I took my 520 STFM (TOS 1.2) out of the garage today (it hasn't been switched on in close to 10 years) and it appears to work okay but for vertical lines across the screen (see photo below) regardless of whether in Low or Medium resolution. It still seems to play demos and boot to TOS etc. etc. and for a brief time they disappeared but then came back
Anyone seen this before and know a cure?