Portable Panasonic Record Player
 

This is probably a long shot, but does anyone have a dc motor model MHE-5D? I want to try a new motor. Here is the problem. The motor has almost no torque. So, when playing a record it will slow down even slower than it is running. There is a voltage regulator board under the platter. I had recapped the power supply, amp, and replaced the one cap on the regulator board but still the voltage was to low to the motor. Without the motor connected all the voltages on the regulator board are normal. As soon as the motor is connected all the voltages on the board are lowered. It drags the supply voltage down from 10V down to 4 to 6 volts. Only with the motor connected. I have cleaned and relubricated the changer and that is not the problem. The idler is in good condition. It is not slipping, it just cant supply the right current when I connect that motor. It is running it at 3.64 volts. 3.64 volts is correct, however,The motor is spec at 6 to 9.5 volts. The motor runs, but just barely touching it will make it stop. Any ideas, or anyone with a new motor I could buy?

Thanks

Probably not your problem but. A lot of these little DC motors
have a speed control. They often got bad spots on the pot.
The adjustment is through a small hole on the rear with a rubber
cover. Worth a try, its free.
BTW if the speed is controlled by another board there must be feedback
from the motor assy for it to work. Look at that also.

73 Zeno:smoke:
LFOD !

There is no speed control on this motor. It is controlled by the voltage regulator board. It uses a couple of error amp transistors to control current through a transistor. There is an error adjustment on the board, but it must be all the way at one end to even get close to the right output voltage. I suspect there may be a problem with the error amp transistors, but I can't really rule out the motor itself. The board uses a 10 volt supply and it should supply 3.64 volts to the motor. This all checks out with the motor disconnected. As soon as I connect the motor it drags the supply voltage down to less than 6 volts supply and under 3 volts to the motor. If the motor is not the issue, and it may not be, the regulator should see the error and allow the pass transistor to conduct more to make up for the voltage drop. However with the 10 volt supply pulled down so much I don't think it can supply enough current to keep the output voltage at 3.64 volts.
I did disassemble the motor and I noticed a disc capacitor inside. I wonder if it could be leaking? I may revisit this if I can't find a motor.

How much current is the motor drawing from the supply?

jr

Have not checked yet.

Clean the pot contacts and get the voltage adjusted right, if possible. If that doesn't work, it's likely leaky transistor or transistors or motor. Test those regulator transistors if possible, and make sure they're good.

Went through another project and now back on this. I did find an open 12K resistor on the regulator board which I replaced. I have also installed a new regulator transistor. I have just over 10 volts on the supply, but only 2.5 volts to the motor. With or without the motor connected. Way to low. When I connect the motor the supply drops to about 5 volts, but I still have 2.5 volts on the output. Output should be 3.64 volts. I checked the capacitor in the motor and it is not leaky. I didn't think it would be. I suppose next I will finish checking resistors. The error amp transistors check ok, as does the bias diode. I may replace them anyway.

I'd do what you plan on doing. Sometimes transistors do not function in a circuit but test OK. The Bias diode is definitely replace. Best wishes on getting this classic functioning properly again, they're nice little portables.

Today I finished checking all the resistors. They are all within spec. Sams does show a different value for 2 of the resistors. it shows one as 2200 ohm, but the one from the factory is 220 ohms. The other one it shows as 33 ohm, and the factory one is 12 ohm. I did change the bias diode. The error adjustment will change the output voltage from about 2.5 volts to 4.5 volts. It should be able to regulate at 3.64 volts. I did not have replacements for the error amp transistors. I may be back to the motor. It runs, but when it is connected the supply voltage drops to 5 volts with no load. It can supply 3.6 volts at that, but if any load is added to the motor the supply voltage will drop even lower and along with it the voltage to the motor. I am thinking it just cant regulate the voltage to the motor when it loads the power supply so bad. The power supply caps have been changed and it is healthy until you connect the motor.

I have a Panasonic compact stereo where the phono was never used. It has a DC motor and regulator board. The regulator board has two separate pots marked 33-45 and is separate from the motor.
I'll check and see if the motor is the one you need.

Thanks

I meant to get back to you with the part #'s
Motor # MMN-6P2RE, Reg brd# SUP29470C CMKS-47X
If you think you can use them, fine! :thmbsp:

I think that is for a belt drive. It will not work in mine. Thanks for checking.