Euzebox running at wrong frequency/no video SOLUTION

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anercomp
Posts: 10
Joined: Fri Jan 09, 2015 4:16 pm

Euzebox running at wrong frequency/no video SOLUTION

Post by anercomp » Mon Jan 25, 2016 11:26 pm

Hey guys, i thought i could share one possible solution to the frequency problem. I built the Euzebox some time ago (i think last year Febraury) and had lots of problems with the frequency. I ordered some 28,63636 MHz Crystals and thought this would just work fine, but it turned out this was just not working. The crystal is 3rd overtone so it worked on a different lower harmonic, a high-pass wouldn't help as i tried. So one thing which helped a lot was a 74HC14, a hex inverting Schmitt-trigger. One side of the crystal on the first input, the other side to the first output. The first output is connected to the second input and the second output connects to XTAL1(pin13). IMPORTANT don't try to use the 22pf capacitors, for me it just messed everything up leading to no frequency. This was working kind of 'random' sometimes it would start with a wrong frequency and when touching and playing around with the crystal/ic it would get the right frequency after some time and would work stabil, but this wasn't really a satisfying result.
So yesterday i desoldered the complete oscillator part and tried to solder it in another place where the pcb wasn't this messed up and tried to get it working stabil.
In the end it was the exact same circuit with one tiny difference: i soldered the case of the crystal to ground and now it works perfect every time! I hope i can help someone with this little advice. Schematic will follow:
euzebox_osc.jpg
euzebox_osc.jpg (36.83 KiB) Viewed 1911 times
Remember: NO CAPACITORS, otherwise it won't work for this circuit :idea:

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