I have 3 M200s, all V4, with V2 heatblock/nozzles and having a lot of blobs and a bit of stringing only occuring on one printer.
Using the same material on all of them, same firmware, same z-code, same everything. The nozzle is new, I recently replaced heater/thermocouple, but it didn't help. The only thing that is different is that the one M200 with problems is older than the other two by about 2 years. I maintain all the rods by lubricating them regularly, also making sure that the cog pushing filament is clean. What am I missing?
Fans are ok - I replaced the upper fan not that long ago, the bottom one is ok too. Just curious - how can the pcb, the ribbon cable or weakly tensioned belts cause excessive stringing?
I had blobs and stringing on my V1 printer last week. Changed the heater cartridge and thermo sensor. Works great now! Make sure the set screws are tight on those before you decide to replace.
Fans are ok - I replaced the upper fan not that long ago, the bottom one is ok too. Just curious - how can the pcb, the ribbon cable or weakly tensioned belts cause excessive stringing?
I have not had a problem with a PCB but a ribbon cable supplies the voltage and the heat sensor readings so if it is not conducting properly it could cause incorrect temperature, if the belts don't have enough tension when the head changes direction it could deposit too much material before it starts to move. Try increasing the Fan settings and see if helps, the fan may be running too slow.
Fans are ok - I replaced the upper fan not that long ago, the bottom one is ok too. Just curious - how can the pcb, the ribbon cable or weakly tensioned belts cause excessive stringing?
PCB could be responsible for nearly everything whats wrong with your prints, especially heating issues. I doubt that tightening belts could help in that case but it won't harm, definitely.
Try swapping PCB, ribbon, heater&thermocouple, one at the time.
Lastly, if you wont find root cause, swap motherboard.