Re: EASY solution for sudden RESET problem on WPC games


"news" <leon.b1@xxxxxxxxxx> wrote in message news:47b08652$0$834$5f6aeac3@xxxxxxxxxxxxxxxxxx
hello again,
i think all points are made in this threat.
Only a few like the solution, most of you guy's will go for the "normal"
repair being perhaps changing connectors and changing BR2 and C5. Nobody
chooses the perfect solution wich cures the real default the low input
tension , that is replacing the 5 volt input transformator with an extra
tranformator that delivers 12 volt AC...
I stick with my solution as i see no damaging something extra with the
additional capacitor, and it's easy to do this mod.
I helps curing a supply fault build in the machines.. Fault wich trigger a
reset when some aging appears on the BR2 bridge or the C5 capacitor. Wich
components are still good but with some aging !( like me LOL!!!)

What i can is honesty report when a machine with the mod will fail again in
that cirquitry for the first time, will it be within moths, a year ,5 years
, 10 years ....
I'll let you know .

I put the info on the end of the page as an extra reference, starting from
today !!

I rest my case
leon


From ST website regarding the linear regulator series:
If large capacitors are used, a high current diode from input to output (1N4001 or similar) should be introduced to protect the device from momentary input short circuit.
From National Semiconductor website:
For output capacitance in excess of 100uF, a high current diode from input to output (1N4004, etc) will protect the regulator from momentary input shorts.

And this:
SHORTING THE REGULATOR INPUT
When using large capacitors at the output of these regulators, a protection diode connected input to output (Figure 1) may be required if the input is shorted to ground. Without the protection diode, an input short will cause the input to rapidly approach ground potential, while the output remains near the initial VOUT because of the stored charge in the large output capacitor. The capacitor will then discharge through a large internal input to output diode and parasitic transistors. If the energy released by the capacitor is large enough, this diode, low current metal and the regulator will be destroyed. The fast diode in Figure 1 will shunt most of the capacitors discharge current around the regulator. Generally no protection diode is required for values of output capacitance ? 10 ?F.

Leon, you have lots of great suggestions and modifications -- and we all appreciate it. Heck, it was you that gave me the idea for the Gottlieb test fixture. But, this is one modification that I don't agree with.

The real fix to this is to use a better voltage regulator....and better alternatives are coming.

-- Ed



"martin" <martin.reynolds@xxxxxxxxx> schreef in bericht
news:aeac3be3-e781-46cc-bbe3-3a98c1285cd2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Feb 10, 10:29 pm, "GPE" <GPE_NoS...@xxxxxxx> wrote:
"news" <leon...@xxxxxxxxxx> wrote in message

news:47aff407$0$835$5f6aeac3@xxxxxxxxxxxxxxxxxx

> Again, the real problem is the low voltage at the input of the LM323
this
> is
> fact that only could be changed by replacing the transformator, i do > not
> think anybody will do that aldo that would be the ultimate GOOD fix ...

> There is no reason the bridge will fail in the long run , neighter the
> LM323
> ( with this fix) .

> Really i don't see the problem

Incredibly HUGE current spikes resulting from doubled capacitance loading
on
the bridge rectifier -- 120 times per second.



> An aswer to Eric, whenever the bridge fails all what happens is that > the
> CPU
> won't start up anymore because of lack of +5.. like in case there was > no
> mod...

> When you install the diode that was suggested in the first answers if
that
> one fails ( shorts) you have about +10 volts on the 5 volt IC's THAT
would
> be a disaster ....

The likelyhood of a failure of reverse biased 1N4000 series diode with
zero
load would be infinitesimally smaller than the likelyhood of the LM323K
shorting and causing the same problem.
You would have about the same odds of this diode failing that you would if
a
transformer shorted out and the bridge rectifier shorted out and the
LM323K
shorted out and forcing the mains voltage onto your CPU board.

I don't see more capacitance on either input or output side being the
cure-all fix for this problem. The only way to fix this is with a better
regulator than the antique LM323.

-- Ed



> In this mod when the new capacitor fails probably the LM323 will die or
> fuse
> will go thats all.No dammage at any baord will occur. When Lm323 fails
or
> C5
> becomes REALLY bad , this will blow a fuse ( C5 shorted) or the input
> voltage will be that low ( C5 no longer good but no short, or LM323
dead)
> that the security ic U10 will do his reset work as usual...

When the LM323 fails -- it has good odds that it CAN short when it fails.





> Guy's thanks for all the answers , i it is very good to remind me at
> possible failiers on the design but up to now there are none... but I'm
> still listening

> Friendly greetings to you all
> Leon
> "Eric Schmitt" <erics.pinb...@xxxxxxxxx> schreef in bericht
>news:83cbd4ba-2756-411d-bd8a-95bf810a15c9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

>> > I found a simple solution to this problem, no need to change the
> rectifier
>> > or the capacitor C5 , no need to take out the power driver board and
> undo
>> > all connectors!
>> > Find the new article on my site under link button 6
>> > Http://www.flipper-pinball-fan.be
>> > leon

>> Yikes! I'd hate to see what happens when your +5 takes a dump, I would
>> probably go around and fuse each component if you want to have that in
>> the game.

>> --Eric- Hide quoted text -

- Show quoted text -

1) I'd rather see this than some of the other things that happen to
WPC power-driver boards.
2) Looking again at the LM323 schematic, a dead short on the input
side causes the output capacitance to do a dump backwards through the
output transistor. Doesn't look like a huge deal to me, but I could
see it being a problem in a design that did it a lot (which would not
be much of a design).



.

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