(Topic ID: 145987)

LAH - PS missing -98v


By kcZ

4 years ago



Topic Stats

  • 8 posts
  • 3 Pinsiders participating
  • Latest reply 4 years ago by kcZ
  • Topic is favorited by 2 Pinsiders

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#1 4 years ago

I rebuilt the entire HV side of the power supply... Twice (I'm a dumbass). I still don't have 98v... It is reading 5v. All other voltages are good. Any ideas?

#2 4 years ago

Having 5 volts on the 98 volt line is really odd, is that with the power supply output connectors installed or not?

Can you provide some hi-res pictures of the back side of the board?

#3 4 years ago

Measuring at the PS CN5... Without DMD connected
Pin 1: grd
Pin 2: -5.5v
Pin 3: -110
Pin 4: 65.5
Pin 5: 12
Pin 6: 5
Pin 7: key
Pin 8: notta

Connect DMD and measure at DMD
Blk/yel: -111.2
Gry/yel: -5.6
Yel: notta
Blk: notta
Red: 5
Bly: 12
Prp: 66.6IMG_20151206_155807393.jpg
IMG_20151206_160517710.jpg

You can see my dumbass move on the last pic.... 330 ohm is much different than 330k.

CN6 was never connected during this testing as it results in repeated firing of the auto plunger... Not sure if that is related here?

#4 4 years ago

You can either start tracing the -98 volts back through the circuit and see where it is getting lost or check across board and through board continuity on all of the components you replaced in that circuit. Possibly a through-hole got trashed. I would also check the input voltages on CN1.

What was the issue that made you decide to rebuild the high-voltage?

#5 4 years ago

Dead DMD was the issue.

#6 4 years ago
Quoted from kcZ:

330 ohm is much different than 330k.

330 ohm versus 330,000 ohm resistor. That would put (98^2)/330 = 29.1 watts. I'd say with a nearly 30 watt load on the 330 ohm resistor - he gave up the ghost rather quickly and painfully.

#7 4 years ago

I've checked and checked for continuity. Checked again for the record. Nothing sticking out.

Come to think of things... My dumbass move was putting 330 ohm resistors in place of the 330k resistors at R10 & R11. Upon realizing my bonehead mistake, I did not have any 330k resistors so I reused the old ones. They tested fine with a meter but maybe they are flaky when load is applied.

#8 4 years ago
Quoted from G-P-E:

330 ohm versus 330,000 ohm resistor. That would put (98^2)/330 = 29.1 watts. I'd say with a nearly 30 watt load on the 330 ohm resistor - he gave up the ghost rather quickly and painfully.

It was a rather spectacular fail

Good thing I ordered multiple everything!

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