Hey guys I have a Textronix 531A, once I changed the plug-in that was in it, it worked perfectly. I'm working on an FM radio and I'm trying to measure the oscillator frequency which is 90 Mega Cycles. So I'm looking for a plug-in that will allow me to run at that speed. I currently have the type K plugin. Which I think is only good for 15 MHz. I see there's a 1A7 that looks very fast will my scope accept that? Or is there other good choices? I have a Tek 536 also that worked once I changed the plugin. If that is a better choice to use, I'm willing to use that.