incomplete layers

[mazzi16]

I have an Aurora I3,modified over the last couple of years.The original Melzi board was ok to start with,but the heat bed part died fairly quickly.So I changed the electronics to Ramps 1.4,stuck on a "wade" type extruder,
a hotends.com J-type hotend,and using Marlin and Sli3r.all was going pretty well,but for family reasons,I haven't done much printing in the last year or so.
This week,I needed a part for my quadcopter,but ran into a problem i have not experienced before.
The first layer is very rough,almost like the nozzle was clogged.I stopped the print,and removed the hotend for a thorough cleaning.
There was no great improvement in the quality,but I let the print finish to see what would happen.Sadly,it was a bit of a mess.
Although the part is recognizable( a motor mount),it,s quite obvious that there is a problem.Close observation told me that each layer was incomplete.
It seems that there were 6 to 8 lines being skipped,in 2 or 3 different places of the layer.1 "skip" only 2 lines or so.
I'm wondering whether this is likely to be a hardware problem,or incomplete slicing,or a separate electronic issue.
The surface is also nowhere near as smooth as previous prints had been.I haven't got the part here at the moment,but I will try to post a pic of it tomorrow.

Here,s a picture ,but it,s not too clear.: