11-06-2024, 12:55 PM
(This post was last modified: 11-06-2024, 12:58 PM by ppppenguin.)
I've replaced a dead chip and it's much better now. Working without extender boards is a PITA. i have to solder wires on to each point I want to probe and put the card back in its slot.
I was looking at 70ns pulses once per field which is very difficult on any analogue scope except perhaps the Tek 2467 with its microchannel plate CRT. I don't have one, only a 2465B which could do it, but only in a well darkened room. My Rigol digital scope made it easy.
Much patient probing revealed a dead 7474 (dual D-type flipflop). This is part of an 8 bit counter that takes data from the core memory and passes zero at the right hand edge of the circle. I used a 74LS74 as I didn't have any 7474. Replacing standard TTL with LS is usually OK unless an output is driving a very heavy load.
There's at least one more fault but this is a huge improvement.
I was looking at 70ns pulses once per field which is very difficult on any analogue scope except perhaps the Tek 2467 with its microchannel plate CRT. I don't have one, only a 2465B which could do it, but only in a well darkened room. My Rigol digital scope made it easy.
Much patient probing revealed a dead 7474 (dual D-type flipflop). This is part of an 8 bit counter that takes data from the core memory and passes zero at the right hand edge of the circle. I used a 74LS74 as I didn't have any 7474. Replacing standard TTL with LS is usually OK unless an output is driving a very heavy load.
There's at least one more fault but this is a huge improvement.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
