New brushless servo HSB-9380TG HITEC with POWERBOX Royal SRS

  • Hello,
    For my future project I plan to use new brushless HITEC servos plugged into a POWERBOX Royal SRS. Iread that HITEC strongly recommands to use a Power Absorbing Device in conjunction with these servos when working with voltage regulators. Could you let me know if it's safe to use these servos with my POWERBOX Royal SRS without these PADs?
    Thanks for your answer.


    Jean-Michel.

  • Richard, to answer your question the HSB-9380 is absolutely designed for giant scale airplanes. It is powerful, very linear, has no slack at centre and uses less power than competitors. The biggest problem is you can't get them because Hitec can't keep up with demand. The only thing is due to its design it generates back power which the devices must be able to accept.
    My latest giant scale warbird uses 5 of the 9380s as well as a PowerBox Royal SRS. I certainly don't want to damage the PowerBox so I will use the PAD devices supplied by Hitec.
    Where do I connect them to the PowerBox, I'm assuming to any empty channel. More importantly, is there any special way I have to configure that port to allow it to accept the PAD?
    I have another project waiting in the wings and it also uses a PowerBox, this time the Competition SRS and will again use Hites HSB-9380 servos so getting this right is important to me.
    By the way the door sequencer is working perfectly now, thanks for your help answering my question on that earlier.

  • Hi Richard, are PAD required also in case of small brushless servos like the Futaba BLS173SV (6.2 kg.cm)? I use them for the nose gear doors controlled by PB door sequencer.


    Kind regards,


    Massimo Aita

  • No,
    the pads are a hitec product designed to be used with their HSB9XXX brushless servo's
    The brushless motor generates a bit of return power and many regulated systems do not like this regenerated power.
    So hitec created the PAD.


    Its not a powerbox item.


    all your questions pertaining to PAD's should be directed to hitec, not powerbox.


    so to sum it up, you only need the Hitec PAD's when you use Hitec HSB 9XXX Servo's.
    The Hitec 7954SH servo's are not brushless.


    http://hitecrcd.com/support/service-bulletins
    June 2014: Brushless Servo Service Bulletin
    While compatible with most radio control devices, the regenerative braking feature of the HSB-9XXX series servos may cause a problem if the device cannot accept a backflow of current. The types of devices that cannot accept this backflow are: Voltage Regulators, Power Safe Receivers and certain BEC circuits whether stand alone or integrated within an Electronic Speed Control. Check with the manufacturer or the Hitec website for a list of compatible models. If your device cannot accept a current backflow, then you must install a PAD (Power Absorbing Device - Hitec PN# 55756) as described in this manual. A PAD is included with every Hitec brushless servo.

  • Hello,


    the PADs are not only brushless related. Hitec servos (high torque or speed) in past also needed this device. The PowerBox doesn´t care about feedback current, you cannot damage it with that. Also the PowerBox has something like PAD inside which works for a certain amount of Servos.
    You may have erratic movements on other servos because of voershoot voltage on the servoside if you don´t use the PAD. For example you controll ailerons and the rudder shows small glitches.
    So if you use high power Hitec servos we recommend to connect one or two PADs on any free PowerBox output.