CMM2 G2 V2 design files

Author	Message
Volhout Guru Joined: 05/03/2018 Location: Netherlands Posts: 5512	Posted: 11:33am 24 Jul 2024       Hi Peter, For testing low pF capacitors, build the LC meter. About crystals. Crystals where typically made from crystal, a glass type that contains lead. Since lead has become more and more banned, the applications where lead is tolerated have become less. So in recent time (last 5-10 years) crystal manufacturers have searched for alternate materials, not containing lead. They have found such materials, but these materials are not capable of handling the same amount of enery. Therefore modern crystals have a lower drive strength, and higher ESR that the classical lead based crystals. Some "older" chips do not have the required gear box in the crystal oscillator circuit to change the gain, and drive strength, to meet these requirements. It is possible that (unintended by either you or JLC) modern parts are used. And by lowering from 10p to 6.8p you compensate for the higher losses in the modern crystal. In changing these capacitors, you will off-tune the crystal slightly, but as long as the VGA monitor locks, that should be not an issue. The STM32H7xx series is not that old, it could have register to adapt the oscillator gain and drive strength... Regards, Volhout Edited 2024-07-24 21:34 by Volhout