kev308

Hi all, when I run my Tiger I get feedback thru the speaker. It's an HL Tiger with the DBU system. When I start it up it sounds fine, but as soon as I start moving it the noise starts. It's a high pitched whinethat all but drowns out the motor noise. Any ideas why? Or better yet what can I do to stop it?
Thanks for your help, Kevin

yellowshaker

My Feedback: (1)

If it has an RX 18 in it, there is the noise. they all do this...not sure why though

Panther G

Yep, not going to stop it. It is a high frequency electrical noise that cannot be eliminated. Just one of the draw backs of hobby electronics.

kev308

Is there anything I can do to fix it? Cause it's really annoying.

yellowshaker

My Feedback: (1)

Kev, there is no fix for that problem. Panther G meant it is the drawback of toy grade electroncis. hobby grade will not casue this noise. Call me if you want and I can help you out with upgrading the tank to a much better setup.

kev308

Thanks Joe, will do
Kevin

YHR

One thing that you might want to do is power the DBC from a different power source. I use the RX18 with the Benedini system, and discovered the newer RX18s are better, and then when I used a separate power supply to power the DBC the noice was reduced as well.

I posted a thread on this awhile ago. I'll try searching for it and post the link for you.

Here it is

[link=http://www.rcuniverse.com/forum/m_11204147/anchors_11204492/mpage_1/key_/anchor/tm.htm#11204492]DBC mods[/link]

Dan

George Jure

Hello

From reading the posts here I noticed that NO one has said that you should try noise filtering capacitors on the motors. Three non polarised capacitors are placed on each motor,Positve to motor case, Negative to motor case, Positive to Negative and Just for extra insurance motor case to battery ground. Brushed motors have contacts, when the motors are working, turning, they arc and produce high frequency which is usually picked up by near by speakers and they can even effect unshielded electronics. This is the Norm in any R.C boat for example.

George

Buckeye36

My Feedback: (3)

The motors have caps, doesn't help with this.

Buckeye36

My Feedback: (3)

While trying out the modelspiegel gearboxes I found even Tamiyas will whine.
I had the speaker unplugged and could here the same noise (at a lower level) when I drove my Tiger.

strmnd54

The twin RX-18 mod. that I'm using to cancel the track recoil is also eliminating that feedback ; since the motors and the speaker are on 2 different boards...

heavyaslead

A tank filter (i.e. capacitor inductor tunned filter) can be used on the speaker terminals to reduce the offending frequency(s).

If the whine is constant, this method should work well, if the whine changes pitch while running then much less effective.

Off-hand I would try a tank filter tunned to about 15kHz as this (to me) sounds very similar to whine from old CRT television X-ray power supplies.

kev308

How would you wire them in?
Thanks, Kevin

heavyaslead

This pic is the basics of a tank circuit. The values of the components L and C will determine the filtered frequency. The wiring is across the speaker terminals (where the V reference is shown).

The impedance of the speaker will also affect the tank circuit as well as the output circuit (i.e. amplifiler circuit), so a bit of experimentation would be needed to accurately tune the tank circuit.