Screen Issue cannot find correct answer

Hi all, from reading a bazillion posts, fixes, possible causes I’m exhausted!

My issue hasn’t been exactly described by anyone so far so I’m HOPEFUL my answer will come here...

BACKGROUND STUFF THAT BOTHERS ME

1. My iMac was recently transported over 600klms & handled by courier/depot/courier although it was pretty well protected.

2. Once it arrived, before I could use it I had to get a tech to get in and get me going after it was sitting unused for 3 years due to locking myself out but having a MacBook Pro on hand I just moved onto that rather than coughing up to get it sorted at that time. Was out of work soon money really. He backed it up & reinstalled OS10.? (El Capitan anyway).

3. My bro forgot to pack the power cord when he shipped it up to me so the tech gave me a generic cord to use. My plugin keyboard cord which was also shipped to me, had a break in at where it joned the keyboard so the guy gave me a wireless Mac keyboard

(he kept my MacBook Pro for parts in exchange as it was wrecked he said. A small bug of some kind had crawled inside it & died, leaking body fluids onto the logic board which was too damaged to fix and expensive to replace he said even IF he could locate one as they no longer make them for that model).

4. Back to my iMac8,1 (April 2008)

After getting it back all worked just fine for about one week.

Suddenly one day the screen did a few little flickers while I was designing a website (online). Oh oh. Worked fine for several more hrs until I turned it off & went to bed.

Next day when I started it up, I got a black screen immediately after the login screen, so I couldn’t see where my cursor was & therefore couldn’t log in.

Changed keyboards (found I had a Logitech one I bought to use with my iPad ages ago).

THAT WORKED. So I figured it was the keyboard!

Next day (after again shutting down overnight) BLACK SCREEN again.

Hunted all over the web and have tried the “normal” resets (VRAM, PRAM, holding down shift key, grrrrrrr every possible key combo offered.

Left it for 4 days this time and had ANOTHER go this morning.

THIS TIME with brand new batteries in the Mac wireless keyboard (the Logitech keyboard only worked ONCE until I shut down overnight. Never since.

It worked! Changing the batteries to brand new suer duper ones worked!

FOR ABOUT 45 SECONDS!

The screen was lit and I was about to start work after logging in when the flickering started. It went BLACK. I was so pxxxxed off I shook the screen a bit in frustration.

THAT MADE IT COME BACK ON! Mmmmm. Not for long though. Shaking it DID work a couple more times (changing the angle of the screen did too once!).

But it’s all over again now. A short lived ray of hope.

Can anyone make anything of my story that would make sense?

I’m on a pension, trying so hard to start an online biz training site to help me financially but without my iMac it’s going to be impossible.

I’m PRAYING it could be that something is just loose!

What would you suggest?

MEANTIME

I have a Samsung smart tv I think I could use as my screen if only until I can afford to get my iMac fixed or buy a new one once my biz gets going.

I could afford the small cost of buying the right cord to adapt it to since my iMac doesn’t have a port for the hdmi cable I understand I would need. So any help on that’s ore would be appreciated too so I get the right part!