I have maranta cd63 which I modified 10 years ago with Ray’s version of the PFM flea to power a tent clock. After taking the unit out of storage, I’m getting a strange signal at the output of the clock and suspect this is the cause of the cd mechanism acting weird (speeding up like mad, with or without a cd in it). Where to start debugging?
(Can’t find a scope photo at the moment, imagine a sinusoid with sharp points)
(Can’t find a scope photo at the moment, imagine a sinusoid with sharp points)
What kind of probe did you use? If it's a 1:1 passive probe, is the circuit designed for a large capacitive load?
When you filter a square wave with a first-order RC filter, you get pretty much the waveform you see. The probe and scope capacitance (typically 100 pF with a passive 1:1 probe, 13 pF or so with a 10:1 probe) could be the C and the output resistance of the circuit under test could be the R. I think you would need something like 100 ohm to 200 ohm with 100 pF (very rough estimate).
I get this with a 1:10 probe. It’s still wobbly, meaning the amplitude of the positive fluctuates slightly. Tried blowing but seems temperature unrelated.
Nonetheless, Seeing this waveform makes me doubt whether the problem in my Marantz cd63 is actually caused by lack/flawed clock signal…
What is the frequency? If over 10MHz, the waveform is dubious.
Also, have you checked the cal on the probe?
Also, have you checked the cal on the probe?