Arcadenut
Well-known member
Can you post a pic of your board?
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Please post all monitor technical topics in the Technical - Videogames - Monitors section, not in the General Help section.
Dead Defender
- Thread starter jehuie
- Start date
Can you post a pic of your board?
OP
OP
Sure, I can do that in a little while. However, it's exactly the same as the one in the Defender manual here: http://www.arcade-museum.com/manuals-videogames/D/defender_2.pdf
the board layout on pages 6 & 7 looks identical to it but neither of those locations exist.
It is always hard to tell board layout with a chopped up manual. Here is a link to the hardware ID photos from Robotron-2084: http://www.robotron-2084.co.uk/techwilliamshardwareid.html#defender
This should help ID the board.
ken
This should help ID the board.
ken
OP
OP
Ah I see there is a difference. I was off at a movie (X-Men: Reboot) and didn't have a chance to take a pic of the board but it looks like this one. Which is the later board right? But now I'm confused...if this is the later board, and the Theory of Operation manual is for the later board....then why does it refer to chips 5D and 6D which don't exist on the later board?
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Arcadenut
Well-known member
Sorry, my mistake. The Theory of Operation I was looking at didn't match the board. So I made a few pic maps based on the Schematics.
The first one is just a grid showing chip locations. I hate the fact that they used a 2pt font for the grid labels. My eyes aren't that good any more
The second one should show you the chips to check.
It might be easier to start at the CPU pins 34 and 35 and work backwards since you've determined that the crystal is in fact doing something.
(someone correct me if I'm giving the wrong info please!)
So from Pin 35 of the CPU go to:
Pin 2 of 7L
Pin 5 of 7J
Pin 9 of 7J
Pin 4 of 6R
Pin 8 of 7P
Pin 12 of 7P
OP
OP
Awsome, thank you! Those markups are very helpful. I ran through the sequence and nothing was pulsing until I got to 7P so I backed up and pulled 6R. Yay, it was in a socket! I went to Fry's earlier but they don't carry 7474's so I'm on the hunt now. That place in Berkeley might have them but it's a bit of a drive. Maybe I'll just order online somewhere.
I would give you rep again but it won't let me now. Someone please do that for me!
I would give you rep again but it won't let me now. Someone please do that for me!
Arcadenut
Well-known member
You can replace it with a 74LS74 to test it and make sure that's what the issue is, then when you get a 7474 you can swap them.
OP
OP
Thanks but I don't have one of those either. Although I bet there's one in Star Wars or Tempest huh? Hmmm....
Arcadenut
Well-known member
Probably not socketed. The one in your Defender was probably replaced once before.
7474 or 74LS74 should be used on quite a few games, if you have a parts board, check on it. You will probably have to desolder it.
This won't help you find the 7474s but it may help identify parts:
It needs a lot of cleanup since I had to stich it together manually from the really bad scans in the PDF on the net. I have a Defender manual now, so when I get some time, I'll rescan it and try to put a better version together.
ken
It needs a lot of cleanup since I had to stich it together manually from the really bad scans in the PDF on the net. I have a Defender manual now, so when I get some time, I'll rescan it and try to put a better version together.
ken
Attachments
splattergatz
Well-known member
whats it ats on the chip ?
if it's low, then add a 5K Ohm pot to R2
got one from one of Bob R's monitor pot kit
it's fun to dial it in to +5.1
Attachments
OP
OP
Well I got the 7474 and was hopeful that it would fix things. Threw it in there and still doing the same thing. Which is nothing.
I'll go re-check everything with my logic probe again. Sigh.
OP
OP
Are you fairly sure these are correct? Perhaps you can point me to the diagram, flowchart or schematic that you derived this from. When I go in reverse...
Pin 12 of 7P has a pulse
Pin 8 of 7P has a pulse
Pin 4 of 6R is not pulsing....however, pin 3 is pulsing.
This is after replacing the chip.
Arcadenut
Well-known member
Sorry, after re-reading that it did seem like I was telling you the order... but it should have been "Here are the pins to check (in no particular order)."
Odd, I looked on ArcArc and didn't see the Defender Schematics. I uploaded a copy of the Schematics that I have to my site, you can download them here:
http://www.arcaderestoration.com/files/Defender Schematics.pdf
OP
OP
I'm confused but I'm also tired. I'll re-read that tomorrow and it will probably make sense. Thank you and good night!
OP
OP
Thank you for posting the schematics. That's the best looking set I've seen. You can actually read them! I'll take a closer look tonight. In the mean time....
What does it mean if pin 4 of 6R is not pulsing?
That side of 6R is in divide by two mode, so it is generating a 6MHz clock signal. I'll need to trace where that is connected because I think there is a typo in the page 2 schematics. I wasn't able to find a 6MHz feed, but if I am not mistaken that clock is used to drive either CAS or RAS (or both) and without those, the RAM will not work.
ken
ken
OP
OP
Thanks. I need some basic schematic reading help. Do you know of any online tutorials or good places to start? I mean basics. Starting with definitions of Vcc, Clk, Q, etc.
Arcadenut
Well-known member
OP
OP
Thanks. But I don't understand things like does CLK mean that's where the clock input signal is going to the chip? Or is that a signal coming out of the chip? And what if it has CLK1 and CLK2? What's the difference between CL and CK in the abbreviations. What's Q? And what's Q with a bar over it? All that stuff? Is there a general resource available for folks just starting out?
