Re: Where to start on Missile Command PCB repair

The L is for low power (lowers speed, too).
The S is for Shotkey (increases speed and power consumption).
LS will draw lower power than a non-LS without the speed loss---is usually
the best part for the job.

On Thu, Oct 31, 2013 at 11:23 PM, Grant Thienemann <
grant.thienemann@gmail.com> wrote:

> Is there a difference between a 74191 and a 74LS191?
>
> Thanks
> Grant
>
>
> On Fri, Nov 1, 2013 at 12:15 AM, Grant Thienemann <
> grant.thienemann@gmail.com> wrote:
>
>> Ok,
>>
>> On Pin 37 I saw a constant 1.971 volts.
>> On Pin 40 I saw a constant 3.7 volts
>>
>> And I noticed this chip is getting hot to the touch in the pictures
>> below, is the one that is brighter than the others
>>
>> [image: Inline image 1]
>>
>> Which if I'm reading the schematic correctly is a 74191. It was just by
>> chance that I noticed that chip was warm, to the tips of my fingers I
>> didn't notice it but on the back of my hand, I thought it was hot.
>>
>> Thanks
>> Grant
>>
>>
>> Suggestions:
>>
>> Processor is 6502A, NOT 6502. Make sure someone didn't stick the wrong
>> chip in there.
>>
>> You can go low-tech if you want, take your DVM and measure processor pin
>> 37. If the clock is there it should read around 2.5 volts. 0 or 5 means
>> clock is missing.
>>
>> Measure pin 40 (NRESET). If 0 volts you're stuck in reset. If around 5
>> volts either game is running or watchdog isn't working. Should be pulsing
>> between 0 and 5.
>>
>>
>>
>>
>> On Thu, Oct 31, 2013 at 8:57 PM, Grant Thienemann <
>> grant.thienemann@gmail.com> wrote:
>>
>>> Hey Guys,
>>>
>>> So I replaced the 6502 socket and all the EPROM sockets as well, did a
>>> quick check and the crystal is on the board, though I have no idea if its
>>> good or not.
>>>
>>> Anyway went to turn on the game and I don't get a loud hmmm anymore, but
>>> nothing is appearing on screen and the game still appears to be dead.
>>>
>>> I need to either figure out how to use my catbox, find a 6502 pod, OR
>>> find my logic probe . . .
>>>
>>> -Grant
>>>
>>>
>>> On Thu, Oct 31, 2013 at 9:02 PM, Matt J. McCullar <mccullar@flash.net>wrote:
>>>
>>>> **
>>>> Nice work so far, Grant. Here is where you can find images showing how
>>>> to "strap" _Missile Command_ boards for different EPROMs:
>>>>
>>>> http://www.ionpool.net/arcade/atari/MC2708.jpg
>>>> http://www.ionpool.net/arcade/atari/MC2716.jpg
>>>>
>>>> You can modify each one of the 4164 RAM chips to "behave" like a 4116.
>>>>
>>>> How to use a 4164 chip instead the original 4116:
>>>>
>>>> - Bend pin 1 und 8 upwards so they no longer go into the socket's
>>>> connectors.
>>>> - Connect Pin 8 and 9 with one another through a short piece of
>>>> wire.
>>>> - Make sure pin 1 and 8 are not in contact with any other
>>>> components nearby.
>>>> - Insert the chip like this into the socket.
>>>>
>>>> (Some gamers who own Williams games like _Defender_ have zillions of
>>>> these RAMs to modify, and it's a lot easier for them to just modify the
>>>> board rather than all the chips. _Missile Command_ doesn't have very many,
>>>> and that's why I like to just upgrade the chips instead.) You do not have
>>>> to change any jumpers on the _Missile Command_ motherboard for this.
>>>>
>>>> I don't have a _Missile Command_ board within arm's reach right now,
>>>> but the crystal is probably labeled "X1" on the motherboard. It looks like
>>>> a small rectangular silver can. (Unless it's missing!)
>>>>
>>>> Hope this helps!
>>>>
>>>> Matt J. McCullar
>>>>
>>>>
>>>
>>>
>>
>

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Received on Fri Nov 1 00:30:56 2013