Monitor Loses Signal During Gameplay – Need Solutions!

Hey everyone! I'm having an issue with my gaming PC that I bought fully assembled. After it arrived, I made a couple of updates: I swapped out the stock cooler for a Rise Mode water cooler and replaced the original 400W power supply with a Corsair 750W, thinking it might help with stability.

However, I'm still facing the same problem. When I launch any game, like CS or GTA RP, my monitor loses signal and goes black, displaying 'no signal.' Meanwhile, the PC remains powered on—fans are spinning, and the keyboard and mouse lights are on. It's strange because my GPU temperature never surpasses 60°C.

Here's my complete setup for reference:
- **Processor:** Intel Core i7-3770 (4C/8T, 3.4-3.9 GHz)
- **Motherboard:** TGT H61-T (DDR3, H61 chipset)
- **Memory:** 16 GB DDR3 (2x8 GB, 1600 MHz)
- **Storage:** Mancer Reaper 480 GB SATA SSD
- **Video Card:** Mancer Radeon RX 580 Streaky 8 GB
- **Original Power Supply:** Mancer Thunder 400W 80 Plus Bronze
- **Current Power Supply:** Corsair 750W
- **Cooling:** Rise Mode water cooler
- **Case:** Pichau Magpie 4B with two fans
- **Monitor:** Mancer Horizon Z3B, 21.5", 100 Hz
- **HDMI Cable:** Pix 2.0 (2 m)

The issues are as follows:
- Signal loss occurs only during gameplay.
- The PC stays on without restarting.
- Peripherals continue functioning.
- GPU temperature is fine.
- I've updated all drivers and switched power supplies.
- Tried different power sockets and cables, but the issue persists.

I'm wondering if anyone else has encountered a signal loss with the RX 580, especially the Mancer versions. Could this be due to electrical instability, a weak VRM, or issues with the H61 motherboard? Any suggestions or tests I should perform? I'd truly appreciate your help!