UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

SiriusHardware · 13th Jan 2021, 12:57 pm

Leaving the IC in presents a very low risk, but won't really get you any further. Maybe you're asking why not just desolder pin 7 and see if you get an output from it then? The reason is that, as the short you had between pins 7 and 8 has apparently disappeared there is no reason now for the IC not to be able to generate that 1MHz output - unless that output pin is faulty.

If we conclude that the chip now needs to be replaced to rule it either in or out, then of the two possible methods - remove it in one piece or cut it to pieces and remove the pins individually - cutting it to pieces is the better method given the tools which you have.

16-pin IC sockets you can get from just about anywhere but if you want to go UK / British you could try ESR components in Cullercoats or Cricklewood electronics.

The IC, which appears to be a 74191 and not a later 74LS191 (check that by reading the number off the chip?) will have to be obtained from where ever you can find it available. If you are lucky someone here may have one in their box of bits.

13th Jan 2021, 12:57 pm	#102
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,586	Re: Non-working Commodore PET 3016 Leaving the IC in presents a very low risk, but won't really get you any further. Maybe you're asking why not just desolder pin 7 and see if you get an output from it then? The reason is that, as the short you had between pins 7 and 8 has apparently disappeared there is no reason now for the IC not to be able to generate that 1MHz output - unless that output pin is faulty. If we conclude that the chip now needs to be replaced to rule it either in or out, then of the two possible methods - remove it in one piece or cut it to pieces and remove the pins individually - cutting it to pieces is the better method given the tools which you have. 16-pin IC sockets you can get from just about anywhere but if you want to go UK / British you could try ESR components in Cullercoats or Cricklewood electronics. The IC, which appears to be a 74191 and not a later 74LS191 (check that by reading the number off the chip?) will have to be obtained from where ever you can find it available. If you are lucky someone here may have one in their box of bits.