how can i check my tension springs for toyota model 7700?

my toyota 7700 has just been serviced and since it has been done the machine keeps jamming up. the serviceman told me he replaced 2 tension springs but the machine just keeps jamming. i also had to change all the settings on everything as they had been set to the maximum this causing the machine to make loud grinding noises especially as i changed direction of sewing.i would really like some input on how to sort out these problems and if possible a glance at a repair manual. my machine has been well looked after.it is also my livelyhood and i cant afford to replace it as i spent my spare cash getting it serviced. i would really like to know where i can get access to a service/repair manual.