10x Prescaler for a Frequency Counter

My BK Precision multimeter has a built-in frequency counter feature, but it is only good up to about fifteen megahertz. I put together a 10x prescaler, which (ideally) would enable the multimeter to measure frequencies up to 150 MHz. Two CD7ACT109 Dual J-K flip flops were wired as a divide-by-five counter followed by a divide by two counter. A transistor-based preamp was included to try to improve the signal gain. A switch provides a "pass-though" mode, where the frequency is not divided, as well as the 10x prescaler output. Construction was done in the point-to-point wiring method on portion of a prototyping board. The board in mounted into an Altoids tin using double-sided foam tape, as shown in the first picture. I'm not sure why, but the highest frequency I could measure using the prescaler was about 40 MHz.

This photo shows the prescaler witht he input and output cables attached.