Re: 19K6400

On Fri, 23 Jan 1998, Zonn wrote:
> If you want a reliable monitor for running WG compatible games, your best bet
> will be simply to beef up the weak link in the monitor which is the low voltage
> regulator (get a kit from Anders).
>
> If your looking for a Sega X/Y replacement monitor, then you'll have to do the
> works. You'll also need the transformer used in the Sega game system to run the
> thing. (+/- 50v). At this point a voltage regulator will still be needed. It
> might be possible to use the Anders design to regulate the higher voltages,
> since the regulators are floating. If the output of the regulator I.C. were
> ever shorted to ground, bad things would happen.
>
> Anders: Didn't you say that one side of the supply dies faster than the other?
> Shouldn't there be bypass diodes across the regulator to protect against any
> kind of backward current flow? (I believe John R. asked the same question, but
> I never saw an answer)

Yes, I think the positive dies faster (or negative), at any rate one side
does discharge faster.
As far as putting protection diodes, I did put protection on the Vadj pin
since I added the extra 10uF cap for the increased ripple rejection ratio.
I also put an output protection diode for the output capacitor which is
there to insure we dont get any ringing on the output.
I did not put protection diodes across the Vin/Vout ports of the
regulators.
The reason they are not there is that they are not necessary unless your
output capacitance is greater than 25uF. In this case the output
capacitance is much much smaller than that.
However, if my board were to be modified to work with a higher input
voltage (which is doable), then the protection diodes would have to be
added. This is because the output voltage would be much higher (almost 2X)
Another thing that would have to be added is an overvoltage clamp on the
output of the regulator, since if the Vin to Vout voltage is greater than
40V, then the regulator will burn up. This will not be a problem with
installing it into a standard WG6100.
You must understand, when I designed this upgrade kit it was to fix the
problems with the WG6100 monitor. I never intended to also have it work
for the "sega" type of vector monitor.

> Doubling up the output transistors (without all the other changes) would allow
> the monitor to run a bit cooler, but I wonder if it's really overheating that
> kills the monitor. Somebody really should experiment with transient
> suppressors...

I am going to play around with the TVS protection possibility. Between
some of us, we should be able to get some good info.

+------------------------------------------+
| Anders Knudsen
| ASIC Design Engineer
| Adaptec, Inc., Boulder Technology Center
+------------------------------------------+
Received on Thu Jan 22 18:52:54 1998