Re: Missing caps on Gravitar, Black Widow,

Thanks for the great info.

Here's what I found on the Gravitar board.

C28 was the correct value
C34 missing
C27 was 100uf now .001uf
R46 was 22k now 10k

So I assume someone at some point converted it to a Black widow, then
someone tried to convert it back to a Gravitar and didn't finish replacing
all the caps/resistors back to their original values.

So I now have all the values correct, and the volume is a bit lower, but all
sounds are present.

Thanks guys.

Kevin

On Sun, Jan 23, 2011 at 10:36 PM, Doug Jefferys <dougj@vex.net> wrote:

> Kevin Moore <talon.k@gmail.com> writes:
> >
> > So I've been working on some Black Widow boards, and Gravitar boards, and
> > I've noticed that the caps C34,and C28 are missing. Both these caps are
> on
> > the audio amp circuits for the LM324 chips.
>
> Interesting.
>
> As a point of reference, I have a Gravitar board in which both C28 and C34
> (and all discrete components around B5 and D5) are present.
>
> It's labeled A03898-12 (with the part number in solder mask, the "12" in
> ink).
> It currently runs Gravitar and Black Widow via a bank-switching hack. I've
> forgotten whether I first got it as a Gravitar or Black Widow.
>
> > One Gravitar board someone had placed a cap on it, and I was missing half
> > the sounds from that board until I removed the cap. So I'm wondering if
> this
> > was a design flaw and there was a field service document stating to cut
> them
> > off.
>
> The caps appear to be small decoupling-style caps.
>
> According to TM-232 (Gravitar to Black Widow Retrofit):
>
>
> http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Gravitar/Gravitar_Black_Widow_Retrofit_TM-232_1st_Printing.pdf
>
> To convert a Gravitar to Black Widow, C28 and C34 (0.22uf) "are to be
> removed", because "these components are not used in the Black Widow game."
> C27 (0.001uF) is to be replaced with a 100pF capacitor, and R46 (10 kOhm)
> is to be replaced with a 22 kOhm resistor.
>
> At a glance, I think the only differences are going to be in the volumes
> of the various sounds as mixed through the 7 op-amps (3 at D5, 4 at B5)
> in question, but that just might explain why "half" the sounds are missing.
>
> (My memories of Black Widow in the arcade are sufficiently foggy that I
> can't tell if my ROM-swapped board with Gravitar components still intact
> is inaccurate. Or, if the arcade in which I played Black Widow didn't have
> a tech who took the same shortcut :)
>
> Later,
> Doug.
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Received on Mon Jan 24 12:56:39 2011