WPC Transformers

One of the neat things about pinball parts is the standardization. Seems that even the transformers are similar, but of course there are none available at the usual suppliers. For a transformer, close enough is not always good enough.

WPC went through a couple of evolutions. The first thing is that WPC machines needed a new generation of transformer to provide 50V and 100V a.c for the DMD power circuits. Most of the output windings and connectors are the same across the entire range. However, DCS boards require a 12V winding, not the 18V winding from the earlier systems. This winding drives the power amplifier, which is more sophisticated in DCS machines, but also requires a lower operating voltage. 13491 and onwards SHOULD have common voltages. 12835 and 13491 have a common line voltage connector.

First, the part number history.

5610-12835-00   xfmr-wpc 3 115/230v (18VAC sound)  BR, BSD, BoP, CftBL, DW, FH, FT, GI, HD, HS2, Hot_Shots_Basketball, Hurricane, PZ, Slugfest_92, T2, TAF, TAFG, TZ, WH2O
5610-13491-00   xfmr-wpc power      (12VAC sound)  IJ, JD, Pinball_Circus, Popeye, STTNG

5610-13953-00   xfmr-wpc 94   (female line input)  Corvette, DH, DM, FS, RS, Shadow, WCS

5610-14515-00   xfmer-wpc wide mount               AFM, Congo, I500, JB, JM, NF, SC, SS, ToM, TotAN, WD
5610-14515-01   xfmer-wpc wide mount               AFM, CC, CP, CV, Congo, I500, JB, JM, JY, MB, MM, NBA, NF, NGG, SC, SS, ToM, TotAN, WD

5610-15930-00   transformer p2000                  RFM
5610-15930-01   transformer p2000                  SWE1
 

The WPC machines have the transformer mounted towards the center of the machine. 12835 and 13491 have the same connectors, but different voltages for the sound card. 
WPC-94 kept the transformer in the middle, but moved the voltage selection into the universal power module and switched to the female line connector. Older machines use a pigtailed cable for voltage selection..

WPC-95 moved the transformer to a mounting plate on the back of the machine. These transformers are a bit smaller than earlier models, and have mounting brackets that move the mount screws out (hence "wide mount).

Across all the WPC machines, the output voltages and connections are the same, with the exception of the higher audio amplifier supply voltage in the pre-DCS  machines. . I presume that the larger transformers deliver more power. The earlier machines had more stuff to run.

A WPC-95 transformer with label. P/N 14515-01 from a Monster Bash. Note the warning about not picking up by the leads. This is important.	Here's a 12835 in a Twilight Zone, with a 13491 stacked on top of it. These transformers are mechanically, but not quite electrically, interchangeable. The connectors will all work,  but you will overdrive your DCS amplifier circuits with a 12835 and risk damage.

The output connections. these are the same across all machines. The two pin connector with purple wires is the 100V AC DMD supply. The square connector provides 6.3VAC for GI. Note the yellowing, caused by pins becoming dirty and overheating. The largest connector carries all other voltages. Although it has nine pins, the GI connector only has the one voltage: the windings are connected in parallel, and the extra pins and wires help carry the GI currents.

Output Windings 6.8 VAC 100 VAC 80 VAC 51.4 VAC 16 VAC 13.3V AC 9 VAC 9.8 VAC 18+18 VAC CT    - or -  !2+12 VAC CT

Function   GI DMD DMD Flippers      Flashers     12V digital 5VDC          12V Unregulated sound board power amp

Color   yellow/yellow-white Violet  white/white black-yellow white-red blue-white red white-green gray//white/green 18V for pre-DCS machines 12V for DCS machines

Here's the line voltage input connector. The kicker is, on WPC-94 WPC-95 these connectors are reversed to WPC and WPC-DCS. In other words, the two transformers will plug together, but not into each other's machines. Even stranger, the new connector leaves AC line voltages on unshrouded pins, a potential safety hazard (think about measuring input voltages, and having a probe slip). Most designers put output voltages on shrouded socket-type pins. This connector is a Molex MLX 0.264" pitch connector. You won't find it at Radio Shack, but you will find it at Mouser Molex 19-09-1096 and the male version is Molex 19-09-2099.

Tony Dziedzic warned me that a DCS sound board uses different voltages to the WPC sound boards. So I checked it out, and he is absolutely correct. However, the WPC-95 schematics incorrectly show that the DCS board uses an 18V winding. Tony reports that this error is present on every schematic he has seen.

Measured Voltages (unloaded)

* Original windings destroyed, voltages are from substitute.

Here's the main power output connector, from which the above voltages were measured. The pins are numbered looking into the connector, not from the wire side.The pins are on a 0.2 inch pitch.

Transformer Substitutions
The conclusion I am reaching is that all transformers after the first one (i.e. all DCS transformers) are interchangeable, but might need custom mounting brackets and a new primary connector or a connector adapter.

A DCS transformer can safely be used in a a non-DCS game, but at the cost of lower sound amplifier headroom - distortion at higher listening levels. The earlier games may also have power requirements that are a bit greater than that of newer games (larger transformer) so existing power problems could become worse.

A non-DCS transformer can be used in a DCS game, but will overdrive the amplifier supply, delivering approximately 50V to the TDA2030, which is only rated at 36V. This part gets 36V under 120VAC line input, so it is at the edge to start with. The TDA2030A is rated at 44V, and may withstand the abuse a little better. But don't be surprised if you end up rebuilding your sound output circuits if you try to adapt a non-DCS transformer into a DCS game. The 78L05 regulators used on DCS games to power the analog circuitry should be OK. They are rated for 35V operation (they see 25V in this circuit) and the op-amps and analog output that they power are low-power devices.