Defender project revisited

[scottz29]

well, as a continuation of the same issue I had last year, I still have a Defender that plays the wrong sounds during gameplay.

This sounds like a bad PIA to me. I had the same problem in my Robotron. Cycling through the sound test showed one channel was dead which resulted in very strange/missing sounds during gameplay. Logic probe confirmed the appropriate pin on the PIA was not firing.

During debugging, I remember wanting a video of the sound test screen when doing this too, so once I got it fixed, I *think* I shot video of the whole process I used to debug & fix the problem, but...of course I never got it online... I'll look for it eventually.

Swap out that PIA and report back.

 

[YellowDog]

ok, new updates. so upon inspecting things, I was getting ready to test voltages when I realized the switcher that was transplanted into my machine DOES NOT output -12V. whether that makes a huge difference or not, I don't know, I would imagine so if that's one of the voltage requirements right?

at any rate, I started rebuilding the Defender PS board I had, for all those that swear by cleaning PCBs with simple green and a hose, I commend you, because the board looks like new now.

as I'm doing this I got to wondering what the hell the 3rd connector on the board was for and wondering how you get AC to it, and uh... yeah, that was in fact lopped off in my cab. I have all the necessary molex parts to rebuild a new connector, except I don't know where all the wires hook up to the transformer, as the wires were all cut off.

the wiring diagram I have calls for some "green" wire too, which I saw coming off the line filter, I'm not sure if that has anything to do with it too but I found several lugs on the transformer that have soldered wires and I don't know what colors are what.

if there's anything else I need to know about for redoing this 4J1 connector, please let me know.

also, I wiggled the ROM board -> sound board harness while the game was running and got it to play entirely different sounds. I'm inclined to believe that's correct, I don't think there's anything wrong with that harness because all the continuities checked out (I'm guesstimating). I also followed one of those flowcharts where you unplug that connector entirely to see if the game still plays sounds and it didn't (which is a symptom of a bad ROM board I guess?)

EDIT: Translation: primary main objective = finding out where the 4J1 wires hook up on the transformer. need a diagram of what colored wires go where on the transformer to get power to this board. I also broke the -5 LED off like a dickhead, these are diodes though, does that mean I have to throw a new LED in there?

If the switcher does not output -12V it is still ok, as long as the -5V is attached to the -12V inputs on the sound board. The sound will not be as loud as the -12V is used to drive the output of the amp.

The Defender drawing set has the wiring harness diagram which will show how the transformer is wired up.

From the transformer secondary to the power supply board:

[FONT=Courier New]Transf - wire color - PS board[/FONT]
[FONT=Courier New]15     GRY-GRN       3 (11.3VAC)[/FONT]
[FONT=Courier New]16     GRN           5 (NEUTRAL)[/FONT]
[FONT=Courier New]17     BLK           1 (11.3VAC)[/FONT]
 
[FONT=Courier New]11     GRY-YEL       8 (20VAC)[/FONT]
[FONT=Courier New]12     GRY-WHT       9 (NEUTRAL)[/FONT]
 
[FONT=Courier New]13     VIO-YEL       11 (11.5VAC)[/FONT]
[FONT=Courier New]14     ORN           12 (NEUTRAL)[/FONT]

The 6 Pin connector on the power supply board is for the coin door:
Pin 1 = 6.3VAC Return
Pin 2 = 6.3VAC for coin door bulbs
Pin 3 = +27VDC for coin lockout solenoids
Pin 4 = NC
Pin 5 = NC
Pin 6 = Ground (Diagram lists it as "To Memory Protect Interlock" )

The Power input connector on the sound board:
Pin 1 - NC
Pin 2 = +12VDC Unregulated
Pin 3 = +5VDC Regulated
Pin 4 = NC
Pin 5 = Ground
Pin 6 = NC
Pin 8 = -12VDC Unregulated
Pin 9 = NC

The LED is not important for operation of the board, but you can get a standard LED from practically anywhere (even RadioShack) and plug it in. Just remember it is going to a negative voltage so it is backwards compared to the other 2 LEDs (which go to positive voltages).

ken

 

[mecha]

are the lugs labeled on the transformer? (the numbers)

a picture of a transformer with the wires coming off it would be wonderful lol

 

[scottz29]

Hate to be Captain Obvious, but did you check for cold solder & reflow solder on all the header pins on all your boards? I didn't see this in any of the posts...sorry if I missed it.

 

[mecha]

power supply board is in, game runs fine, same sound issues.

I'll try swapping the PIA tomorrow.

 

[scottz29]

Don't forget to check your header pins for cold solder with a loupe. I also see you mentioned:

also, I wiggled the ROM board -> sound board harness while the game was running and got it to play entirely different sounds.

To me, this can only mean one thing - broken/cracked/cold solder on your header pins. It might be a combination of both that and the PIA, but reflowing solder is free, and much easier than desoldering and replacing that 40-pin PIA chip.

 

[mecha]

I reflowed all of those actually, just isn't it a combination of those pins hitting that generates different sounds? I'm talking I was pulling the whole connector side to side (like on and off, it's easy to do with my new connectors), not like a grabbing the header and going up and down with it lol I also straightened all the pins too.

those pins are kinda shitty to work on, solder goes around them, not all over them. if I had more header parts I would've just replaced them. so I'm leaning towards it being a bad PIA.

it's safe to assume that all the other circuitry works fine, yeah? I've swapped CPUs between the boards like 18 times now, I don't think that's the problem. I forgot I also have to make my own test panel. and dig up another LED for the -5, but that's just cosmetic I guess. lol

how do you figure out polarity on those? I never paid much attention to that one.

 

[scottz29]

Yea, LED is not critical, but most of the time the anode (+) is the long lead. Often times on round LEDs, the cathode (-) side has a flat side near the base.

 

[mecha]

Yea, LED is not critical, but most of the time the anode (+) is the long lead. Often times on round LEDs, the cathode (-) side has a flat side near the base.

yeah, funniest thing was I took the whole power assembly out to clean the transformer and everything else, I even repainted the wood, I plug it in and uh, nothing. it was then I realized I have to have it plugged in cause it's looking for a power switch. lol

it was amazing when I plugged it all in, it worked on the first try and didn't blow anything up. it looks like mine was modified to have a pot on the +5 line, is that normal or is that something someone added in?

 

[YellowDog]

The pot on the +5V line is a common, but dangerous modification. The pots are not as stable as the equivalent resistor and can cause the voltage to drift over time. They can also get bumped and reset the voltages. This is especially dangerous with the original Defender PS boards as they don't have the overvoltage protection circuit of the late Stargate/Joust/Robotron PS boards.

ken

 

[mecha]

I tried pulling the PIA out after desoldering and broke it in half. guess there was too much on the top still lol

I'm just gonna order Bob's sound board kit and be done with it. if that doesn't get it, I'm gonna punt on it.

 

[mecha]

thought I'd share a picture of my cleaned and rebuilt power supply board. too bad I'll never get around to doing this on any of the other boards cause I don't wanna mess the sockets up. :/

note the adjustment pot on the +5, anyone know what resistor rating belongs there to "hardwire" it if you will, since I'm sure all the voltages will be perfectly fine since rebuilding it.

 

[scottz29]

Bob's kit is only caps...which isn't your problem. So you're going to order a PIA too, no?

 

[YellowDog]

And don't forget a socket for the PIA. It will save you from breaking more PIAs in the future.

ken

 

[mecha]

Bob's kit is only caps...which isn't your problem. So you're going to order a PIA too, no?

really? his kit has all the parts labeled, like the amp, PIA, CPU whatever. crystal was a separate part.

also he's got that service switch assembly thing, I don't have the bracket for it, but will that at least be the switches I need for the service panel?

 

[scottz29]

Oops, my bad! At first glance, it looked like only a capkit. Sounds like that kit should do the trick.

 

[mecha]

price is kind of confusing though. he wants $7 for the "cap kit" and the 6821 alone is listed for like $6, so I don't know, maybe you're right and he just IDed all the components instead.

 

[mecha]

it's been awhile again! but I finally got to cracking on my Defender again.

I wasn't entirely sure if my old rom board worked or not, so I swapped all the roms over and the game booted up for me. however, the same issue with "wrong sounds" persisted.

for the first time I got the meter out. all the voltages are healthy. my +5 is 5.25 at the headers, which is kinda high I think, but I don't know what this game's power needs are. to remind everyone, someone installed a variable resistor on the +5 line on my power supply board, so I can probably adjust it down.

I went over a lot of stuff on the sound board, one of those little triacs transistors didn't have solder on the top, so I added that. none of the solder work resulted in any change. I pulled the rom and sound boards and left them hooked together and metered between them at components before the headers, continuity all checked out.

since I'm getting the same thing with both rom boards, I think I can deduce that it's got anything to do with the sound signals coming off the rom board. and it shouldn't be a mismatch between the chips, because it does this with both rom boards.

I think it's logical to deduce that it's probably something with the PIA chip on the sound board right? I'll order two, I'll fix both sound boards eventually. money's tight, can't drop a bunch of cash on Bob Roberts right now heh.

I know now for sure that the rom and input boards from both boardsets I own work, if I happen to fix both sound boards, wonderful. but can anyone tell me why the old CPU board was completely unresponsive? I think I had a solid red screen on it if I recall. it's got nothing to do with ribbon cables since both rom boards work with the 2nd CPU board. if it's stuck in a reset loop, how do you fix that?

also, for the very last time, I don't own a logic probe, and I can't pull one out of my rear.

thank you.

 

[mecha]

anyone? at all? it's Defender. you love Defender.

 

[LeChuck]

I can't really tell from the previous posts, but does pressing the diagnostic switch on the sound board work (it should repeatedly play the startup sound)? If not, then I wouldn't bother looking further than the sound board until that is fixed. That should confirm basic functionality of the sound CPU, sound ROM, PIA, DAC, amp, and speakers.

There are also 6 - 7 test points on the ROM board right next to the sound board connector. They should all be pulled high (5V) initially; grounding those manually should generate the sound effects just as if the CPU had asserted the ROM board PIA lines (note that they may not all be used on Defender). I like to do this since it can verify the connectors, harness, and sound board PIA functionality in one fell swoop.

Did you ever get a replacement crystal installed? Just checking, that is most definitely a prerequisite to any other debug on the board.

BTW - You can use your o'scope for anything that a logic probe would be doing (you just have to turn your head to keep looking at the output .. so slightly less convenient for quick checks). If you don't know how to use it, it's definitely worth the time. At a minimum just be able to check for high/low logic levels, and see if a signal is toggling.

LeChuck