[sdiy] ARP Pro Soloist repair needs SN74148 IC..

[Michael E Caloroso]

The LS series are a direct replacement.  They just consume less power
and are slightly faster.

MC

On 6/2/16, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:
> Looking at page 6 of this:
> http://www.ti.com.cn/cn/lit/ds/symlink/sn74ls147.pdf
> I have my answer..
> The LS family has higher input impedance thus for pullup resistors is
> better here..
>
>
> Le 2016-06-02 09:03, Jean-Pierre Desrochers a écrit :
>> I am refurbishing a vintage 1976 ARP Pro Soloist and
>> everything goes well so far.
>> But when removing all socketed TTL IC's one after each other
>> to 'clean' their pins before putting them back in their sockets
>> I noticed one of them had 3 of its pins rusted down very badly and
>> falling off..
>> So I have to replace it.
>>
>> Looking at the service manual:
>> http://www.synthfool.com/docs/Arp/ARP_Pro_Soloist-Service_Manual.pdf
>> pages 54, 55 It's one of the 2 Priority Encoders 10 to 4 Line SN74148
>> (Z1 & Z2).
>>
>> These chips scan many of the presets rocker switches.
>> My question is can I replace the original SN74148 for 74LS148 ?
>> The former is very old and almost gone (unless bought at eBay).
>> So far I found 5 x 74LS148 at a local electronic parts dealer
>> and I think that they will do but I want to make sure with you guys.
>> In the past I replaced many SN74xxx for 74LSxxx but these
>> were in TTL to TTL connections boards.
>> Here its input impedance issues (switches with pullups) I'm aware of..
>>
>> Thanks.
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>
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> avant, personne n'en veut, après, tout le monde le prend. »
> Félix Leclerc
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