Help - DK blue screen

[Lucky1]

Dear Jumpmen, 

First time I post on this forum. Just bought a non-working Donkey Kong. When I turn it on, the monitor shows a blue screen, like if there was no signal. (see image)

What I've done so far:

a) Checked the power supply: missing +5, +12 and +24
b) Changed IC3 (LM7812) and IC4 (LM7824) on power supply
c) Rechecked Power supply voltages = All's good now

9P connector:
1brown gnd
2red gnd
3orange gnd
4yellow +12v
5green +12v
6blue +5v
7purple +5v
8gray -5v
9white +24v

10P connector:
1brown -5v
2red -5v
3orange -5v
4yellow -5v
5green gnd
6blue gnd
7purple gnd
8gray gnd
9white +5v
10black +5v


d) checked the voltage on the PCB at the unused edge connector = +5 and + 12 ok

e) Unplugged and plugged the connectors and the inter board connectors

f) Pushed on all roms and processor

g) checked the sync/rgb cable

I did not reseat the ICs because most of them have rusty legs and they will break if I attempt to do this.


If the board has power, shouldn't there be at least something showing up on screen?


Thanks

[homerwannabee]

Holy cow!  Donkey Kong is the originator of the Blue Screen of Death! 

[Lucky1]

Looks like a monitor Issues, neck board probably. Missing red and green.

[Sock Master]

Even if the CPU is not running and/or there are no/bad program ROMs, you should see something on the screen - random characters like this:


Also when you power it up, it should make a sound like the jump sound - also even if the CPU isn't running.

To check if the CPU is running even with no image, try inserting a coin and pressing start to check if it plays the sounds of gameplay.

Looks like monitor issues but it could be other issues in addition to that.   The monitor probably needs a cap job if it looks like it's not filling the viewing area uniformly and/or the beam is out of focus.

There are adjustments in the back of the monitor.  You might be able to adjust the red/green/blue levels and see if there's some sort of image.  Also on the monitor's flyback (big plastic thing with two plastic screw/adjustments) there are two adjustments for 'focus' and 'intensity?'... that might help focus the beam and turn down the blue.  But if the capacitors are bad it's probably not able to be compensated for - and there are high voltages there.. and if the flyback transformer is going it might also start making buzzing noises and emitting blue sparks.   It can be replaced if that happens, but seeing little lightning bolts coming off of it might be a little intimidating, also very zappy.

[YesAffinity]

This stands out to me, as being your biggest potential issue.

"I did not reseat the ICs because most of them have rusty legs and they will break if I attempt to do this."

There's probably socketed chips that are not making good contact, but as SM mentioned, that's possibly not your only issue.  Nintendo screens will display all white if the cab and the monitor have power but no game video.  You likely have an improperly-white-balanced screen, which is why it appears blue.  But, the monitor is at least powering on..

[VeryApe121]

Listen to this guy.

Even if the CPU is not running and/or there are no/bad program ROMs, you should see something on the screen - random characters like this:


Also when you power it up, it should make a sound like the jump sound - also even if the CPU isn't running.

To check if the CPU is running even with no image, try inserting a coin and pressing start to check if it plays the sounds of gameplay.

Looks like monitor issues but it could be other issues in addition to that.   The monitor probably needs a cap job if it looks like it's not filling the viewing area uniformly and/or the beam is out of focus.

There are adjustments in the back of the monitor.  You might be able to adjust the red/green/blue levels and see if there's some sort of image.  Also on the monitor's flyback (big plastic thing with two plastic screw/adjustments) there are two adjustments for 'focus' and 'intensity?'... that might help focus the beam and turn down the blue.  But if the capacitors are bad it's probably not able to be compensated for - and there are high voltages there.. and if the flyback transformer is going it might also start making buzzing noises and emitting blue sparks.   It can be replaced if that happens, but seeing little lightning bolts coming off of it might be a little intimidating, also very zappy.