(Topic ID: 233277)

WCS94 Reboots sometimes with both flippers

By apscarpelli

5 years ago


Topic Heartbeat

Topic Stats

  • 26 posts
  • 11 Pinsiders participating
  • Latest reply 5 years ago by Lermods
  • Topic is favorited by 1 Pinsider

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#19 5 years ago

That is somewhat improved, but still incomplete. It's nice to see the authors finally removed the "resistor hack" that used to be listed as the "last resort" and there is now recognition the regulator does lose ability to deliver rated voltage over time (it's part of the newer content that now mentions the PSU5). But there is still no mention of the overload flaw in the 5 volt WPC power system design. Without fully understanding a problem one is unlikely to solve it.

Quoted from Sonic:

I love the Kahr board...I have one... But it's not a fix.... It's a diagnostic tool (everyone debates this)..... It won't fix what is fixable

Thanks for the "love" - your daughterboard is one of nearly 6000 out there... the oldest ones are 5 years old and still delivering. But the "won't fix what is fixable" statement is incorrect - in fact it does fix what is otherwise not addressed in the reset literature - the flawed, overloaded design of the 5 volt WPC power system - there is simply too much load attached to the minimally capable 5v supply. So far the only consistent way to correct that flaw is to reduce the load on the 5v supply and that's exactly what the Daughterboard does. The best practices of maintaining the individual power supplies (bridges, caps, connectors, etc.) are still 100% relevant because the old components do degrade and fail, but the way to get the most life from those supplies is to achieve a better balance of loads across the available supplies.

Quoted from merccat:

If that is it, the kahr is basically the same concept as the ezsbc with the difference that the ezsbc replaces the faulty regulator with a switching regulator in its place. Note that just like the kahr the ezsbc is driving 5v from the 12v line (because that is what drives the original regualtor).

Wrong - replacing the LM323 with a PSU5 doesn't do that at all. It only replaces one component in an under-designed power supply with a more efficient switching device. That doesn't involve the 12v line in any way - the 12 volt line is not a part of the PDB 5v derivation. On the other hand, installing a WPC Power Fix does move the MPU's 5v load off the PDB 5v supply and instead delivers a separate 5v supply derived from the 12v digital supply (this is NOT the supply used by so many mods people like to install). Changing in derivation of 5v for the MPU reduces the overall loading on the PDB 5v supply - that helps stabilize older supplies and at the same time it removes the under voltage sensor from exposure to inevitable machine-wide variations in supply voltage on the minimally designed PDB 5v supply. Note the 12v digital supply is derived from the 18v supply through a 7812 regulator - the large derivation steps offer a good bit of "headroom" to compensate for fluctuations in voltages instead of relaying them through to the MPUs under voltage sensor.

Quoted from NPO:

I say just fix it right the first time and be done with it.

I say that too. By all means, maintain your power supplies as needed to keep them healthy - that can include replacing the LM323 (by the way, the LM7812 is a prime candidate for replacement as well - note that I talk about it here: http://www.kahr.us/index2.html ). And rebalance the machine's power loads with the WPC Power Fix. If you have any inclination to check the indicators, install the Pro version so you can periodically check the relative health of your power supplies over the long term. If you leave out the rebalancing you aren't addressing the root of the design flaw so you will be back in relatively short order poking through the system looking to recover another couple hundredths of a volt.

-Rob
-visit http://www.kahr.us to get my daughterboard that helps fix WPC pinball resets or my replacement LED boards for model H and model S Skee Ball

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