Post Go back to editing

150 khz Tape Bias oscillator based on AD537JH

Hello,

I have an old Tascam 85-16b reel to reel tape machine.
I have a problem of low eraseing causing from a misbehavior of the current master oscillator that producing unstable frequency of 150 - 175 khz (instead of stable frequency of 150 khz).
My question is, can I replace the original oscilator with an AD537JH?
As you can see at the attached schematic, I need a stable frequency of 150 khz with output voltage of +15V /-15V
Please advice.

Parents
  • Hi,

       The AD537 is a voltage or current to frequency converter. In order to produce a stable frequency you need to have a stable and consistent current to drive the AD537. The frequency will change whenever there is a change in voltage or frequency. That means for example you wanted to produce a 150khz frequency, using the f=I/10.5C, using a 10nF timing capacitor, you need to drive by 15.75mA current. You need to maintain this current to produce stable 150khz frequency.

        The fastest way would be to replace directly the oscillator with a commercial one which trimmed to specific frequency. Not sure if there are 150khz readily available in the market. Using the AD537 can also be use, you just need to drive a constant current or voltage source to AD537. May I ask what would be your possible voltage/current source?

    Regards,

    Jonathan

Reply
  • Hi,

       The AD537 is a voltage or current to frequency converter. In order to produce a stable frequency you need to have a stable and consistent current to drive the AD537. The frequency will change whenever there is a change in voltage or frequency. That means for example you wanted to produce a 150khz frequency, using the f=I/10.5C, using a 10nF timing capacitor, you need to drive by 15.75mA current. You need to maintain this current to produce stable 150khz frequency.

        The fastest way would be to replace directly the oscillator with a commercial one which trimmed to specific frequency. Not sure if there are 150khz readily available in the market. Using the AD537 can also be use, you just need to drive a constant current or voltage source to AD537. May I ask what would be your possible voltage/current source?

    Regards,

    Jonathan

Children
No Data