Defender: 4 LEDs and bars

texasmame

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Well, in the multiple on/off cycles that went with fixing the monitor (completed successfully), seems the game's boardsets have developed an issue.

The sounds were always a bit wonky but I figured I'd get to that once the monitor was fixed.

The monitor is now fixed but the attached pic is happening now, along with no sound and the dreaded all 4 LED staying on solid error. The reset switch on the board does nothing as well.

After some time, I came upon this:
http://www.arcadesolution.com/rom.html

Reflowed the socket, cleaned the legs of #3 to no change.

Voltages test fine except for the 12 which gives about 10.5 but I was thinking that was what was messing the sounds up.

So. . .

1. Further suggestions?

2. Anyone local to DFW have a known working ROM board for testing? Hoping this is a ROM 3 issue and not something more in depth like a watchdog problem or whatnot.

3. Anyone want a project Defender with two working chassis? ;)

EDIT: Oh, also reflowed ribbon cable pins on both ends.
 

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If you have a logic probe, check pin 37 of the CPU. This is the !RESET line. It should be solid high. If it is pulsing, that is the watchdog reseting it. That means the adressing is messed up. About 50% of the Defenders I have seen lately that have that issue have had one or more of the 7474's go bad.

It probably isn't the ROM borad.

ken
 
Hmm. . . okay. I did get a logic probe a while ago - guess it's time to use it! :)

Are the 7474s still produced or do they have an NTE equivalent in case they need replacing?
 
They are still available. Jameco has them as do Mouser and just about everybody except RadioShack.

ken
 
i want one... just dont have funds for one...


Damn. Didn't see anything in your garage that would interest me either.

Gonna try the logic troubleshooting as suggested before I throw up my hands in disgust and put it out there for sale/trade.
 
3. Let me know if you decide to get rid of it...
 
I've got some 74LS74 chips kicking around but I take it they are not the same as the 7474?

EDIT: Hmm. . . looks safe to give them a whirl I guess??

The(7474) "Dual D Flip-Flop" Diagram:

If you would like to see under the hood of the IC, here is what it would look like. Now, some companies may change the label of the pinouts, but this is what the standard 7474 IC looks like. If you see something like 74xx74, xx being some letters like LS, HC, or whatever, that just means there is something different about the performance of the chip usually, however the function is still the same.

http://en.wikipedia.org/wiki/User:Dualdflipflop
 
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If you have a logic probe, check pin 37 of the CPU. This is the !RESET line. It should be solid high. If it is pulsing, that is the watchdog reseting it. That means the adressing is messed up. About 50% of the Defenders I have seen lately that have that issue have had one or more of the 7474's go bad.

It probably isn't the ROM borad.

ken

Okay - first foray with a logic probe!

First, I've got it set to TTL (rather than CMOS) and to PULSE (rather than MEM). It's showing to be stuck in LOW with no pulse at all with the beeper going off.

What did I win?

:D

EDIT: Replaced the 7474 with the 74LS74 as previously mentioned to no change - still stuck low.
 
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i have a cpu board of unknown working condition but is super clean and looks really nice... just wait...... 12 games will be here about 5-6ish...
 
Okay - first foray with a logic probe!

First, I've got it set to TTL (rather than CMOS) and to PULSE (rather than MEM). It's showing to be stuck in LOW with no pulse at all with the beeper going off.

What did I win?

:D

EDIT: Replaced the 7474 with the 74LS74 as previously mentioned to no change - still stuck low.

If it is stuck low, that means the !RESET line is being set continuously. About 30% of the time that means the CPU chip is toast. Try replacing the CPU chip.

Otherwise, you will need to pull the schematics and walk the reset line through a couple of gates to the last (or first, depending on your point of view) transistor in the RESET circuit. If one of the gates is stuck, that will cause that issue.

ken
 
If it is stuck low, that means the !RESET line is being set continuously. About 30% of the time that means the CPU chip is toast. Try replacing the CPU chip.

Otherwise, you will need to pull the schematics and walk the reset line through a couple of gates to the last (or first, depending on your point of view) transistor in the RESET circuit. If one of the gates is stuck, that will cause that issue.

ken


I don't have a spare 6809 around. Looks like NTE makes one but Fry's doesn't carry it, nor does Rat Shack.

I'll update with any progress. . .

Thanks for your help :)
 
You can get them from Jameco and Unicorn also. I know, not local.

Check with Trey, he should have some spare Williams boards you can "borrow" a CPU from for a couple days.

ken
 
If you have a logic probe, check pin 37 of the CPU. This is the !RESET line. It should be solid high. If it is pulsing, that is the watchdog reseting it. That means the adressing is messed up. About 50% of the Defenders I have seen lately that have that issue have had one or more of the 7474's go bad.

It probably isn't the ROM borad.

ken

will a 74HC74 work for the 7474?

I believe the hc is just High Current.
 
At the urging of Gamefixer (thx, Matt), I removed the reset pin (37) and applied 5v via a resistor (3.8k in this case). Got it to fire up to a ROM error now.

If I apply the powered resistor at prior to startup and leave on - no change, still no boot. If applied *after* startup and kept on until the ROM error pops up, that's when it will boot to the ROM error then hold there as normal.

So, it's not an issue of 5V simply not getting to the reset pin so would this be a watchdog error or something else?

EDIT: LEDs indicate 1 and 3 which would be IC10 according to the manual. Not bothering with that yet - wanna get this reset thing licked first.
 
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