SONY TC-K555ESA: Capstan Motor Board Restoration
Sony decks using the TCM-200Dxx mechanical block suffer from a dreadful capacitor leaking syndrome in various degrees on the linear torque direct-drive BSL capstan motor.
The issue doesn't really manifests itself until the leaking is severe and either the circuit tracks are severed or the the capacitors themselves short-circuit -- unlikely though. I have fixed at least three decks with the same problem.
However once the capacitors start leaking -- which they already did -- the electrolyte is attacking the solder compound. Removal of the capacitors will become close to impossible without the right tools. Let me tell you how I do it. I set the soldering station temperature at 290 degrees Celsius and I apply liquid flux on the surface mount terminals. Then I heat them up while applying some eutectic solder. It takes a little then I can easily remove the capacitors. Cleaning the pads however requires usage of more flux and eutectic solder. Then isopropyl alcohol to cleanup any traces of dirt left.
This is a precision job and if you don't have the right tools then disaster is guaranteed. You will most likely end up ripping the SMD parts off the copper traces. And this spells problems. A restoration is possible but the operation is very laborious. So I would avoid this procedure if I were in that situation.
Anyway let's continue.
This is the capstan motor printed circuit board. What I am looking at is the two SMD capacitors next to the supply capstan flywheel thruster shaft. They are rated 10 uF / 16 V.
Here are the old capacitors removed already.
And because technology evolved and we now have cheap MLCC high-capacity ceramic capacitors, I decided to give up on electrolytic capacitors in these positions. So I went with TDK MLCC miniature capacitors rated 10 uF / 16 V with X5R dielectric. So naturally very stable capacitors.
Clipping the leads to the right dimensions reveals that the SMD pads are perfect for soldering these SMT capacitors. Here they are mounted in happily waiting to do their job for decades to come.
But what are these two capacitors doing anyway? Let's examine the electrical schematics.
Both C905 and C911 are providing power supply rail filtering adjacent to the CX-20174 capstan motor control integrated circuit.
That's it for now.