gtilford wrote:Well, I don't know what to think. I installed the new chip. The measurements look the same. I checked the calibration on my scope. Everything looks okay. I tried both channels on the scope, with 2 different probes. Same result. This is what my waveform looks like with DC coupling.
73, Greg, KM5GT
Hi Greg,
I am wondering what you are expecting from the Si570 and your scope and its probes.
If you have a look at the data sheet for the CMOS version of the Si570, you will find a voltage swing of about 2Vpp at a load of 15pF. Your scope image shows a divisor of 1:1 which corresponds with 200MHz probes mostly to an input capacitance thereof of about 45pF, i.e. about a third of the data sheet impedance definition (neglecting the impedance of the ground strap of the probe which in combination with the input capacitance results in the sine wave). In any case and if possible, you should switch the probe (and the scope) to a divisor of 1:10, but even then the results may be questionable.
Therefore, please follow the proposal of Ron to install U14 and measure the output of pins 5 or 8 of U14 at about 14MHz. If you have a signal at pins 5 and 8 of U14, everything is fine.
73, Rainer DJ6OA