Moonferret
Experienced Member
Hi Folks!
Been working on this PET on and off for the past few months but I'm a bit stuck and could do with a few pointers. So far, the following work has been done..
Transistor replaced in the CRT
New 2114 VRAM chips
RAM has been tested OK
Capacitor replaced on the 555 reset circuit
CPU / 6522 checked ok
74LS04 replaced near clock crystal
New set of ROMs burnt
Pettester ROM has been used and runs ok
I've gotten to the point when the machine powers up, you briefly see scrambled characters before the screen is cleared but no BASIC signon message or cursor is displayed. It would seem that its starting ok but is getting stuck after it has cleared the screen. Little unsure how to proceed from here. Possibly an issue with the address lines / decoder?
Cheers,
Dave
Been working on this PET on and off for the past few months but I'm a bit stuck and could do with a few pointers. So far, the following work has been done..
Transistor replaced in the CRT
New 2114 VRAM chips
RAM has been tested OK
Capacitor replaced on the 555 reset circuit
CPU / 6522 checked ok
74LS04 replaced near clock crystal
New set of ROMs burnt
Pettester ROM has been used and runs ok
I've gotten to the point when the machine powers up, you briefly see scrambled characters before the screen is cleared but no BASIC signon message or cursor is displayed. It would seem that its starting ok but is getting stuck after it has cleared the screen. Little unsure how to proceed from here. Possibly an issue with the address lines / decoder?
Cheers,
Dave