Re: HP 9821 - display and tape transport issues #VintageHPComputers

Dave McGuire

On 2/3/20 4:46 AM, Achim Buerger wrote:
The 'die without notice' applies to all TTL chips made by NI in the
early 1970s. I had to replace dozens of ICs in my various 98xx
calculators and peripherals and in 99% they where made by National
Instruments. If I get a defective 98xx board I first check all NI chips
by means of a logic comparator. NI seemed to have problems with long
term stability of their TTL ICs in the 1970s. The dying already began in
the 1990s and still continues. Some times I thought about exchanging all
NI chips prophylactic, but that would cause a lot of work in my ~20
devices. Moreover, some chips are hard to find these days.
Pretty sure you mean "Texas Instruments", not "National Instruments".


Dave McGuire, AK4HZ
New Kensington, PA

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