Re: Galaga - problems setting Rank D

From: Rodney Minch <>
Date: Wed Nov 03 2010 - 20:21:17 EDT

Yes. I checked both of the SIP packages for the dip switches and they
measure 4.7K ohms.

I'm thinking it's probably the 151 chip at 4K is bad. I'll pickup some
tomorrow and see if that does the trick.

Question, is it possible to piggyback a TTL chip like the 74LS151 on top of
another one to see if it's bad?


On Wed, Nov 3, 2010 at 1:55 PM, Franklin Bowen <> wrote:

> Did you check the pull-up resistors to that switch? They are probably in a
> SIP package, which are notorious for failing on Galaga boards.
> On 11/3/2010 1:34 PM, Rodney Minch wrote:
>> I've got an original Galaga board that I've set the dip switches to Rank D
>> (Dip Switch 6J, SW2=On, SW3=Off) but the game shows it's set to Rank C. I
>> can only get the game to show Rank A or Rank C. Basically SW2 is always
>> stuck at Off no matter if the dip switch is set to on or off. I've used my
>> DMM to verify SW2 is working properly. I also verified the trace going from
>> SW2 to pin 3 of the 74LS151 at 4K is good per the schematics.
>> All the other dip switches at 6J are working fine along with all the dip
>> switches at 6K. Any ideas what could be going on here? Could the 74LS151 at
>> 4K be bad?
>> The weird thing is another person local to me had a Galaga board that was
>> doing the exact same thing as this one. Not sure if this is a common
>> problem or what.
>> Any help would be appreciated. Thanks.
>> Rodney

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Received on Wed Nov 3 20:21:19 2010

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