Author Topic: Defender, no video on screen  (Read 4271 times)

rogerxy

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Defender, no video on screen
« on: June 06, 2017, 06:25:04 PM »
I bought a Defender some time ago which was a DOA.

I have recapped all cards which made the G07 monitor alive again but still nothing on the screen. (I got video on the screen when I tried with another game so I know the monitor is working)

I've done som work with the PCB:s as well:

- Changed to a switched power supply (from arcadeshop), just to get the regular PS out of the equation

- Changed the ROM Board Ribbon Cable (to the one from arcadeshop)



- Changed the 4116 RAMs to 4164, as well as the 4164 adapter from arcadeshop



- Checked all ROM:s (all are OK)




Despite this, the problem is the same as it was before I did all of the above :(

I get raster on my monitor, but it shows nothing. The 4 LEDs on the ROM board are fully lit (no blinking) from the second I start the game.



+5V, -5V and 12V all seem to be ok

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So, my question is, could anyone help me where I continue my trouble shooting. I am unfortunately stuck as of now :(

Thank you very much in advance


rogerxy

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Re: Defender, no video on screen
« Reply #1 on: June 06, 2017, 06:27:11 PM »





Ramakers

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Re: Defender, no video on screen
« Reply #2 on: June 06, 2017, 08:41:25 PM »
Have you any means of checking the signals on the boards? I think the CPU doesn't start. That's why the test LED's don't blink.
First I would check the clock signals (pg12) and the reset circuit (pg9) the manual can be found on the KLOV http://www.klov.net/manuals-videogames/D/Defender.pdf

rogerxy

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Re: Defender, no video on screen
« Reply #3 on: June 06, 2017, 09:09:42 PM »
I have a logic probe. I'm not that familiar with but I will give it a try, thank you for your advice, I will get back with my results :)

rogerxy

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Re: Defender, no video on screen
« Reply #4 on: June 06, 2017, 09:25:35 PM »
The clock generator crystal gives PULSE on one leg and LOW on the other leg, so I guess that works

Do you mean the CPU on the main board or the ROM board? I've found pulse on both of them but not sure exactly where I shall look though  :(

Ramakers

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Re: Defender, no video on screen
« Reply #5 on: June 07, 2017, 08:51:38 PM »
Has been a while since I had a defender on the bench, does it have a CPU on the ROM board?
Anyhow start with the main CPU on the main board. The MC6809 located at 2I. Here is the datasheet:
http://www.gbgmv.se/dl/doc/md09/MC6809_DataSheet.pdf

Look for activity at the address and data pins.

On the other hand, what game did you use to check the monitor?