Re: Where to start on Missile Command PCB repair

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 00:35:10 2013