Defender growls no more...

Sirius

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A brief history... the machine was only supposed to need a power supply. When I plugged it in there was only 2 of 3 led's lit (no -5) on the power supply. After some point the -5 came back on and the the machine did it's growl and the screen was scrambled. After a few adjustments to the monitor and several restarts the screen was working properly. I finally got it to show either a ram or rom error, not sure which, it was late. I was able to get past that to "game over". I coined up the machine and played 3 games, after that it was all down hill! The screen went corrupt...kinda looked like "Klingon". Now only 3 led's light on the rom board, don't blink and stay lit. I cant say that I saw the 4th led ever light. Anyway, now there "was" no video and no growl...sigh!!! I got life back in the monitor after swapping the 2 7474's, but still no growl.

Come to find out there was a bad connection on the -5 fuse holder. I've since cleaned it and re flowed the solder connections on the power supply. Tested the power in numerous spots (connectors and ram). Only suspect voltage was the 6.3vac. It's reading at about 4.5 & 5.5. I've replaced all the ram with new 4116's and re-flowed all the connectors on both the cpu/video and rom board. I've also re-seated every socket chip on the board, and replaced the 40 pin ribbon cable, but still no growl.

With the 7474's in their original sockets the mpu reset (pin 37) did not work. When I swapped the 7474's pin 37 behaves normally. With the logic probe on reset pin 37, I read a hi/lo pulse that goes low (1 sec) when the reset button is pushed. Still the reset does nothing, led's don't blink.

Can anyone decipher these values?

Pin 2 of 7L = hi/lo/pulse
Pin 5 of 7J = hi/lo pulse
Pin 9 of 7J = hi
Pin 4 of 6R = hi
Pin 8 of 7P = lo/pulse
Pin 12 of 7P = lo/pulse

...so any help would be greatly appreciated.
 
Nope...no rug pattern and I've got that pdf. There is no reference to the first 3 led's. As soon as power is applied they come on and stay on. They don't blink what so ever.

Power Supply Voltages

@ PCB Header
+5 =4.97
+5 =4.99
+5 =4.99
+12 unr = 12.48
+12 unr = 12.51
-12 unr = 14.52
+12 = 11.97
-5 = 4.82

@ Coin door

-6.3 = 4.0
-6.3 = 5.2
+27 = 30.2

@ RAM - readings taken from location 1Z, upper right on board.
Pin 1 = -4.85
Pin 8 = +11.81
Pin 9 = +4.91

I ordered some new 7474's and sockets, I'm also planning to rebuild the power supply.

Is there a method of checking the CMOS? If I'm not mistaken the CMOS is a programed chip? Or could it be replaced?
 
If they are not blinking, then the CPU is not starting the code. Watch pin 32 of the CPU. This is the Read/Write enable line. It should go Low (IIRC) when the reset button is pressed and then start blinking like crazy. If it does not, you probably have a condition where the RAM is in read mode and the ROM is swapped out.

On Williams boards the some of the RAM and all of the ROM are mapped to the same memory address space. In normal operation, a read into this memory space returns the ROM data and writes go to the RAM memory. But during the POST the memory is set to read and write to do the memory test. If the memory addressing is off by just an instant, the CPU tries to execute the garbage from the rug test.

Finding what is off in the circuit is always a lot of fun.

ken
 
Okay, I tested pin 32 of the CPU. It's high and pulsing like crazy. When I press reset, it just stops pulsing and stays high. Restarts pulsing like crazy after about 1 second.
 
Here's something to ponder...I mentioned that the 4th led is not on. I've never seen it light up. I tested the power on the first 3 led's and got +1.60. When I tested the 4th non lit up led, I get a reading of -2.81, huh?
 
I was following the CPU flow chart when I came to that. I got stuck at that point because it says "5P Pulsing in CRT". I checked Chip 5P pin 6. It's high.
 
I was following the CPU flow chart when I came to that. I got stuck at that point because it says "5P Pulsing in CRT". I checked Chip 5P pin 6. It's high.

What is chip 5p and I can look it up in the data sheets to tell ya where/what to look 4. I think I have downloaded the manual for that borad set.

you are using a logic probe right?
 
Okay, I tested pin 32 of the CPU. It's high and pulsing like crazy. When I press reset, it just stops pulsing and stays high. Restarts pulsing like crazy after about 1 second.

That is the watchdog circuit. It means that the CPU is not running. Unfortunately, that means that there may be one or more of a long laundry list of things that have gone south.

(1) the CPU chip may be bad
(2) the ribbon cable to the ROM may need to be recrimped or replaced
(3) there are one or more bad RAM chips messing up the data lines or address liines
(4) the CMOS chip may be bad and it is messing with the address/data lines
(5) one of the clock outputs is not clean
(6) one or more of the 7474 chips has gone bad
(7) one or more of the data buffer chips has gone bad
(8) one of the chips that decode the address for the watchdog has gone bad
(9) the connector on the MPU board for the ROM ribbon cable is bad
(10) an addressing chip on the ROM card has gone bad

Or it could be something else. The above list is just the things that I have found and fixed on boards over the last month. There seem to be a never ending list of things going bad.

ken
 
What is chip 5p and I can look it up in the data sheets to tell ya where/what to look 4. I think I have downloaded the manual for that borad set.

you are using a logic probe right?


Yep, using a logic probe. The number on the chip is "7432N" (8107).
 
That is the watchdog circuit. It means that the CPU is not running. Unfortunately, that means that there may be one or more of a long laundry list of things that have gone south.

(1) the CPU chip may be bad
(2) the ribbon cable to the ROM may need to be recrimped or replaced
(3) there are one or more bad RAM chips messing up the data lines or address liines
(4) the CMOS chip may be bad and it is messing with the address/data lines
(5) one of the clock outputs is not clean
(6) one or more of the 7474 chips has gone bad
(7) one or more of the data buffer chips has gone bad
(8) one of the chips that decode the address for the watchdog has gone bad
(9) the connector on the MPU board for the ROM ribbon cable is bad
(10) an addressing chip on the ROM card has gone bad

Or it could be something else. The above list is just the things that I have found and fixed on boards over the last month. There seem to be a never ending list of things going bad.

ken

Did you hear that big heavy sighhhhhhhhh? Well... the 7474's and sockets I ordered should be here on Friday. I'll start there. I also borrowed an Oscilloscope from a buddy at work. It's an oldie, probably older than Defender. Looks like it came from a mad scientist lab! Now I got another thing to learn...google here I come! Actually I've got some arcade repair videos and I think one of the topics was learning to use an oscilloscope, still may be over my head. As far as the cpu goes...I suppose it could be bad, even with life on all the pins? I found one on Ebay for $15. Pacmandotcom has a similar cpu (http://www.pacmandotcom.com/processors-40-pin-ics/595-6809-mpu.html) for $5.75, but...it's not an exact replacement. If you open the link you'll see that the numbers on the chip are different. I emailed him and asked if it would work on the Defender board and he said "yes". It's just faster. The ram and clock is what makes me doubt it's compatibility.
 
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If it is a 68B09E then you are good. The E means that it uses an external clock. The 6809 and 68B09 chips (no E in the designator) use an internal clock and it will almost never be synched with the clock on the board, so is useless.

The B just indicates that it will clock to 2 MHz. Williams games run at 1 MHz. SO you are good.

ken
 
If it is a 68B09E then you are good. The E means that it uses an external clock. The 6809 and 68B09 chips (no E in the designator) use an internal clock and it will almost never be synched with the clock on the board, so is useless.

The B just indicates that it will clock to 2 MHz. Williams games run at 1 MHz. SO you are good.

ken

It's the MC68BO9EP and says in the description..."6809 8-Bit MPU with ram and clock 40 Pin DIP Package".
 
Progress?

Okay...the growl is back! Still not there yet though. I re-did the ribbon cable between the rom board and cpu. Apparently I didn't clamp it hard enough the first time. I replaced the 2 socketed 7474's and also the one at 7L. I tested the reset pin on the CPU and it's high and when I press the reset it goes low for 1 second (correct?).

So what I see on the display is vertical color bars and it appears to be running the rug test over and over. Also I should note that the 7474's I oredered have the following designation on them...7474AN. Are these compatible? They were stated as 7474n at Jameco's website.

3 of 4 led's light and then go out (1,2,3). I'm telling ya, that 4th led never lights. If I press reset, the 3 led's light and stay on. Question, is it supposed to growl if you press reset?
 
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