Replaced a fake ic 601 from AliExpress with another from a legit vendor. The power transistor Q601 supplied by the IC is a surface mount and was bad and the motor would not run , I replaced with a new 2sb798 and it ran (at first fast) but after carefully tracing continuity and resoldering a few points, (including a loose red wire to the speed control pot) it now runs slow (about half speed). voltage to q601 base is 5.1v when "off" and 4.9v when "on". the supply voltage to pin 8 on the IC is 5.7v when off and 5.5 when on. I've jumpered the supply with a 6.o volt "lantern" battery with same performance speed and slightly higher voltages at all points described. With the voltages listed to the base I get only 1.6 v from the collector which supplies the motor. This is as I understand about half the voltage needed. The emitter has the same voltage as the Initial pin 8 IC supply, or the same as the battery (rail) supply, or about 0.6 volts higher than the base pin. Is this just a case of a bad transistor or is there something downstream (or upstream) limiting voltage to the motor? Unrelated to this problem I was able to rebuild the DC-DC converter and now I have sound. Son's friend had fried the converter , ic, and transistor likely with a 9 volt power supply. So is it possibly just a bad Q601? I've contacted @Deb64 and she's been helpful, next step is shipping to her possibly after ok from the 20 year old. Thanks.
