Teardown and repair of 32″ 1440p Freesync monitor

Introduction

Ever since my dad introduced me to electronics with a soldering iron and Forrest M. Mims’ Getting Started in Electronics, I’ve loved building and fixing electronics. I remember the first electronic project I did completely on my own. In the summer of 1990 (when I was 12-years-old) my dad gave me an audio amplifier kit before heading to work. I guess we were supposed to build it together when he got home. But I was so excited, I whipped out the soldering iron and built it all by myself right there on the carpet – including attaching AC/Mains electricity and hooking up my brother’s Aiwa walkman. I was so proud of myself and so was my dad..

I never had much money to spend on parts, so I would salvage from broken electronics. For example, I would grab old VCRs out of the trash and take them home to de-solder the capacitors and transistors. I did get weird stares from people on the subway in Toronto.

30 years later, I still fix stuff – but rather than scouting people’s trash, I turn to craigslist and get broken monitors. Last year I restored a 10-year-old Dell monitor I got for free by simply replacing a $2 capacitor in the power supply – then I donated it to charity. My latest project was a mostly pristine AOC 32″ 1440p monitor that I got for $25 – it just had one little problem…

Diagnostics

The monitor mostly worked but had a scrambled image on the right-hand side. The backlight was obviously good since both sides lit up at the same intensity. So, I suspected a bad timing-controller board (tCON). Replacement boards for many monitors can be ordered via ebay/aliexpress for $35 so I was expecting to have to pay about that much to fix it.

Screen scrambled on right-hand side

Screen closeup

Teardown

Loosen a single Philips screw between the HDMI and DisplayPort receptacles. Then slip a few guitar picks in between the front and rear plastic housings to release the internal clips.

Rear chassis

Once the rear housing is removed, 4 Philips (+) screws hold the main electronics cage in place. Inside should be a power supply, main pcb, and TCON pcb

Disconnect monitor control button cable

Electronics assembly removed. The main pcb was held in place with 4 Philips (+) screws and the PSU was hidden behind a black plastic cover. Since the monitor mostly worked, I didn’t bother investigating the PSU.

Main pcb is probably used for a few different monitor models. Audio ports, VGA, and an amplifier for speakers are missing on this specimen. The heatsink on the main chip was soldered in place so I couldn’t get a look underneath.

The tCON board was hidden under another black plastic cover and screwed directly into the LCD panel metal chassis stiffener. Two shielded ribbon cable inputs (top) and two unshielded ribbon cable outputs (bottom) can be seen. The controller chip is a Novatek NT71265MFG-001.

Nothing looked wrong, so I unplugged all 4 connectors and re-seated them thinking that might be the issue, but the monitor still didn’t work right. Then I noticed something…

The Culprit and the fix

Like my dad always said, “Just look at it!”

Oops. Apparently when you attach the monitor stand with M4 screws, the screws can punch right through the ribbon cables between the tCON and LCD panel column/row drivers.

The metal bracket lines up perfectly with the hole punched through the ribbon-cable. The screw I pulled out was 18mm but is supposed to be no longer than 10mm!

To verify this was the issue, I swapped the ribbon cables left-to-right and the issue switched sides on the screen. I ordered a few 80-pin LVDS cables from Aliexpress at $1 each with $5 shipping and they showed up 15 days later in a tiny yellow padded envelope. eBay had a few available in the USA but were overpriced at $10-$20 each and would still take almost a week to ship.

Old vs new 80-pin LVDS ribbon cables

The cables were shaped a little differently. Apparently, you can order different profiles that lock into different connector styles. I guess I got the wrong one.

I swear I must have plugged that cable in about 50 times to get it to seat just right. It was ~2mm shorter than the original and wouldn’t snap into place cleanly.

I had to re-orient the tCon pcb to sit at an angle to provide some strain-relief for the new cable otherwise it would pull out causing that side of the screen to go dark.

Sticky tape to hold the ribbon cable down – I added a few more layers after this just in case.

Its alive!

Conclusion

Was it worth it? I think so. A 1440p 32″ 75Hz VA panel monitor is nice, but the tech is a little dated and it’s not as bright or color accurate as the IPS screen I have. Maybe I’ll sell it for $100. $25 + ~$10 in parts and an hour fixing it isn’t too bad. That’s $65/hour! Or maybe I’ll use it to build a Sim racing rig – I have three 1440p 32″ screens now and a force-feedback wheel I got for $50 that I re-built for Forza and Asseto…