The +6v is not used for the chips. The +6v goes through discrete
transistors to drive lamps.
Randy
----- Original Message -----
From: "Tom Jennings" <tomj_at_wps.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk_at_classiccmp.org>
Sent: Friday, January 07, 2005 1:19 PM
Subject: RE: RTL Logic
> On Fri, 7 Jan 2005, Cini, Richard wrote:
>
>> OK, this might sound like a stupid question, but being somewhat ignorant
>> of
>> RTL logic in comparison to TTL and other designs, what, if anything, can
>> be
>> substituted for RTL logic chips?
>>
>> For example, if I wanted to build one of Don's devices and I wasn't
>> concerned with using "vintage" chips, could I do it "plug-and-play" using
>> current TTL?
>
> It's an interesting idea. There are different types of RTL,
> wanting supply voltages not +5VDC sometimes. TTL may not like
> running at 6V, the magic smoke may leave. I'd use 74HC instead.
> It will live at 6V.
>
> I doubt any of them would have the same pinouts, first off. There
> would be problems mapping functions (flipflops with right in/out
> combinations, etc) but a few hours with a couple of databooks
> would probably work that out.
>
> You'd probably end up with little daughter boards per-chip, not
> much fun to consider, but if you only need one or two it's
> probably fine. It could be as little as pin swaps and a resistor
> or two, or as much as two chips plus glue passives.
>
> None of the RTL chips have much complexity, so that's a plus.
>
> tomj
>
>
>
>>
>> Rich
>>
>> -----Original Message-----
>> From: cctalk-bounces_at_classiccmp.org
>> [mailto:cctalk-bounces_at_classiccmp.org]On Behalf Of Michael Holley
>> Sent: Friday, January 07, 2005 12:08 AM
>> To: cctalk_at_classiccmp.org
>> Subject: RTL Logic
>>
>>
>> I have acquired some Don Lancaster designs that use RTL logic and I am
>> looking for spare parts. The MC789 hex inverter is used in all of them
>> and I
>> have 2 chips. Does anyone have a reasonable source for the MC789, I can
>> get
>> all I want for $20 a chip.
>>
>> I also have 2 MC799 buffers that are use in the Microlab. I have found
>> two
>> each of these (MC725, MC778, MC785, MC792, MC853, MC855) that I will part
>> with.
>>
>> SWTPC Digital Logic Microlab
>> http://www.swtpc.com/mholley/PopularElectronics/Apr1970/PE_Apr1970.htm
>> Early SWTPC keyboard
>> http://www.swtpc.com/mholley/PopularElectronics/Apr1974/PE_Apr1974.htm
>>
>> I think that Don Lancaster's TIC TAC TOE machine from 1971 is a very
>> clever
>> design. It uses 5 ICs and 60 diodes to play the game. I may build one.
>> http://www.swtpc.com/mholley/RadioElectronics/Dec1971/RE_Dec1971.htm
>>
>> Michael Holley
>> www.swtpc.com/mholley
>>
>
>
>
Received on Fri Jan 07 2005 - 13:26:32 GMT