LC 520 with flaky CRT

[charkes]

Hello,

I just got an LC 520 that's been in storage for years. I removed the battery (no signs of any damage) and cleaned the logic board. When I flipped the power switch, I got the CRT "whomp" charge-up. That happens after I've let it sit for a while before flipping the switch. Otherwise I hear the brief mini-whine from the CRT.

For the first few starts, I could hear a crackly faint chime in the speakers and the CRT would come on bright and clear with a few snaps here and there. I grabbed a BlueSCSI and got a disk image ready for it. Now I attempt to boot it and the speakers let out a full-throated chime but the CRT doesn't come on. I've switched the power off and on (getting the mini-whine) but I haven't been able to get the CRT to come back on.

Any suggestions on what to reflow, recap, or check?


Thanks!

 

[Fizzbinn]

Just to double check as folks often don't know this but the LC 520's rear power switch being switched on will not start the Mac, you need to also press the power key on a connected ADB keyboard.

 

[charkes]

Just to double check as folks often don't know this but the LC 520's rear power switch being switched on will not start the Mac, you need to also press the power key on a connected ADB keyboard.

Yes, I've used the keyboard's soft power to start it. (Thank you for checking.) The rear fan spins, the lights come on, the chime sounds clearly (or staticky). The first few times, the CRT comes on with a flashing question mark.

I'm letting it "soak" for a half hour with the power switch on. Then I'll hit soft power and see if that changes anything.

 

[charkes]

Yes, I've used the keyboard's soft power to start it. (Thank you for checking.) The rear fan spins, the lights come on, the chime sounds clearly (or staticky). The first few times, the CRT comes on with a flashing question mark.

I'm letting it "soak" for a half hour with the power switch on. Then I'll hit soft power and see if that changes anything.

Not any change. Pop of the speakers coming on, fan spins, chime *not* happening this time. Hmm.

 

[Fizzbinn]

My next guess would be the logic board needs a recap...

 

[charkes]

My next guess would be the logic board needs a recap...

Yeah, I'm not getting a chime anymore. I've removed the back shell and carefully set it back up. When I hit the soft power there's the little fizzle of the CRT starting but nothing displays.

 

[charkes]

While waiting on my logic board capacitors to arrive, I decided to test some voltages. While booted, the fan connector is outputting 10.4v and the ADB port is outputting 4.49v. I guess I'll need to order some analog board capacitors as well.