Are there problems with the default threshold setting on the Applied Biosystems 7500 when using QuantiFast Probe PCR Kits?
FAQ ID -1702

No. We recommend using QuantiFast Probe +ROX Vial Kits: the master mix does not contain ROX dye, but the kit is supplied with a separate tube of ROX dye. The kits allow to adjust the ROX concentration in the master mix according to your cycler’s requirements.

Please follow specific recommendations in the QuantiFast Probe PCR Handbook.