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schlae / snark-barker-mca

A Sound Blaster compatible sound card for Micro Channel bus computers
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NE558 Fakes or a bug? #6

Open vossi1 opened 3 years ago

vossi1 commented 3 years ago

Hi, sadly I just got the next batch of non working NE558 :( My desoldered SEC KA558 from an ESS Audio Card works perfectly... Is it possible that the card doesn't like all 558-timers???

I tested the signetics timers on a breadboard with a large cap and resistor to get a calculated 1 second pulse - that works with all timers in the 558 and exactly the same with the old SEC KA558 chip - no difference!

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vossi1 commented 3 years ago

OK, I tested all 558's in my ESS audio drive in an ISA model 30/286 - all are ok! So we have a bug!

Why only the SEC KA558B works and all other original Signetics 558 doesn't work in the Snark Barker MCA? Is there a difference in the design? I tested the SB MCV in my 70/16MHz and in the 95/P90. In both machines only the Samsung 558 works.

I will check the circuit design on my SB 2.0 ISA - and check how they use the 558...