Sony STR-DE845 volume drive motor inoperable

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Hi AK,

I have been messing around with the above unit for a few days now. When I originally got it, it seemed to have an issue with the Muting board being intermittently operable, turns out the connector had some dry joints on it, so got that fixed up just fine.

What's bothering me though, is the volume drive motor has given out on me, not really sure why. Suspected it was a dry joint or something so I resoldered all relevant connections, then tested each one for continuity and resistance from point-to-point (I don't entirely trust my meter's continuity test).

When I press UP on the remote, i can indeed see the voltage on the VOL UP pin rise to 4.3VDC, and this change is seen at the motor as well. When I press DOWN, I am only getting about 0.3VDC at the pin and on the motor. There is a +5V pin on this header that I simply cannot figure out the power source of, but that reads 0VDC, something seems amiss with Pin 1 (+5V) and Pin 2 (VOL DOWN). Here is some snips of the schematic, I can upload full pages if needed.

Thanks in advance.

Pins 8 and 4 on the IC seem to be where the 4.5V passes through to the motor on vol down.
IC105.PNG

vol board.PNG

vol board 2.PNG
 
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Pin 8 and Pin 5 of the BA6208F are the logic input pins and the chip is essentially a TTL driven H bridge for reversing the motor.

Datasheet attached.

Check you have the 5v rail- if the associated LEDs on the display are working etc.

Refer the truth table in the datasheet and confirm you are getting the appropriate logic levels to the chip. If you have the correct signals and the 5v supply is ok, the finger points at the 6208F.

Have you confirmed the motor is indeed fine by directly feeding it with 4.5v or so in each direction?
 

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Pin 8 and Pin 5 of the BA6208F are the logic input pins and the chip is essentially a TTL driven H bridge for reversing the motor.

Datasheet attached.

Check you have the 5v rail- if the associated LEDs on the display are working etc.

Refer the truth table in the datasheet and confirm you are getting the appropriate logic levels to the chip. If you have the correct signals and the 5v supply is ok, the finger points at the 6208F.

Have you confirmed the motor is indeed fine by directly feeding it with 4.5v or so in each direction?
This is a solid place to start. I appreciate it. I will do some investigating over the next couple of days, will also try feeding the motor voltage. I will try using a few batteries to operate the motor. What i am seeing, at least with volume up, is an acceptable level of voltage getting to the motor but possible an issue with the negative. Thanks.
 
The motor is still fully operational as confirmed with some batteries. Though, to be honest, I can't understand this particular truth table. I don't really work with a lot of stuff that contains ICs, I usually only service full analog units.
 
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