defender sound board weirdness

the one in defender is squarish...time warp is a rectangle. ive got quite a few extra DIP sockets, mostly robbed from a galaga board i worked on. while those sockets seemed ok, i still replaced them with some fancy "machined" sockets. they DO seem very nice. unfortunately, i dont have a 24 pin in these, just the 40 pin. so im only halfway there, if i were to decide DIP sockets is the problem, but i really dont think it is. a crap socket would be an intermittent connection, and this error occurs at exactly the same time, every time. its far more consistent than and intermittent or a non-connection would be, i think.

im sending the sound board back to austin, this'll be the third trip down there for this project. the tech has been very reasonable on prices and turnaround, but maybe if we could test things longer than 2:32, you know, that might be better?
 
bad 6810 SRAM chip
The 6810 is a common issue and can cause some strange sounds, or intermittent problems.

'Two Birds - One Stone'... The 6808 CPU relies on the external 6810 SRAM, but the engineers at Williams were smart. The 6802 CPU has the SRAM built-in (internally) with the same addressing as the 6810. There is a pin on the 6802(36 - RE/RAM Enable) that tells the CPU to use internal, or external memory (set high to enable - low to disable). *I'm guessing at the time of their initial design, the 6802 wasn't available, or the cost was less to go with the external RAM.

HERE is the guide Dave Langley put together on his site (awesome work!).

Many times, you can just leave the 6810 in place on the board and use the 6802 CPU RAM without issue, but I've had a few instances where an address line was 'Stuck' and I had to remove the 6810 completely to get the board running 100%

~Brad
 
Using a 6802 isn't a bad option if the CPU chip is also bad. The 6802 seems like it is easier to come these days than the 6808 chips.
 
Using a 6802 isn't a bad option if the CPU chip is also bad. The 6802 seems like it is easier to come these days than the 6808 chips.
you can run the 6802 as is or there's a mod to disable reaching out to the 6810 and using internal 6802 ram. you'll see a lot of this forward thinking trickery on Williams pinball also lol
 
i am liking this idea...

so the idea here is procure a 6802 and do the jumper mod so it pulls its ram internally... skipping the presumed faulty 6810 entirely? i have a 6808 in there now... it is socketed... so just go grab a 6802 and follow the instructions for cutting the trace and whatnot? sounds easy enough...
 
cutting the trace and whatnot? sounds easy enough...
Yes, and if you still have issues, you can also try removing (cutting or desoldering) the 6810 out of circuit completely. That will either fix the problem, or eliminate a big chunk of possible errors.

~Brad
 
im sure its an equivalent, but my 6810 isnt a 6810....looks to be a motorola chip marked 5A-9003 and then 8114 under that.

this board had been serviced by an unknown tech back in 2006 or 2009, and theres a little red dot from a paint marker on that chip, indicating (i believe) that it had been replaced.

im hoping this changes nothing about the 6802 swap. i really like that forward-thinking from williams. such elegance in its design, how cool is that!?
 
That's just the Williams Part Number for the 6810 - They had a bunch of parts custom labeled such as the Bottlecap (T0-3) power Transistors on the heat sink.

~Brad
 
quick update....
i ordered my replacement 6802 from frickin china. im not sure how i missed that highly important detail. anyhow, it should be here sometime mid-month. i could probably order a new one from anywhere else and it'd get here first, but its fine. plenty of other things to do around here...

happy new year everyone!
 
Lots of counterfeit/bad/wrong parts coming out of China - fingers crossed you get a good one!

~Brad
 
Lots of counterfeit/bad/wrong parts coming out of China - fingers crossed you get a good one!

~Brad
my exact thoughts

I bought mine from Twisty Wrist Arcade. I'm uncertain why that store was kind of forgotten.
 
*the picture looks great*

man im such a dummy for this one. its in new jersey i guess, so probably another day or two and we'll find out.

twisty wrist is a great store! ive used them quite a lot before. sounds like ive got a 50/50 on using them again soon! bah, i guess thats just the price of being young and dumb. except im not really that young anymore, so mathematically...
 
got my chip in today!

the sound still works after the modification, so thats good, but it still dies after 2:30. i actually didnt time it, and it did seem like it lasted a little longer than 2:30, but it couldnt have been 4 minutes. SO....back to austin it goes, i guess... (unless anyone has any other tricks i might try.)
 
Did you cut the trace to enable the internal RAM on the 6802? I'd remove the 6810 too (since it's not needed anymore and could still be causing an issue) - (Can just snip the legs with some small flush cutters in lieu of desoldering).

~Brad
 
i did cut the trace and tested it, no continuity was observed.

i did not remove the 6810. certainly, it shouldnt hurt to do so at this point, however: the gentleman i sent these defender boards to be repaired has informed me that he will either fix this sound board, or give me a known good one out of his spares, so that is probably what im going to do. i love a challenge, but ive been working on this machine for a friend of mine since summer....probably about time i get it back to him!
 
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