My recently purchased eBay Mac Plus had exactly the same problem. Turn on the Mac and blank screen until you give it a few gentle taps to get the display working. It would jitter especially when the floppy drive was in operation and a few taps were required to get the screen back. After 10 minutes it would be fine.
When I came across Sirwiggum's success, I thought I should give it a go. I hadn't touched a soldering iron for god knows how long... Most probably 20 years so was quite nervous doing this fix.
I was a bit lazy at first and just heated the old solder on J4... This made the jitteriness on the screen worse! So, I went out to the shops and purchased some new solder and carefully refreshed the J1 and J4 connections. I became confident and with the soldering iron and made the connections neat and clean.
When I switched the Mac on, I was really chuffed to see a perfect display with no jitters - even with the floppy operating. I'm really proud that my Mac Plus is working 100%. Thanks everyone!!!
When I came across Sirwiggum's success, I thought I should give it a go. I hadn't touched a soldering iron for god knows how long... Most probably 20 years so was quite nervous doing this fix.
I was a bit lazy at first and just heated the old solder on J4... This made the jitteriness on the screen worse! So, I went out to the shops and purchased some new solder and carefully refreshed the J1 and J4 connections. I became confident and with the soldering iron and made the connections neat and clean.
When I switched the Mac on, I was really chuffed to see a perfect display with no jitters - even with the floppy operating. I'm really proud that my Mac Plus is working 100%. Thanks everyone!!!