Quote Originally Posted by skeptic
Head misalignment is probably the number one cause of high end rolloff requiring a technician's assistance. That's a very good place to start. Make sure the heads are clean too. That's an even more common cause of high end rolloff. Even the slightest film of oil from your fingers or oxide buildup can cause a high end rolloff. I use pure alcohol and a cotton tipped swab on mine. That seems to work well. Just keep the alcohol away from the rubber pinch rollers. Demagnetizing the heads also might help.

Thanks for the clarification chance.
Thanks for your answer. I have tried all of above method before I wrote this BBS. So now I am thinking of that the playing EQ in this deck has not been set as the standard one which is type 1 tape, 120US, type 2 75US. And I am now trying to re construct the circuit but with only a little result. I am seeking help from you guys.