(Topic ID: 207281)

Lethal Weapon 3 LW3 won't boot with CN5 (DMD) plugged in!

By edwood

4 years ago



Topic Stats

  • 7 posts
  • 4 Pinsiders participating
  • Latest reply 3 years ago by arolden
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#1 4 years ago

I recently had to repair a Power Supply on LW3, and basically rebuilt the entire DMD section... All zeners, transistors, and even a few resistors that seemed out of spec, etc... Once installed, I added different connectors one at a time and continued to power on the game, EVERY step worked until the last one which was adding CN5, the connection to the DMD.

Now turning on the game, the GI lights come on, and then nothing... game is basically frozen...
When I keep CN5 unplugged, it boots and plays perfectly. Just no display of course.

Checking the voltages at CN5, the +5 and +12 are good, but the voltages for the DMD are way off, like +10, -10, I think a zero even or something else small...

My question is, COULD this be the C10 and C11 caps? Probably 2 of the only things I didn't replace when I think about it... but would that be enough to make the voltages that weird AND my bigger question: Why would that prevent the game from BOOTING? Wouldn't it still boot but just have a blank display?

If anyone has come across something like this, or has an idea of what would prevent the game from booting once the display is connected, any input would be welcome... !!

Thanks in advance!

2 weeks later
#2 3 years ago

Nice little update since so many people are interested:
Plugged it in again with all connectors except CN5 and this time R10 and R11 literally caught fire.
Was quite the sight to see... I'm sure other components in the DMD section got damaged as well, so will again be replacing a bunch of components all over again...
Any idea why they would specifically burst into FLAMES vs just 'pop' or not work??

#3 3 years ago
Quoted from edwood:

rebuilt the entire DMD section... All zeners, transistors, and even a few resistors

Quoted from edwood:

this time R10 and R11 literally caught fire.

R10 + R11 are 330K 1/2W and can easy withstand 400 Volt (400 Volt² / 330000 Ω= 0.48 Watt) so my 1st guess would be that the resistors are replaced with wrong values ?!

#4 3 years ago

You got that right, they gave me 330 OHM! Just double checked the packet they were in!

probably likely I'll have to replace a ton of other parts now too

2 months later
#5 3 years ago

So an update, and some help would be LOVELY if anyone can understand what's needed next:
Rebuilt the entire DMD section again... New diodes, and zeners, resistors (ceramics still measured good), all transistors...
Now the voltages are:
66v (instead of 68v)
-110v
-88v (!!?!)

These are voltages AT the pins, DMD unplugged. 12V and 5V still reading good.

So how do I get those extra 10 volts?? Like I wouldn't know exactly which component would be the "likely culprit"...

I would THINK the 66v is close enough (?)...

I can fix stuff, but I don't quite know those electrical intricacies yet.

Anyone who KNOWS, I'd love to understand it, and otherwise, ideas welcome.

Thanks in advance everyone!

#6 3 years ago
Quoted from edwood:

So an update, and some help would be LOVELY if anyone can understand what's needed next:
Rebuilt the entire DMD section again... New diodes, and zeners, resistors (ceramics still measured good), all transistors...
Now the voltages are:
66v (instead of 68v)
-110v
-88v (!!?!)
These are voltages AT the pins, DMD unplugged. 12V and 5V still reading good.
So how do I get those extra 10 volts?? Like I wouldn't know exactly which component would be the "likely culprit"...
I would THINK the 66v is close enough (?)...
I can fix stuff, but I don't quite know those electrical intricacies yet.
Anyone who KNOWS, I'd love to understand it, and otherwise, ideas welcome.
Thanks in advance everyone!

Just throw a new board or send it to someone who does repairs...Your time and money You've probably spent double (especially if the boards caught on fire!!) it's not worth the effort.

#7 3 years ago

The DMD is unplugged, right? It's normal for the voltage to be about 20v lower than the anode voltage with no load on the system. The difference is 12v when under load. The 66v should be fine too. It seems to me that everything is good to go.

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