Help me,Stego!!

Stay cool, Filippo, I´m already here!

Welcome to this forum!

The fault may be very simple. First of all, check the cable and the plug on this cable, coming from the reel motors and going to the module behind the tape drive. Usally this module is named "Ablaufsteuerung".
Very often, the plugs break (after more than 25 years!), and then there is no contact to the module pins.
The cable has one plug and goes to both motors and the break magnet.

If the plug is ok, next check the motor. Unplug the cable (!!!) from the module "Ablaufsteuerung", and check the motor by taking a battery (9-Volts or so), if the motor is spinning. For the test, you must pull away the break pads, so that the motor is not blocked.

The fast spin of the wheels is normal, because if no cassette is loaded and the cassette holder is in "Down"-position, both wheels are turning fast, the left one counterclockwise, the right one clockwise.
If a cassette is inserted, the processor gets information from the white pins (cassette identificator) of the playing time of the cassette. Then the tape drive is windes about 1-2 seconds forward and again back for reading the actual position of the tape. After the time is read in, the display shows "C4" (Tape VCC-480 with 2x4 hours) and the actual position, for example 0.00 for the beginning of the tape, 4.01 for the end of the tape.

And, if one motor is not working, the other is winding the tape, because the faulty motor gives no back pull!

If the fault is not in the plug and also not in the motor, then the next check will be at the output transistors on the "Ablaufsteuerung".
There are 2 transistors on a copper heat-sink. Normally, this are BD898 or TIP125 (Darlington-Transistors). They can also be defective.

So long for the moment. Please check this things, and tell us, what you found out.

Best regards,
stego

(Sorry for my english - my german is better ! But in Italian I have no chance for posting!)

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Stego dear, thanks for your reply and welcome.
My English is very bad.I 'm sorry
I did all the tests that you have written to me
1) the cable is ok.I checked with multimeter
2) I tested with 9 V battery by disconnecting the motor reels cables.it's OK
3) I tried the multimeter with transistor: OK!

Must I to replace some of ablaufsteuerung IC? What is wrong?

Thank you and good night!
Philip

Hello Filippo,

sometimes, the reason for the fault is a "dry" electrolyt-capacitor, located near the copper heatsink. It has 10 µF/16 Volt, and is named C1628 and C1633 (one for each motor output stage).
Please check these electrolyt-caps first, or better: replace them with new ones. Be careful of the polarity of the new capacitors!

It is also possible, that the IC 1620 (LM358) is defective.

I have loaded the service manual for the "Ablaufsteuerung" in this thread:
https://forum.electronicwerkstatt.d.....84308

(Please scroll down!).

Best regards,
stego

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