok - I pulled out P4 - and noticed 1 trace that I need to try to get back onto pin 12 (the long one at the top of the picture) but there is a trace that is loose underneath the chip also (right by the S) - that I am not entirely sure where it came from - its coming from pin 11.

Edit:

It looks like I can repair by doing a small wire from P4, pin 12 to the RAM chip - U3, pin 22.
P4, pin 11 looks like it hooks up up to SNA14 - which is pin 22 on the Sound CPU - so I could also run a wire to repair this as well?

I am somewhat hopeful this was the issue - as I knew SNA14 was not acting right.
 

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A better picture - I can see it better now - it looks like the trace that connects TO pin 11 from the via just above N4 is broken - not sure if I did that by removing the chip or not, but it seems as if that needs to be wired back up.

Once i get confirmation from the geniuses here - I will try and do this - never done any sort of trace repair work - not sure if I have the equipment for it.
 

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You can run a small patch wire on the underside of the board to reconnect the damaged trace.

Protip for avoiding trace damage going forward: after removing solder from each joint and via on the bottom, I heat the pins on the top side with a hot air station before trying to lift the chip. That‘ll help ensure that any leftover solder topside won’t grip the pin and cause a trace to to lift. If you don’t have a hot air station, you can pick one up an inexpensive one for around $35 on Amazon.
https://www.amazon.com/YaeCCC-Stati...YK2T/ref=dp_prsubs_1?pd_rd_i=B0878GYK2T&psc=1
 
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@ShootTheCore good tip. I totally destroyed a Mega CD unit by removing the BIOS chip and lifting it up ripping the vias to shreds.
 
Well - I put in a new chip - its marked as a SN74LS04N - compared to the 74LS04P that was in there - does the P vs the N make a difference? I know it does on transistors.

I was able to get the via soldered onto pin 12 - so continuity to RAM U3, pin 22 is good.

I ran a wire on the back that connects pin 11 to the sound CPU on pin 22 - and I have continuity there.

BUT - when I boot up the board, I get video sync, and then nothing.

So - either the chip I put in is wrong, or I messed something else up :( Just in case that N vs P matters - I ordered the exact M74LS04P that was in there (except the number on top doesn't match). I should get it in a few days.
 

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mathewbeall said:
Well - I put in a new chip - its marked as a SN74LS04N - compared to the 74LS04P that was in there - does the P vs the N make a difference? I know it does on transistors.

I was able to get the via soldered onto pin 12 - so continuity to RAM U3, pin 22 is good.

I ran a wire on the back that connects pin 11 to the sound CPU on pin 22 - and I have continuity there.

BUT - when I boot up the board, I get video sync, and then nothing.

So - either the chip I put in is wrong, or I messed something else up :( Just in case that N vs P matters - I ordered the exact M74LS04P that was in there (except the number on top doesn't match). I should get it in a few days.
Click to expand...
I’m still hoping that you get to fix it! I believe in you!
 
@mathewbeall the chip is fine. As long as it's a 74LS04 any extra suffix or prefix won't matter. I've checked the photos and I'm more worried that you broke a couple of traces besides the obvious ones.
There's a couple of traces that run top to bottom and are hidden by the silkscreen with the LS04's outline, right below the P4 text. Check the continuity of those traces and patch as needed.
 
ic3b4ll said:
@mathewbeall the chip is fine. As long as it's a 74LS04 any extra suffix or prefix won't matter. I've checked the photos and I'm more worried that you broke a couple of traces besides the obvious ones.
There's a couple of traces that run top to bottom and are hidden by the silkscreen with the LS04's outline, right below the P4 text. Check the continuity of those traces and patch as needed.
Click to expand...

I see what you are talking about - I will have to figure out where that was going, and check continuity.
 
Ok - so it looks like i damaged these 2 traces on the left (I will DEFINETLY be using the hot air method from now on to remove chips!)

1620950547827.png


Of the two lines - the one on the outside - goes from chip L3-pin 16 (the trace goes under N3) to S3-pin 6 (via the via) - I repaired that.

The other line - the inside line - I can't quite figure out where it goes. It seems to end under N4 - and there are no via's there. It goes to what I think is a via up under S4 (the top chip). I will have to poke around more with my continuity meter on my good board to see if i can figure out how it connects.



1620950344983.png
 
Where did you buy that YM2151 chip from the '2151' digits are wonky in comparison and font is washed out suggesting it is a fake so apart from the track issues you're experiencing now this was still part of of your original sound issues

**EDIT** Just found this page about the subject different Yamaha chip but markings similar

https://www.aidanlawrence.com/the-fake-ym2612-mystery-game/
 
Funhouse1971 said:
Where did you buy that YM2151 chip from the '2151' digits are wonky in comparison and font is washed out suggesting it is a fake so apart from the track issues you're experiencing now this was still part of of your original sound issues

**EDIT** Just found this page about the subject different Yamaha chip but markings similar

https://www.aidanlawrence.com/the-fake-ym2612-mystery-game/
Click to expand...

Interesting! I did buy it on ebay - since it wasn't working correctly, I put the old chip back in.

What i am hearing is that maybe I should try to source another one of these after i get the board back up and to its booting state.

Matt
 
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