Quoted from wayout440:
G-P-E In your professional opinion is a new supply, even with this design flaw, still a better option than significant repairs to a 20 or 30 year old supply? Another thing to keep in mind is not all aftermarket supplies are the same, with all the different games and aftermarket companies out there. I've only had a few Xpin and Rottendog supplies and they worked very well.
First of all - age is not a deterrence to functionality for solid state electronics. Sure you may need to recap boards and replace connectors. But overall, they were sound designs for decades. Finding replacement parts for often damaged components, on the other hand, may become an issue for 30 year old boards (and some of the new boards). Some parts are NLA and getting hard to find. Always a work around but it still makes it harder to maintain (e.g. 3081 transistor arrays). A replacement is usually better than a board that needs a significant amount of repairs but there are some boards out there that are better than others.
If you look at any board long enough - you can always spot something and think "I can do better". Does it make the original design or the replacement design worse? Not necessarily, mostly just 'different'.
The original boards were solid designs for 20-30 years. But heat and typical 'pinball machine abuse' of electronics takes a toll. There is at least one board maker out there that does not take the abuse very well. For XPin and Alltek boards - I have never had anybody asking for replacement parts. The other board maker you listed is a far different story.
I have seen a minor problem and two major problems with replacement power supply boards:
The minor issue: low voltage supply not having bulk filtering capacitance in addition to the added regulator's input cap (low-ESR, high ripple current). The regulator's are expecting rectified and filtered DC power at the input of their circuitry. This means bulk capacitance in addition to the regulator's input capacitor. Most designers just like to see a separation of bulk filtering and the input cap. However, depending on what specific caps they use for the regulator's input capacitor, this one is easily overcome. Also, paralleled caps tends to work better than a single cap (lower series resistance and higher ripple current capability) - but this is a typical manufacturer suggestion, not an issue.
Major issue 1: wrong type or undersized catch diode in the low voltage supply. This must be a high speed, high current, low forward drop diode to properly supply current through the output inductor. There are many choices but one maker was using 1N5401s in Gottlieb supplies for awhile - until they started burning up. If you have a Gottlieb supply with burnt catch diode, proper replacement would be an 80SQ045N.
Major issue 2: one piece voltage regulators for the high voltage supply. None of the one piece regulators are designed for a 170-190V supply. Some could barely do +125V and others aren't even rated high enough to do the 60V for Gottlieb supplies. I have sold MANY replacement regulators for one of the two supplies you mentioned - and can no longer get the regulators they used (obsolete).
The designers of the replacement boards see the spec "Vin to Vout maximum voltage" and believe they can stay within that. However if somebody shorts the output - I have seen the one piece regulators literally explode. And then there are the turn-on surges where input voltage is up to full voltage and outputs are not yet pulled up (this was the one that the National Semi FAEs warned us about that kill the regulators over time - sort of a death by a thousand cuts issue). Some fast protection has been added by a couple suppliers - if fast enough, it does protect from blowing the regulator but the power-up surges will eventually kill them. Just depends on how often you power up and down the machines.
The only place I can see the proper use of a one piece HV regulator is a Texas Instruments TL783 in a Gottlieb system 1 or 80. For the other supplies, series pass transistor regulators is the only way to go for these supplies. Bally's HV regulator is a series pass transistor and they almost had it right but they used parts that were very close to the absolute max ratings. A bit of beefing up of transistors (such as TIP50 and BUX85 mentioned above), good heat sinking AND current limiting -- these could have been indestructible.