The problem in finding repetitions using PCR is as follows: In order to perform PCR you splice the DNA in chunks randomly, the length of the chunks depends on the particular machine but it's of the order of 100-1000 bases. Then you need algorithmically find superpositions to reconstruct the original sequence.
If the repeated sequence is longer than the chunk you have no hope of knowing how many times it repeats, if on the other hand it's much shorter (I think it's 6 bases for telomeres) you can see a good number of repetitions per chunk.
If you want to know something more detailed about sequencing and CNV I can send you a couple of sections from my PhD dissertation.
How?