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Old 25th Oct 2018, 2:24 pm   #21
Trigon.'s Avatar
Join Date: Jun 2018
Location: Buckinghamshire, UK.
Posts: 100
Default Re: Retired Texas TI99/4A engineer needs help please.

Originally Posted by Boater Sam View Post
I know nothing of the UA723C or the TL331 chips other than they are hard to source in dil package and that they seem so expensive that I may well be wasting my time trying to go any further with the repair,
The 723 is available from Farnell for less than a pound! - UA723C

As for the TL331C, it does seem surprisingly difficult to find (one on eBay for 5) , but is it actually deceased ? Have you checked to see if the output sawtooth is present ?

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