problem with northern blot

[belle]

i'm doing my northern blot rite now..but i couldn't get the result..
my film was clear without any trace of expression..
i had follow the method exactly,from the gel seperating,prob labelling,pre hyb and hyb but still couldn't get any result except for my positive control..
but i have got result for my northern last time with faint expression almost not (hard to see),and i'm confused what is it?is it becoz i only exposed the film for 1 day because after i left another film for 3 days i got nothing.but the signal still strong after i check it..so, i'm trying to find a way to solve and troubleshoot my problems.i hope that somebody would help me here..thanks

[danfive]

Things to consider:
1. RNA prep, especially if fresh, if not fresh changes during RNA storage (freeze?, Rnase inhibitor used?)
2. Are looking for very low amounts of RNA?
3. RNA gel electrophoresis worked in first place right?
4. What is the probe you are using?
5. Positive control doesn't create false positives? Does it give a strong signal?
6. What are you using for detection reaction?