Posted 17 July 2017 - 08:47 AM
First thing I would check or change with a known good one is the cable between the monitor and desktop.
Second thing I would check or change with a known good one is the monitor.
If no good results come from that than it may be leaky capacitors on the graphics card or on the monitor.
Another possibility is a failing power supply.
Lubuntu 16.04 Xenial Xerus (64 Bit) / Dell-Dimension E521 (06/11/2007) / AMD Athlon 64 X2 4000+ “Brisbane” Processor (2.1 GHz, 1000 MHz FSB, 1M Cache, 65W, rev.G1, Socket AM2) / DDR2 Memory 4.0 GB, 677 FSB / NVIDIA C51 [GeForce 6150 LE] Integrated Graphics Adapter.
Linux Peppermint 8 (32 Bit) Dell Optiplex 360 (11/28/2008) / Intel Core 2 Duo Processor E6300 Conroe (1.86 GHz, 1066 MHz FSB, 2M Cache, LGA 775 Socket) / DDR2 Memory 3.0 GB, 800 MHz FSB / Graphics Card Nvidia GeForce 7300 LE [G72] PCIE.