Skateball (MPU) resistor TECH

[tomdotcom]

Hey guys I just got my new rectifier board installed on my skateball.
I got the board from pin-logic.

But, I'm still having an issue with my MPU board. R113 resistor on the
MPU is heating up and burning in the middle basically. I did replace
the old one because it was doing the same thing. It's value is 2k 1/4
watt.

I believe it's +43vdc on connector J4 on the MPU.

Any ideas what might be causing this to happen?

The game lights power up and the machine powers up, but the displays
don't come on and that rectifier burns up on start up. Where do I go
from here?

Thanks!

Tom

[tomdotcom]

Little bit of info I've found so far, still not sure where to go with this:

This resistor takes the 43 volt DC coil power to the zero-crossing detector circuitry and
normally runs hot. Hence it may eventually go open, so check it if
only 5 flashes from the LED are seen.

Interesting...R113 and R16 are part of the Zero Crossing Detector
circuit and go across the 43VDC and ground...for them to go up in
smoke you have to somehow put a LOT more voltage across them...like
200VDC or so...

[tomdotcom]

Got some advice where else to look from a friend. R16 resistor on the MPU is burning/sparking as well.

[tomdotcom]

I measured test point 3 on the MPU. The schematic says it's supposed to be 21VDC but my meter came up as 148.

[Strangeways]

That's an odd problem - Voltages that high would suggest the issue is not the MPU.

Test the Power Supply board - from memory - remove J1 and J3 and then test the voltages on the power supply in isolation. You are looking for the +43V test point.

[tomdotcom]

Alright I'll see what I can do. I'm at a bit of a loss here. I obviously have some power problems. I'm not the greatest with a multimeter though :(

I replaced both burnt resistors. r113/r16 that fried. I'm scared to turn it on now. I don't want to ruin something else :(

[tomdotcom]

Okay I've read through the guide a bit more.

I tested all the test points on the rectifier board (with j1 & j3
unplugged)

Here are the results:
test point 1
6.15

2
149

3
11.22

4
6.6

5
44.4

Here is what the specs are from the manual/repair guides:

    *  TP1 (on AS2518-18) = 5.4 volts DC +/- .8 volts (4.6 to 6.2
volts). Fuse F1, bridge BR1. Used to power the "switched
illumination" (feature lamps).
    * TP1 (on AS2518-49 & -54) = 6.5 volts DC (5.8 to 7.2 volts). Fuse
F1, voltage regulator RP1 and RP2. Used to power the "switched
illumination" (feature lamps).
    * TP2 = 230 volts DC, +/- 27 volts (203 to 257 volts). Fuse F2,
diodes CR1 to CR4. Used to power the score displays.
    * TP3 = 12 volts DC (11 to 16 volts). Fuse F3, bridge BR2. Used to
power the regulated +5 volts DC for the game's logic circuits.
    * TP4 = 7.3 volts AC, +/- 1.0 volts (6.3 to 8.3 volts). Fuse F5.
Used to power the general illumination.
    * TP5 = 43 volts DC, +/- 5.4 volts (47.6 to 48.4 volts). Fuse F4,
bridge BR3. Used to power all the coils.

[tomdotcom]

Okay I should now be testing ALL the wires that go into j1 & j3? To
make sure the proper wire is going to the right place?

How do I test the wires coming into j1 & j3? I have a chart that says
all the proper voltages and what not. But I'm not sure where to put my
multimeter exactly to test each wire individually..

Slowly learning guys..I know alot of my questions sound stupid. But I
am trying. I've got this far, no use stopping now :)

[Strangeways]

Questions are not stupid at all  - we all started somewhere !

OK - TP2 is not right.

You will have to recheck your work from the Transformer to the Rectifier board. I'm hoping the new board came with instructions ?

You really cannot progress until the Test Points are within tolerance.

[tomdotcom]

Yes it has really good instructions. Thanks for understanding :) I'll double check my connections. Is there an easy way to test the values of the wires coming into j1 and j3? The original board was hacked so I had to figure out what he did. I might have missed something. I have all the values of the wires in the intructions. So maybe I could test it that way somehow? Or is that not possible?

[Mr Pinbologist]

Questions are not stupid at all  - we all started somewhere !

OK - TP2 is not right.

TP2 WILL measure 230volts if it is connected to the solenoid driver board, The big capacitor in the hi voltage (not sure of the board reference number without a circuit in front of me) section will make the voltage peak at about 230 volts, so this is quite normal

[tomdotcom]

Mine only measures 149. But that's with j1 and j3 unplugged. Is that normal then?

[Strangeways]

Mine only measures 149. But that's with j1 and j3 unplugged. Is that normal then?

Displays not coming on indicates the HV fuse is dead, or the voltage is too low. They need around 175VDC.

But Mitch indicates it could be normal without load - probably right. Been a while since I've done a Bally - How about testing the theory by connecting up J1 and J3, but maintain that the MPU has its connectors disconnected.

Then you can check TP2 for 230VDC on the Rectifier board

You can also check the test points on the Solenoid Driver board - Check Clay's guide for correct voltages.

Question - When the MPU was in circuit - how many times did the LED flash ?

[Mr Pinbologist]

Mine only measures 149. But that's with j1 and j3 unplugged. Is that normal then?

Yepp thats about right without J1 and J3 plugged in. And roughly 230 volts with J1 and J3 in and no load on the regulator.

[tomdotcom]

The MPU does not flash whatsoever. Zero flashes :/