Spool Tape recorder Akai X IV restoration

[ksinbaraj]

hi
I recently had old vintage Akai spool tape recorder model X IV.
It was completely dead and the amp board was faulty. Now I have resorted to some extent that mechanism is working ok and replaced the amp board.

Now I m facing problem in audio playback. I could not get the audio sound from tape head. When I slide the rec/ play switch in the preamp board the sound comes for 2-4 seconds and goes off.
This is almost 40 years old.
I have given the circuit diagram

Can someone pls help me out
Thanks
Inbaa

 

[reubensm]

I have worked on a couple of Akai decks myself. Here are some of my findings (not related to your deck)

1) the R/P switch, especially if its the sliding variety with or without spring loading, tends to get corroded or dusty, this will need to be dismantled and cleaned thoroughly (and better still, replaced it if circumstances permit)
2) legs of transistors tend to rust, and if they are metal cap transistors, the legs rust well up into the housing of the transistor, these need to be identified and replaced
3) Akai generally used high quality capacitors in their reel decks. However I have noticed that sound appearing for a short while and disappearing, sound playing clearly for a short while and then becoming distorted, etc are all attributed to coupling capacitors. Also check capacitors in feedback stages. Never ignore a cap just because it is not a electrolytic cap, good to check all these

In the old days there used to be a small scale industries establishment in Delhi called Business Promotion Bureau. They used to print amplifier and radio circuit books. One common advert in these books used to be that of a signal injector. If you dont have one you can easily build one if you want to. Using this, you can trace the signal path and identify the faulty stage. If you have faulty coupling capacitors in a circuit, this is the easiest way to find out without having to check all the capacitors. However recapping would be required for the electrolytics.