Motor Power Issue

Tascam Porta One Ministudio Tape Deck Motor System

PROBLEM: After years of non-use we decided that we wanted to be able to use the 4-track cassette unit for some music recording. Interestingly the deck mechanism was in the PLAY position even though there was no cassette.

   After inserting a new cassette tape and connecting power it the control buttons (FFW,REW,STOP,etc) did not result in an action of the deck mechanism.

   I noticed that when a button was pressed that the volume gauge lights dimmed and the main Power light blinked.

REACTION: I knew that the problem was power related because of how the Power light blinked. It is designed to blink when the power supply (batteries) runs low voltage. I knew that I needed to investigate inside the unit and so began disassembling.

    When the unit was open I reapplied power and seeked to find any issues. At first I smelled a very faint hot plastic smell, but didn’t know where it was coming from. I then kept the power and play button pressed and then I saw some smoke and was able to find the component that was in trouble.  

  Upon searching the web I did find one forum of helpful folks that did also have a very similar problem.

https://music-electronics-forum.com/showthread.php?t=26474

  After replacing the components the tape deck now operates as it should. I should add that lubrication is important to any mechanical setup like this and so there were a few places I thought it would be good to clean and lubricate (white lithium grease).

  Upon some post-surgery investigation, it looked like the Q1 was behaving as it should. It was the C1 capacitor that seems to be the naughty part to fail the system.

  So nice to have this unit back and functioning.

SOLUTION: The component that was smoking in my unit was the Q1 transistor and it supplies power to the deck motor.

  The person on the forum listed five other components that work with the Q1 transistor. It is decent practice to try and replace all these components as they do work together. The Q1 transistor is obsolete so a suitable equivalent is needed.

Here is a list of the components that can be bought off of Mouser.com   

Q1: 863-2SD1207S-AE                                                                                                                 $0.72
R3: 588-OD152JE 1/4watt 1.5K 5% Carbon Comp                                                                           $0.42
R4: 588-OD333JE 1/4watt 33K 5% Carbon Comp                                                                            $0.42
C1: 647-UVZ1C101MDD (Nichicon) Aluminum Electrolytic Capacitors 16V,100uF                                $0.18
C2,C3: 647-UHM1C471MPD (Nichicon) Aluminum Electrolytic Capacitors 16V,470uF 20% $0.44    (x2= $0.88)