Hey guys! Life is crazy right now, reason why I vanished!
I'll be teaching two different classes, starting next weekend and I need to update some of my material.
Check it out: http://www.zbrushwor...acter-Creation#
Also... I'll be a father for the second time!!!!!!!!!!!! 
On top of that, a TON of work at the studio.
Anyway, I got the 80v transformer last Friday and spent the last 3 hours:
- Assembling a little box/enclosure for it
- Adding an inline fuse
- Wiring both 100v and 80v transformers into a single connector
- Wiring the 12v and 5v into a single connector from the PSU
- Plugging the whole thing to the DMD piggy
- Measuring the loads from the DMD piggy J604 (output to the DMD)
The good news is: everything is going through, all the way to the J604!!!
The not so good news: I'm concerned about the loads I'm reading. I know the tolerance is about 10% and all of them are under the tolerance, which is good:
ideal: my multimeter reads: Tolerance:
125v 136.9v 112.5v - 137.5v
113v 105.6v 101.7v - 124.3v
KEY
GND
GND
5v 5.1v 4.5v - 5.5v
12v 11.5v 10.8v - 13.2v
62v 63.1v 55.8v - 68.2v
Although everything seems fine because they are all under the tolerance, I found some info saying that the difference between the 125v and 113v has to be 12v as a rule. For example, if the -125 volts is measured as -118 volts, the other voltage should be -106 volts.
Here's the complete info I found online:
Testing DMD Voltages.
If the fuses are good on the dot matrix controller board (or audio/visual board for WPC-95), you should next check the power at the DMD itself. Voltages used are +62, +12, +5, -113 and -125. Check these voltages at the dot matrix display, or at connector J604 on the controller board. The pin out is:
Pin 1: -125 volts
Pin 2: -113 volts
Pin 3: Key
Pin 4: Ground
Pin 5: Ground
Pin 6: +5 volts
Pin 7: +12 volts
Pin 8: +62 volts
If the -125 volts is missing, -113 volts will be missing too. All voltages should be pretty much right at the above specs, or within 10%. In regards to the -113 and -125 volts, these two voltages need to be 12 volts apart! So if the -125 volts is measured as -118 volts, the other voltage should be -106 volts. If they are not within 12 volts of each other, the dot matrix controller's high voltage section probably needs to be rebuilt.
Remember the voltages created by the DMD controller card are the -125, -113 and +62. The +5 and +12 volts come from the driver board (if those are missing, and the machine is actually booting, suspect a connector problem on the DMD controller or DMD itself).
Both the -125 and the -113 volts are the same voltage.
The dot matrix display will not work if both the -125 volts and -113 volts measure as the same voltage. These two negative high voltages should be 12 volts apart. The difference in voltage occurs because of diode D6 (D3 on WPC-95), a 12 volt 1N4742 diode. The failure of this diode also kills transistor Q7 (known as Q7 in all WPC generations, a MJE15030). The -125 volts and -113 volts must be 12 volts apart, or the dot matrix display will not work!
The +62 volts drops to +12 volts under load.
When this happens, check transistor Q3 (all WPC generations). This transistor has probably shorted. Also check diode D3.
The +62 volts is not +62 volts.
On WPC-S and earlier games, the positive DC voltage trace that comes from a very small bridge rectifier BR1 is physically routed underneath resistor R9 (1.8k 5 watt resistor). Because of the heat generated by this 5 watt resistor, and the current drawn from the bridge rectifier, this circuit board trace can become burnt and break underneath resistor R9. Because the trace physically runs under this resistor, the broken trace can be hard to see. If the +62 volts is not +62 volts, check this trace.
The -125 volts is too High.
Another problem is the -125 volts is too high, reading instead -140 volts. The usual cause of this problem is a broken trace on the circuit board. These traces are fragile, and the high voltage section of the dot matrix controller can get very hot, and burn them. Use your DMM set to continuity and check all traces.
Rebuilding the Dot Matrix High Voltage (HV) Section.
If the fuses are good, and the display itself is good (tested in another game), it is time to rebuild the high voltage section of the Dot matrix controller board. But before doing that, raise the playfield and inspect all the connections from the transformer in the bottom of the cabinet. Though a rare problem, one of the connectors may have come apart or became oxidized.
After all else is checked, the best idea is to just replace everything in the high voltage section (parts also listed at dmdhv.htm). Note all these parts are also available in kit form from Great Plains Electronics for around $6 per kit. This is a *very* economical way to rebuild the dot matrix high voltage section. The parts to replace includes:
Q6 (MJE15031 or NTE55): Controls the -125 volts (and supplies voltage to the -113 volts).
Q7 (MJE15030 or NTE54/BUV27/BUV28): Controls the -113 volts.
Q3 (Q1 on WPC-95, MJE15030 or NTE54/BUV27/BUV28): Part of the +62 volt section.
Q4,Q5 (MPSD52 or 2N5401/NTE288): Part of the -125 volt section.
Q2,Q10 (Q2,Q3 on WPC-95, MPSD02 or 2N5551/NTE194): Part of the +62 volt section.
D4,D5 (D1,D18 on WPC-95, 1N4758 or NTE5090, 56 volts): Part of the -125 volt section.
D6 (D3 on WPC-95, 1N4742 or NTE142, 12 volts): Part of the -113 volt section.
D3 (D2 on WPC-95, 1N4759 or NTE149, 62 volts): Part of the +62 volt section.
Q1 (2N3904, WPC-S and prior only).
R4,R5 (120 ohm 1/2 watt). Usually Ok, but replace if they look burned.
Check/Replace the Resistors too.
Also check the resistor values. Resistors either work or do not work, and are easily tested (unlike the above transistors). All resistors should be within 10% of spec. Replace any resistors that are out of tolerence or that appear burnt. The 5 watt resistors take the most abuse; if these are working yet cracked, replace them! Always mount resistors slightly above the board to allow air flow below them. On all these resistor, replace if they look at all damaged, even if they measure OK.
1.8k ohms, 5 watts: R9 on WPC-S and prior (R44 on WPC-95).
4.7k ohms, 5 watts: R8 on WPC-S and prior (R43 on WPC-95).
120 ohm, 5 watts: R11 on WPC-S and prior (R28 on WPC-95).
120 ohm 1/2 watt resistors at R4, R5 WPC-S and prior (R30, R31 on WPC-95).
47k ohms 1/2 watt at R3, R6, R12, R13 on WPC-S and prior (R25, R26 R27, R29).
An Alternative to Rebuilding the HV Section.
If the inexpensive HV rebuild kit from Ed at www.greatplainselectronics.com is beyond one's technical skills, there is an alternative to rebuilding the high voltage section. That is to purchase a pre-fabricated board which essentially does the same thing. The DMD-HVP (dot matrix display-high voltage power) board is available from www.pinball-parts.com for about $60. This plugs into and overlays the existing DMD controller board, replacing the original high voltage section on the original DMD controller board. Installs in about five minutes with no soldering. If the original high voltage section is blown on the original DMD controller board, it does not matter (as this completely replaces it). A good alternative for those that have more money than time, or limited soldering skills. Only works on pre-WPC95 games though.
I have some minor critisms with the DMD HV board though. For example, they use the smaller WPC-95 style fuses. Now this would be Ok if the board worked on WPC-95 games. But since it does not, it puts a mix of fuse sizes into a WPC game that otherwise don't use this smaller fuse size. This is bad for the end consumer that may have a supply of stock WPC HV fuses, which now won't work in their game! Also, I feel there should be LEDs for each of the high voltages to show at a glace that -125 volts, -113 volts, +62 volts (and perhaps the +12 volts and +5 volts) were working on the board.
DMD Components by Voltage.
Here are the same list of components, organized by voltage. If only a particular voltage is missing from your DMD, only these selective components can be replaced (not recommended):
-125 volts: MJE15031 transistor Q6 (all WPC versions). MPSD52 transistors Q4, Q5 (all WPC versions). 1N4758 diodes D4, D5 (D1 and D18 on WPC-95). All these components supply voltage to the -113 volt section too. Hence, replace the -113 volt components too.
-113 volts: MJE15030 transistor Q7 (all WPC versions). 1N4742 diode D6 (D3 on WPC-95), which drops the -125 volts down to -113 volts.
+62 volts: MJE15030 transistor Q3 (Q1 on WPC-95). MPSD02 transistors Q2, Q10 (Q2, Q3 on WPC-95). 1N4759 diode D3 (D2 on WPC-95).
The BIGGEST Tip when Fixing the High Voltage.
The single biggest tip when fixing the high voltage section on the DMD controller is this: REPLACE EVERYTHING. This is a high voltage section. This means if all parts were replaced except for ONE bad part, this bad part can cause all the others just replaced to immediately fail! It's just not worth the trouble. Rebuild the whole high voltage section, and replace everything. In the long run money and time will be saved.
This made me concerned and I'm now afraid to test the DMD :-/
My question is: knowing everything is under the limits, should I try to fire it up even if the difference between the high voltages is not 12v, but 31.3v(!!!) instead? Am I risking damaging the DMD if I try?
My second concern/question is: will the 80v transformer be able to handle the load, since the specs are : single voltage winding, 80V (40-0-40) at 20mA center tapped?
Thanks!
-Kris
ps.: things look promising. Wish me luck 
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