Monday, September 16, 2019

Sound Technology 1500A Tape Recorder Test System Part II

This guy has been interesting. A computer of sorts from 1980. Removed all the boards and started replacing tantalum capacitors one by one. Once the big values were replaced each board came to life and finally the screen came on. The voltages also were correct.  Next step is calibration and try to pass the self test..


  1. Hi Dear Sir! I wish everyone a very happy New Year.
    I'm a 64 year old electronics engineer from Hungary. I have been working with tape recorders for 40 years, restoring and transforming them. A few years ago I bought the first and only studio tape recorder factory in Hungary called the Mechanical Laboratory, in short Mechlabor. Where the STM-610 and STM-700 were manufactured. I was already familiar with the Sound Technology ST-1500A measuring instrument. But unfortunately, either very expensive devices were only on the market or just malfunctioning. Before Christmas, I managed to pin a partially functional piece, with some minor flaws. This mistake was discussed here by the team earlier, years ago. The monitor error ... What I bought it also breaks down the screen image. The circuit is said to work with a smooth composite video signal. That is why I thought a 5 "LCD video monitor should work with that output. But unfortunately today's trial has failed ... So I ask you if anyone has any info that this company" Sound Technology "
    how to access or how to purchase a service manual for this device. Thank you in advance for your help and understanding!

    Your Sincerely Attila Dragon from

  2. By the way! And what to replace the tantalum ?? Another but new tantalum, or electrolyte baking!

    1. The screen may be fine. We removed all the boards and then power on the unit. Then the screen showed some life. We put each board back in its place. When the screen quit working we worked on that board. Then replaced parts till it started working. Then continued like that. I replaced all tantalums with electrolytics on each board. It was slow and tedious work.


Note: Only a member of this blog may post a comment.