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Old Transistors.

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This subject falls loosely under the heading of wiring, so please forgive me if you are expecting to discuss kA and kW. There again some equipment may still have old transistors in it.


I have become addicted to renovating old radio cassette recorders. It has become an obsession. I saw a model advertised on fleabay that I used to own and had disposed of. I bought it with a view to renovating it and enjoying past listening pleasure with some old comedy and music cassettes.


The Philips cassette recorder is a model N2205 and just pays and records on compact cassettes. It is an early 70s model. The motor speed control will not adjust correctly and the player plays at odd speeds. Also the sound output vaires and I have to bang the machine to achieve full sound output sometimes.


The circuit boards use tin cased/ canned AC127 and AC128 transistors which I believe suffer from internal whisker growth that can cause shorts internally.


Are there any plastic cased transistors that are equivalent these days please?


Z.


Parents
  • 0
    I have glued slices of cycle inner tube to rubber wheels that have worn down a bit in the past - though it sound like you are rather beyond that.


    Coming back to the unir with the poor speed control, looking at the circuit on page 6 shows the speed control transistors TS11 TS10 although the drawing rather obscures the

    regulation method and seems to be incorrect when compared to the layout on page7 and a more sensible circuit is redrawn on page13 'the right way up' so it is clearer that most of the motor current goes via TS11 and the diode and  the  other transistor make the regulator and a simple limiter. However, before damning the transistors, I'd verify the voltages are actually varying and it is not just a feature of varying mechanical load, or a scratchy forward/reverse switch. Actully that reg is so crude, silicon devices would probably work without modification, or perhaps a change of resistor value to pull the reference up a bit.
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  • 0
    I have glued slices of cycle inner tube to rubber wheels that have worn down a bit in the past - though it sound like you are rather beyond that.


    Coming back to the unir with the poor speed control, looking at the circuit on page 6 shows the speed control transistors TS11 TS10 although the drawing rather obscures the

    regulation method and seems to be incorrect when compared to the layout on page7 and a more sensible circuit is redrawn on page13 'the right way up' so it is clearer that most of the motor current goes via TS11 and the diode and  the  other transistor make the regulator and a simple limiter. However, before damning the transistors, I'd verify the voltages are actually varying and it is not just a feature of varying mechanical load, or a scratchy forward/reverse switch. Actully that reg is so crude, silicon devices would probably work without modification, or perhaps a change of resistor value to pull the reference up a bit.
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