Hello everyone,
I recently bought an iMac G4 15" 700mhz. The machine was a little dirty and missing all the peripherals but the price was low and the screen mechanism works fine so I took it. When I got home I briefly tested the machine, and it booted and worked just fine. The original HDD sounded like it was on its way out, so I ordered a cheap eBay m2 SSD and an IDE-adapter to it (similar I have previously used on Powerbook G4). Also the original speaker was very buzzy and turned out to have melted into sticky goo, so I also ordered a spare part for that.
Now when I got the spare parts, I took the machine apart and put the new parts in. After reassembly, I powered on the machine and it just gave three beeps (at least the speaker works now!). After quick googling I found out that to be sign of memory issue. So I re-seated both the user-accessible and the motherboard RAM sticks, and the machine gave the normal bong sound. But now came the actual issue: while the machine is giving the normal bong on boot, it's not showing anything on screen. I have carefully reassembled the motherboard connections a couple of times, and reset the PMU using the button on the bottom of the machine. The small white led on the display is light up when the machine is powered, so I suppose it's not a display cable issue.
And now to the interesting part. While inspecting the motherboard for any damage I might have caused during the disassembly process, I noticed some really hacky-looking soldered wires next to the cpu. After some research it seems the resistors in the area control the CPU clock speed and can be used to overclock it. I wonder if at some point of previous life of this machine, someone attempted to overclock it, and wasn't very good with soldering? At least some pads seem to be gone and the quality of work is terrible to be honest. But the so-called repair he made seems to have worked, because I was able to initially boot it just fine. My current theory is that when I re-opened the machine I must have broken a poor solder connection somewhere in this bodge wire. It looks like it could break if you stare it long enough.
Now the question is, how to continue from here? Should I try to guess to which point(s) the hacky wire was soldered to, or maybe remove it all and start from scratch? I'm perfectly fine with stock 700mhz, it's not like I'm going to use this machine for anything other than playing around with old OSes and as a nice decoration
I found the G4 700mhz resistor configuration here: https://www.thundernerd.com/iMacG4Chart.html
Looks like its otherwise stock 700mhz, but the left 3 resistors (R252 - 249 + R267 - 265) of both rows are either missing, lost pads or were connected to this mess of wires. Also note that some of the resistors (3 of them) are soldered and are hanging on the wire itself.
Heres some pictures of the motherboard and the resistors. It was a little difficult to take the close-in pictures as I don't have a macro lens and the area is so small, but the pic taken with my phone shows at least something.
I recently bought an iMac G4 15" 700mhz. The machine was a little dirty and missing all the peripherals but the price was low and the screen mechanism works fine so I took it. When I got home I briefly tested the machine, and it booted and worked just fine. The original HDD sounded like it was on its way out, so I ordered a cheap eBay m2 SSD and an IDE-adapter to it (similar I have previously used on Powerbook G4). Also the original speaker was very buzzy and turned out to have melted into sticky goo, so I also ordered a spare part for that.
Now when I got the spare parts, I took the machine apart and put the new parts in. After reassembly, I powered on the machine and it just gave three beeps (at least the speaker works now!). After quick googling I found out that to be sign of memory issue. So I re-seated both the user-accessible and the motherboard RAM sticks, and the machine gave the normal bong sound. But now came the actual issue: while the machine is giving the normal bong on boot, it's not showing anything on screen. I have carefully reassembled the motherboard connections a couple of times, and reset the PMU using the button on the bottom of the machine. The small white led on the display is light up when the machine is powered, so I suppose it's not a display cable issue.
And now to the interesting part. While inspecting the motherboard for any damage I might have caused during the disassembly process, I noticed some really hacky-looking soldered wires next to the cpu. After some research it seems the resistors in the area control the CPU clock speed and can be used to overclock it. I wonder if at some point of previous life of this machine, someone attempted to overclock it, and wasn't very good with soldering? At least some pads seem to be gone and the quality of work is terrible to be honest. But the so-called repair he made seems to have worked, because I was able to initially boot it just fine. My current theory is that when I re-opened the machine I must have broken a poor solder connection somewhere in this bodge wire. It looks like it could break if you stare it long enough.
Now the question is, how to continue from here? Should I try to guess to which point(s) the hacky wire was soldered to, or maybe remove it all and start from scratch? I'm perfectly fine with stock 700mhz, it's not like I'm going to use this machine for anything other than playing around with old OSes and as a nice decoration
I found the G4 700mhz resistor configuration here: https://www.thundernerd.com/iMacG4Chart.html
Looks like its otherwise stock 700mhz, but the left 3 resistors (R252 - 249 + R267 - 265) of both rows are either missing, lost pads or were connected to this mess of wires. Also note that some of the resistors (3 of them) are soldered and are hanging on the wire itself.
Heres some pictures of the motherboard and the resistors. It was a little difficult to take the close-in pictures as I don't have a macro lens and the area is so small, but the pic taken with my phone shows at least something.
