The schematic for the suspected area is here:
Symptom: Most of the time when in play/rec the takeup reel will stop for maybe 1/4 second. it will do this three times and then stop. Sometimes it has no problems. It seems to get more stable the longer it runs. Interestingly, the transport buttons do not function during the failure mode so I have to wait for it to glitch a few times and then stop itself.
I did all the normal stuff like resolder suspect joints, check connections, etc. Didn't find anything. Pulled caps that seemed to be related to the motor controller & checked them. They all tested good.
Checked the Hall sensors & am getting what look like good pulses all the way back to the CPU.
Checked the motor controller (IC0006 on board MIX3/7). When the unit is working normally I measure <1V on pin 6 but when things are going poorly I measure 9V.
Does anyone know if this is a known failure mode of the unit or have any other advice? I'm kind of wondering if either Q014 or the motor controller is bad. The periodic "glitching" of the transport makes me think that it's some kind of capacitative issue but I haven't found it if it is so that makes me lean more toward the motor controller since I suppose that kind of thing could happen inside the chip.
I'm trying not to shotgun parts in so thanks for any advice on this.
dave