Re: Where to start on Missile Command PCB repair

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 09:08:45 2013