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

SiriusHardware · 23rd Feb 2021, 6:04 pm

We know that UD7 should be good and I'm confident that UD6 was too.

If we assume they are, then there are some possibilities -

-Not all data lines of UD6 / UD7 making it back to the CPU due to a bad socket pin or some other lost connection between the two.

-UD6 / UD7 not being selected when they should be due to an address decoding fault or an address line fault on the way to the address decoder

-Missing address line on the way to the PROMs

-UD6 / UD7 both being selected at the same time (clashing) due to similar problems to above.

-Faulty data bus buffers loading the bus just enough to upset it when certain other devices are also connected.

Time to go home. Later this evening we'll have a look at what the chip select lines on those two PROMs are doing, if anything.

23rd Feb 2021, 6:04 pm	#627
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: Non-working Commodore PET 3016 We know that UD7 should be good and I'm confident that UD6 was too. If we assume they are, then there are some possibilities - -Not all data lines of UD6 / UD7 making it back to the CPU due to a bad socket pin or some other lost connection between the two. -UD6 / UD7 not being selected when they should be due to an address decoding fault or an address line fault on the way to the address decoder -Missing address line on the way to the PROMs -UD6 / UD7 both being selected at the same time (clashing) due to similar problems to above. -Faulty data bus buffers loading the bus just enough to upset it when certain other devices are also connected. Time to go home. Later this evening we'll have a look at what the chip select lines on those two PROMs are doing, if anything.