Re: Trying to restore modified Major Havoc board

Ok, I finally got back to this. I replaced the LM324N but it wasn't
actually that the chip was bad... it turned out a lead on a resistor
in that circuit was bent on the underside of the board and shorting
with something else. When I straightened it out, the sound started
working.

However there is still something weird... almost all the sounds are
normal, but a few are wrong. It almost seems like a lookup table for
the sound effects is messed up. The fish robots make weird sounds
when you shoot them, and when you are landing your ship on the
platform, there is a repeating white noise sound instead of the normal
beeping sound. Other than that, I haven't noticed anything wrong with
the sounds... but I can't actually land on the platform because I
haven't figured out the spinner problem just yet.

Any thoughts as to what could cause only a few sounds to be wrong?

On Sat, Aug 20, 2011 at 4:22 PM, Jess Askey <jess@askey.org> wrote:
>  I think that the 2 channels of the pokey are mixed down to 2x2 via
> op-amps... look on the last page of the schems..
>
> http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Major_Havoc/Major_Havoc_SP-252_2nd_Printing.pdf
>
> you might be lucky to just have a bad resistor or cap in one of channels or
> a bad OP-Amp in 14R/S which only affects one channel. 14Q seems to span both
> but you might just have a bad individual op-amp in that IC too.
>
>
>
> On 8/19/2011 4:55 PM, Xyla wrote:
>>
>> Hello,
>>
>> I just picked up a Major Havoc board w/ Tempest adaptor.  I installed
>> it into my Tempest cabinet but things are definitely not right.  I
>> used to own a MH Tempest conversion, so I'm quite familiar with how it
>> is supposed to behave.  And yes, before I even connected it, I flipped
>> the smaller connector.
>>
>> Based on the main symptom, which was that all the vectors were drawn
>> short, and the fact that there is a 12.096MHz crystal on the board, I
>> figured out that someone has modified it for use with an Amplifone.
>> It's definitely a conversion board, with the jumpered pins on the
>> small connector and a serial number starting with CK.  In fact both
>> crystals (a 12.096MHz and 10MHz) have been soldered to clipped leads
>> of previous crystals.
>>
>> The next thing that is wrong with it, is that half of the sound is not
>> working.  To be more specific, it sounds like some voices are missing.
>>  Most of the sounds that do play are explosions, and the theme music
>> at the beginning is only the lower "instrument".  Even the explosions
>> don't sound right though, like they are only partially playing.  The
>> board has a real Quad-Pokey, not an eliminator board… I don't know if
>> this was normal for conversion boards, but my old one had the
>> eliminator daughter board.
>>
>> The display has pincushioning going on, even though the adaptor looks
>> fine.    I can't imagine why.  I also found that when I first
>> installed the boards I had to turn up the brightness on the monitor
>> significantly, and if I turn it up too much the retrace dot in the
>> center is red, rather than white.  Not sure if that means anything but
>> I found it odd.
>>
>> My Tempest spinner does absolutely nothing with MH installed, but it
>> works perfectly with Tempest.  The person I bough this from said his
>> Tempest spinner worked, but slowly.  There is no resistor on my board
>> at R186, which supposedly causes a slow spinner… but I'm not going to
>> go adding resistors if having no movement at all is not normal.
>>
>> Other than all that, the board seems to be functioning properly.
>>
>> So I assume the first thing I should do is replace the crystals with
>> the proper values, but in this document:
>> http://www.ionpool.net/arcade/mh/major_havoc_conversion.txt
>> it says "Also the integration capacitors are DIFFERENT depending on
>> the Y1 clock.  If you change Y1 to a higher frequency, You will need
>> to change the integration capacitor to a larger value (???)."  This
>> part is over my head, and it doesn't help that they don't give any
>> values to compare.  I am hoping someone here can tell me what to look
>> for so I can revert this board to the proper components.
>>
>> My biggest concern is the sound, There is no "P" displayed anywhere
>> that I noticed in the test mode screens, but I don't know if an only
>> partially bad Quad-Pokey would show up.  I was wondering if anything
>> else could be affecting the sound chip (like the crystal speeds) or if
>> I need a Quad-Pokey eliminator board instead?
>>
>> I guess I'll worry about the pincushioning and the spinner after I get
>> the clock speed and sound fixed, but if anyone has any thoughts on
>> those things  too, I'd appreciate it.
>>
>> Thank you for any assistance!
>>
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>
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Received on Sat Sep 3 03:44:53 2011