Output of tascam 42B down at 7 5 ips

Hello,
Test tape playback on my Tascam 42B is down 6db as compaired to 15 ips which has no drop. Is it a bias Adjustment or malfuction?
Help anyone?

Inside the unit, on the circuit board, there is actually a separate control for playback level, for 7.5 IPS.
AND there is a separate level control for 15 IPS.
To find the controls, you may need to have the service manual.
And yes the 7.5 playback EQ may not be adjusted for the type of tape you are using. Again, on the circuit board.
Whenever we talk about using a test tape, we are also talking about adjusting all the trim controls inside the unit. There's lots and lots of them.