Marantz CD80 tray motor is running non-stop

[Jeph]

I have a modified Marantz CD80 that I have used for years without any troubles, but now the tray motor refuses to switch of. It is permanently trying to pull the tray in, and there seems to be no problem with the switches.

I thought the source of the problem was a dirty connection, because it went away for a couple of weeks after I had taken the main circuit board out and put it back in. But now the problem has returned.

I would really appreciate your help. Thanks in advance.

[Guido Tent]

Originally posted by Jeph
I have a modified Marantz CD80 that I have used for years without any troubles, but now the tray motor refuses to switch of. It is permanently trying to pull the tray in, and there seems to be no problem with the switches.

I thought the source of the problem was a dirty connection, because it went away for a couple of weeks after I had taken the main circuit board out and put it back in. But now the problem has returned.

I would really appreciate your help. Thanks in advance.

are you sure the end-switch makes contact ?

otherwise I suspect a defect transistor in the bridge driving that motor, any chance to measure the control signal ?

best

[Jeph]

Yes, the switch is ok. I can't seem to find a bridge, but the drive to the motor apparently comes from an operational amplifier called TCA0372(A)? Please let me know what I should be looking for.

All help is greatly appreciated. Thanks.

[Guido Tent]

Originally posted by Jeph
Yes, the switch is ok. I can't seem to find a bridge, but the drive to the motor apparently comes from an operational amplifier called TCA0372(A)? Please let me know what I should be looking for.

All help is greatly appreciated. Thanks.

Hello Jeph,

Good. I asked it expicitely as I have been fooled once by my own observation - switch closed, but no contact.....

We certainly need a circuit diagram. I am at home now, but will look at the lab if I can dig up some. Otherwise Jean-Paul could be contacted.

best

[Jeph]

Hello Guido,

I have a diagram right here, and I will try to send you some photos.

Thanks again.

Jeph

[Jocko Homo]

Look at pin 21 (TP 83).

"In/out tray motor
2.5V rest postition of tray
0V opening of tray
5V closing of tray
pulses just after
switch in (S-in)
has been closed."


BTW.....never seen one break.....unlike the -460, which broke all the time.

Jocko

[Jeph]

Hello Jocko,

Pin 21 measures -0.58V.

Thanks for your help,

Jeph

[Jocko Homo]

Minus .58 V????????? How can that be........only +5 on the micro.......unless............

On the bottom of the PCB, there is a zero ohm jumper.........3318, and it goes to 3319.......2.7K. Try scraping off that smd jumper, and ground the junction point. See what happens. Measure pin 21.

(Pull the connector that feeds the tray motor............)

Jocko

[Jeph]

When R3319 was lifted, pin 21 measured 0V. In a private mail Guido Tent indicated that this means that TCA0372 is faulty.

I will try source a replacement TCA0372 quickly, and let you all know if it works.

Thanks again,

Jeph

[Guido Tent]

Originally posted by Jocko Homo
Minus .58 V????????? How can that be........only +5 on the micro.......unless............

On the bottom of the PCB, there is a zero ohm jumper.........3318, and it goes to 3319.......2.7K. Try scraping off that smd jumper, and ground the junction point. See what happens. Measure pin 21.

(Pull the connector that feeds the tray motor............)

Jocko

Hi Jocko

same thoughts across the world :-) (see post below)

-0.58 is a reverse biased protection diode inside the uC

best