rna
Well-known member
- Joined
- Nov 20, 2015
- Messages
- 51
So I have a friends mks-80 on the bench which has an anomaly with its earth scheme.
When I first got the machine open I noticed that someone had put a wire link just pushed into the pin headers attempting to join the earth from the MS1 (power) connector to M0 pin 4 (the ground next to the VCA output).
With this wire connected there was a terrible cracking sound and with the wire removed there is a high pitched whistling sound.
The lower voice board works perfectly so I compared the faulty upper board to the lower one whilst fully disconnected. On the working board all Analog Ground pins are connected together but on the faulty board there is no continuity from M0 pin4 Analog Ground to the other Analog Grounds.
I can not seem to find where these 2 Grounds join.
The schematic just has pin 2 and pin 4 of M0 joined together but the PCB traces do not reflect this.
If anyone has a hires scan of the board layout that would be amazing.
I spent some time mapping out the ground scheme, blue shows paths via power connector MS1, and green is the ground path via M0.
When I first got the machine open I noticed that someone had put a wire link just pushed into the pin headers attempting to join the earth from the MS1 (power) connector to M0 pin 4 (the ground next to the VCA output).
With this wire connected there was a terrible cracking sound and with the wire removed there is a high pitched whistling sound.
The lower voice board works perfectly so I compared the faulty upper board to the lower one whilst fully disconnected. On the working board all Analog Ground pins are connected together but on the faulty board there is no continuity from M0 pin4 Analog Ground to the other Analog Grounds.
I can not seem to find where these 2 Grounds join.
The schematic just has pin 2 and pin 4 of M0 joined together but the PCB traces do not reflect this.
If anyone has a hires scan of the board layout that would be amazing.
I spent some time mapping out the ground scheme, blue shows paths via power connector MS1, and green is the ground path via M0.
