Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

[lcdcaps1]

Hi
I have a Panasonic SAPM-31 mini hifi and the tape deck motor keeps spinning all the time
If I just connect the ribbon cable to PCB That is connected to the motor, it spins continuously

If I change the input it still spins

I have put it all back together with all the belts in place and still
I can play, forward and rewind but the motor never stops when I press stop

This never used to happen so I am not sure if a transistor has failed or a diode
I will really appreciate the help from this forum
Thanks all

Here is the service manual
https://www.manualslib.com/manual/14...-Sa-Pm31p.html

[R_J]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

I suspect this is normal as the motor operates the mechanism when a button, ie Play is pressed. The motor runs in tape standby and when you hit IE(play) the plunger solenoid activates the mechanism, as there are no mechanical buttons to engage the mechanism.
If you select CD, does the motor tape motor stop?

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

I suspect this is normal as the motor operates the mechanism when a button, ie Play is pressed. If you select CD does the motor tape motor stop?

Hi
No it does not stop when selecting other modes
I have been told it is not normal and this never used to happen to me before

[R_J]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Hi
No it does not stop when selecting other modes
I have been told it is not normal and this never used to happen to me before

Looking at the logic of Q1314 (page 61) the base should change from 1.9v to 0 volts in standby, this will change Q1314 collector from 10.1 to -0.1 volts
But looking at the voltage on Q1316, it's collector only changes from 0.1 to 0, This suggests the motor - is always low (motor ON)

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Looking at the logic of Q1314 (page 61) the base should change from 1.9v to 0 volts in standby, this will change Q1314 collector from 10.1 to -0.1 volts
But looking at the voltage on Q1316, it's collector only changes from 0.1 to 0, This suggests the motor - is always low (motor ON)

The motor did not used to run continuously
Not sure what's happened for it to start doing it now
It doesn't stop when selecting other inputs Ask when stop js pressed it doesn't stop
Something is up and not sure what
I've read it could be a transistor

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

After checking your voltages
Pin 2 on c309 goes from 2v to 9v on startup and then steady 9v
Q310 collector voltages on startup goes from 2v to 9v
Q310 base has no voltage, when running
When I keep my meter red probe on q310 base I get 1v for a blip and goes to mv

[R_J]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Q310 base is controlled by the logic from the microprocessor. 0 volts on Q310 base means that Q310 is not turned on, so the collector will be high. If you want, short pin2 of cn309 to ground and see if the motor turns off.

These type of tape decks need the motor to be running so that when you press a function, the plunger engages the mechanism WHILE the MOTOR is running. If the motor is not running when you press play nothing will happen.

Tape decks that have levers that you push to engage the mechanism keep the motor off until the mechanism is engaged. This is not how this mechanism works.
The tape motor may turn off after 10min of non use. see if you don't play a tape and let it sit, maybe the microprocessor program will turn it off.

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Q310 base is controlled by the logic from the microprocessor. 0 volts on Q310 base means that Q310 is not turned on, so the collector will be high. If you want, short pin2 of cn309 to ground and see if the motor turns off.

These type of tape decks need the motor to be running so that when you press a function, the plunger engages the mechanism WHILE the MOTOR is running. If the motor is not running when you press play nothing will happen.

Tape decks that have levers that you push to engage the mechanism keep the motor off until the mechanism is engaged. This is not how this mechanism works.
The tape motor may turn off after 10min of non use. see if you don't play a tape and let it sit, maybe the microprocessor program will turn it off.

Thanks for the reply
After looking at the schematic. I can see they state q309 as a plunger switch that works fine
Also stated is q310 is a switch for motor
As the motor is continously on I'm thinking q310 has failed..
The microprocessor seems to be working as all the unit is working
Radio.
Cd
And tape
.if I short pin 2 to ground on cn309 and motor turns off does this mean q310 is faulty

[R_J]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Q310 controls the motor circuit on the tape deck, if bypassing Q310 by shorting cn309/pin2 to ground turns off the motor, that means the circuit on the tape deck is working like it should, this does not mean that Q310 is defective.
You can also check the voltage on CN309/pin2 when you place the whole machine in standby, this should also turn off the cassette deck motor by turning on Q310 causing pin2 to go low

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Q310 controls the motor circuit on the tape deck, if bypassing Q310 by shorting cn309/pin2 to ground turns off the motor, that means the circuit on the tape deck is working like it should, this does not mean that Q310 is defective.
You can also check the voltage on CN309/pin2 when you place the whole machine in standby, this should also turn off the cassette deck motor by turning on Q310 causing pin2 to go low

Thanks I'll try this later .
If the motor does not turn off when shorting pin 2 to ground is q310 the culprit

[R_J]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Thanks I'll try this later .
If the motor does not turn off when shorting pin 2 to ground is q310 the culprit

No. then it is likely Q1316 shorted e~c or Q1314 is bad.

I have see other tape decks that use touch controls for there operation, and they keep the motor running, as that is what makes this type of mechanism work.
If the mechanism engaged before the motor started it would not have the power or momentum to engage the mechanism.

If the motor was not running, when you pressed PLAY there would need to be a delay for the motor to start and get up to speed before the plunger activated the mechanism to engage the tape heads/pinch rollers.

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Thanks for the reply
But this was not happening before. So something is very funny
I'd expect the tape motor to stop when selecting another input
It does not make logical sense to always keep it running even when the radio is selected
I've never seen a transistor with this part number
B1GDCFGH0002
Do you know if there is an alternative please .thanks

[lcdcaps1]

Can't find anything B1GDCFGH0002

Hi
I can't find information on B1GDCFGH0002
What would be a suitable replacement please thanks

[Uranium-235]

Re: Can't find anything B1GDCFGH0002

It's a transistor I'm guessing for a panasonic stereo

[lcdcaps1]

Re: Can't find anything B1GDCFGH0002

It's a transistor I'm guessing for a panasonic stereo

Thanks but need a replacement
Do you know what is an alternative please
Thanks

[R_J]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

They are sometimes refered to as digital transistors, they have internal base bias resistors, look at the number on the part itself.
Measure the internal resistors

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

They are sometimes refered to as digital transistors, they have internal base bias resistors, look at the number on the part itself.
Measure the internal resistors

Thanks for the reply
I'll have a look but can't read the writing on the part
How would I know for sure if it is Q1316 or Q1314

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

They are sometimes refered to as digital transistors, they have internal base bias resistors, look at the number on the part itself.
Measure the internal resistors

Ok so after a lot of cleaning, I managed to get the writing on the transistor
for B1GDCFGH0002
The writing on the chip is
33 07

Can anyone tell me which transistor this is and what replacement will be fine
Thanks

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

No. then it is likely Q1316 shorted e~c or Q1314 is bad.

I have see other tape decks that use touch controls for there operation, and they keep the motor running, as that is what makes this type of mechanism work.
If the mechanism engaged before the motor started it would not have the power or momentum to engage the mechanism.

If the motor was not running, when you pressed PLAY there would need to be a delay for the motor to start and get up to speed before the plunger activated the mechanism to engage the tape heads/pinch rollers.

So i measured the emitter and collector on Q1316
i got 0.8 ohms

so how do i know if Q1316 is bad and so is Q1314
i can buy q1316 easily but q1314 is a pain as nothing is coming up

[lcdcaps1]

Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

Q310 base is controlled by the logic from the microprocessor. 0 volts on Q310 base means that Q310 is not turned on, so the collector will be high. If you want, short pin2 of cn309 to ground and see if the motor turns off.

These type of tape decks need the motor to be running so that when you press a function, the plunger engages the mechanism WHILE the MOTOR is running. If the motor is not running when you press play nothing will happen.

Tape decks that have levers that you push to engage the mechanism keep the motor off until the mechanism is engaged. This is not how this mechanism works.
The tape motor may turn off after 10min of non use. see if you don't play a tape and let it sit, maybe the microprocessor program will turn it off.

i shorted pin 2 to ground on cn309
the motor did not turn off