Need to Clean Hard Drive on an iMac with a Black Screen

[Waverly79]

I would appreciate help with this from anyone who might be able to offer some new ideas.
I have a 24" iMac that after replacing the hard drive and video card last month, Apple store says is probably needs a logic board bc is has a black screen but sounds like it is booting up fine.
I want to sell the computer to someone with more knowledge than me but I want to wipe the hard drive clean. I can't do it that if I can not see the screen and I am not even sure if it really booting up. I have tried the Target Disk Mode with my new iMac but i am not getting anything. The most I see is the old iMac listed as a removable disc but there is not info about it

Super frustrating...
Please help if you can.

 

[Cory Cooper]

Hello and welcome.

If they replaced the hard drive and video card and the issue persists, then it may be the logic board. However, I have seen this issue before, and the fix was to replace the display cable and/or HD cable. If you are getting a chime but no video, then it definitely could be the logic board.

-Does it chime at startup?
-Do the fans spin up to maximum rpm?
-Did they replace the HD and video card? If so, did it work long enough for you to put data on it?
-By chance, have you tried connecting an external display?

C

 

[Waverly79]

It does chime at start up (one time)
The fans do not appear to be spins up to maximum rpm. You can barely hear that it is on, I usually have to feel it to know it is on - I can't really hear it.
They said they replaced the HD and video cord and it was working great for 2 weeks, then I was working, I turned around to do something and turned back around a sec later it was black.
After several random reboot tries I was able to get it to reboot fully and I could see something 1x. I thought I was good but it only last like 4 minutes.
At the Apple store they did try to connect to an external monitor and he got nothing. (In fact he shook his head and said that was weird).
He thought maybe it could be a back light problem but said we would be able to see something if we put a flashlight up to the monitor and we were not able to.

 

[oldscribe]

Hi Waverly79,

I want to sell the computer to someone with more knowledge than me but I want to wipe the hard drive clean. I can't do it that if I can not see the screen and I am not even sure if it really booting up.

If all you want to do is wipe drive and are not worried about logic board screen etc, then why not just put the old HD into an external caddy connect to new iMac and wipe it.

 

[Kaveman]

external screen?

 

[Waverly79]

Thanks for the help. So I did have to remove the hard drive and clean it externally. Logic board was bad so external screen would not work. Thanks Again.

 

[oldscribe]

Hi,

No problem, had feeling logic board was underlying issue.
Thanks for posting back info.