Re: Where to start on Missile Command PCB repair

Hey Rodger,

Thank you for the information. I'm looking at wikipedia now about the 74XX
series chips, which would be the default standard when looking to replace a
7400, or 7404 etc, would that be HTC?

Thanks
Grant

On Fri, Nov 1, 2013 at 9:08 AM, Rodger Boots <rlboots2@gmail.com> wrote:

> Close. HCT is closer. Either should work.
> On Nov 1, 2013 7:52 AM, "Grant Thienemann" <grant.thienemann@gmail.com>
> wrote:
>
>> Ok not to keep getting off topic, but as this is related to the Missile
>> Command repair, I'm going to ask. When I look for 74191 I can't find
>> anything on Digikey, etc, but when I search for 74HC191 it comes up, is
>> that the same thing?
>>
>>
>> On Fri, Nov 1, 2013 at 8:42 AM, <solarfox@triluminary.net> wrote:
>>
>>> On Fri, 1 Nov 2013 00:35:07 -0400, you wrote:
>>>
>>> >So I can generally replace a 7404 with a 74LS04 without any problems?
>>>
>>> *Normally*, yes, but there *are* cases where you can run into problems.
>>> The
>>> switching speed of 74LS-series parts isn't *quite* identical to standard
>>> 7400-series; the propagation delays of a 7404 vs. a 74LS04, for example:
>>>
>>> -------- 7404 -------- ------- 74LS04 -------
>>> tPLH 12ns (typ) 22ns (max) 9ns (typ) 15ns (max)
>>> tPHL 8ns (typ) 15ns (max) 10ns (typ) 15ns (max)
>>>
>>> (Source: a very dog-eared and well-used copy of "The TTL Data Book,
>>> vol.2",
>>> Texas Instruments, 1985)
>>>
>>> The difference is, admittedly, pretty small, but it can add up when
>>> you've
>>> got signals flowing through a bunch of different gates, or when you've
>>> got
>>> a more complex chip (such as the 74191). So, depending on the circuit in
>>> question, there's a small (but non-zero) chance that you *could* end up
>>> with a "race" condition by swapping a 74LS part into a circuit full of
>>> 7400-series chips.
>>>
>>> --------------------------------------------------------------------------
>>> "I thought I told you to look after him!"
>>>
>>> "He'll be all right; he's a Time Lord."
>>>
>>> "That's just what they're _called_; it doesn't mean he actually knows
>>> what
>>> he's _doing!_"
>>>
>>> --------------------------------------------------------------------------
>>> solarfox@triluminary.net (Gary Akins
>>> jr.)
>>>
>>> --------------------------------------------------------------------------
>>>
>>>
>>> ---------------------------------------------------------------------------
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>>>
>>
>>

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Received on Fri Nov 1 09:17:56 2013