Re: Where to start on Missile Command PCB repair

Unless specifically told otherwise (should never happen) a 74LS04 is always
better than 7404.

On Thu, Oct 31, 2013 at 11:35 PM, Grant Thienemann <
grant.thienemann@gmail.com> wrote:

> So I can generally replace a 7404 with a 74LS04 without any problems? I
> actually do have an Oscilloscope but I've never used it expect to test
> Vector PCBs, I use it as a cheap vector monitor.
>
>
> On Fri, Nov 1, 2013 at 12:30 AM, Rodger Boots <rlboots2@gmail.com> wrote:
>
>> 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 00:38:25 2013