sirlemonhead
Member
Hi,
I picked up a really cheap Performa 475 on ebay as the board looked OK from what I could see of the screenshots.
I'm an Apple newbie so even though the auction stated chimes of doom, I figured I might be able to get the board working correctly with little effort - not the case unfortunately.
I have no SIMM installed and no PRAM battery, but I have two VRAM sticks installed. The machine turns on and does the initial BONG noise, then the 8 notes - 4 ascending and then 3 descending which is the chimes of doom I believe? I don't get any video output. If I do the flick on/off/on again trick, I still don't get video ram. I have a new PRAM battery on the way.
The machine seems to have been kept in a damp/humid environment as the RF shield in the case was a little bit rusty, and the VRAM and RAM slots had a handful of corroded pins (somewhat greenish corrosion I think?). The included SIMM actually had most of the gold pins erroded on it's edge connector. The pins of the soldered in RAM chips were a small bit corroded and mostly cleaned up OK.
Some traces near the VRAM and Ram underneath look dark in places but I can't be sure if they're gone or not - I can't get any beep from my multimeter in continuity test when I probe either end of a dark trace using it's via holes. Though saying that, I can't get a beep either from doing similar on a perfectly good via.
PSU appears perfect. It's a Dyna Comp and the capacitors look good and each voltage rail is spot on. The capacitors on the board look perfect - the board was dusty and there was no evidence of cap leakage. Pads appear shiny. I haven't recapped yet but have caps on the way.
I found this thread - https://68kmla.org/forums/index.php?/topic/24711-finally-back-with-some-news-475/&tab=comments#comment-260992, and started checking the pins on each of the on-board RAM chips. I can successfully get continuity between pins A0-A09, RAS, CAS, WE back over to the MEMCjr chip. VCC reads 5v on each chip.
What I can't seem to find is where the data input/output pins are supposed to go - Do these also connect to the MEMCjr chip? or to the CPU? If someone could advise on that, I could start trying to find out of those are OK...
Should I wait and recap the board, or should I keep probing?
I picked up a really cheap Performa 475 on ebay as the board looked OK from what I could see of the screenshots.
I'm an Apple newbie so even though the auction stated chimes of doom, I figured I might be able to get the board working correctly with little effort - not the case unfortunately.
I have no SIMM installed and no PRAM battery, but I have two VRAM sticks installed. The machine turns on and does the initial BONG noise, then the 8 notes - 4 ascending and then 3 descending which is the chimes of doom I believe? I don't get any video output. If I do the flick on/off/on again trick, I still don't get video ram. I have a new PRAM battery on the way.
The machine seems to have been kept in a damp/humid environment as the RF shield in the case was a little bit rusty, and the VRAM and RAM slots had a handful of corroded pins (somewhat greenish corrosion I think?). The included SIMM actually had most of the gold pins erroded on it's edge connector. The pins of the soldered in RAM chips were a small bit corroded and mostly cleaned up OK.
Some traces near the VRAM and Ram underneath look dark in places but I can't be sure if they're gone or not - I can't get any beep from my multimeter in continuity test when I probe either end of a dark trace using it's via holes. Though saying that, I can't get a beep either from doing similar on a perfectly good via.
PSU appears perfect. It's a Dyna Comp and the capacitors look good and each voltage rail is spot on. The capacitors on the board look perfect - the board was dusty and there was no evidence of cap leakage. Pads appear shiny. I haven't recapped yet but have caps on the way.
I found this thread - https://68kmla.org/forums/index.php?/topic/24711-finally-back-with-some-news-475/&tab=comments#comment-260992, and started checking the pins on each of the on-board RAM chips. I can successfully get continuity between pins A0-A09, RAS, CAS, WE back over to the MEMCjr chip. VCC reads 5v on each chip.
What I can't seem to find is where the data input/output pins are supposed to go - Do these also connect to the MEMCjr chip? or to the CPU? If someone could advise on that, I could start trying to find out of those are OK...
Should I wait and recap the board, or should I keep probing?