The 35-DMA unit, digital micro ammeter, sometimes causes read error and read value becomes 0. That is, the MA register sometimes becomes 0 after executing the L DMA command. The +5V line near the Tr 14 sometimes drops its voltage when the PRINT ADVANCE signal turns into active. Then, the PRINT ADVANCE signal apparently becomes active again when the voltage drop happens.

Two capacitors, connected to the PRINT ADVANCE signal solve this problem.