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Author Topic: JJC sound unit  (Read 2332 times)

boatmadman

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JJC sound unit
« on: April 04, 2016, 07:05:20 PM »

Having acquired an old jjc sound unit, the v8 one, I am not having too great success with it.


First off, it will not work with 2.4ghz


Secondly, when connected up to 40mhz, it works ok, if quietly, until I connect a servo into the rx. Then, when operating the servo the unit suffers with a lot of crackling interference.


Has anyone else experienced this? Or have I got a duff unit?


Thanks in advance


Ian
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Stan

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Re: JJC sound unit
« Reply #1 on: April 04, 2016, 07:20:25 PM »

Hi Ian  pm sent.

Stan
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boatmadman

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Re: JJC sound unit
« Reply #2 on: April 04, 2016, 07:57:24 PM »

Stan.
Reply pm sent
Ian
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microgyros

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Re: JJC sound unit
« Reply #3 on: April 04, 2016, 09:04:17 PM »

Having acquired an old jjc sound unit, the v8 one, I am not having too great success with it.


First off, it will not work with 2.4ghz

The difference is the faster frame repetition rate on 2.4 GHz. That rate differs between brands and some receivers have the option of changing to a slower rate to work with older analogue servos. A 7ms "multi copter" setting is bound to show compatibility issues with older and aftermarket designs hooked up to those 2.4GHz receivers
Quote
Secondly, when connected up to 40mhz, it works ok, if quietly, until I connect a servo into the rx. Then, when operating the servo the unit suffers with a lot of crackling interference.


Has anyone else experienced this? Or have I got a duff unit?
You possibly need a lower ohm speaker with amplifier.
It is most likely the design and installation and unlikely to be a quality control issue.
That is a known problem with amplified sound systems. It can be picked up by unwanted coupling to amplifier input or poorsupply decoupling. It can usually be sorted by smoothing the supply of the sound unit (separate supply, regulated bec supply, power supply capacitors) Details of your installation would be needed to specify the easiest way.
Quote


Thanks in advance


Ian
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Umi_Ryuzuki

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Re: JJC sound unit
« Reply #4 on: April 04, 2016, 09:55:04 PM »

The original first run designs worked well with 2.4ghz.
I did an entire JJC diesel sound and smoke unit install in a Tito Neri back in 2006.
Everything preformed flawlessly, and we were using a Spektrum DX6 at the time.


Second generation units developed a skip, and no one could get any sympathy regarding a fix.
Buyers were told they were being too sensitive about the sound cycle. However, I had purchased one of the original units for myself, and a second unit two years later, and when
I hooked each one up to the same radio, and same power and speaker out put, the newer
unit would heavily skip at full throttle.
Unfortunatley, I can't speak to what might be the issue with your JJC sound unit, unless you
managed to get a SLAVE unit, and are trying to run it unamplified without the master unit.


You did say that you have the V8 master unit, so it might be one of the POTs on the board need adjustment for volume. Facing the POTs, the right, outermost POT should adjust volume.Not sure why you might be getting interference.
 :-)

boatmadman

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Re: JJC sound unit
« Reply #5 on: April 04, 2016, 09:59:41 PM »

Thanks Micro Gyros and Umi for your response.


The set up I am trying to make work is a PE311 proportional slave, running with a 40w amplifier to a 6 ohm speaker. Power is 3s lipo, rx power from a 4 x AA cell pack.


I have tried adjustment on both the pots on the unit without improvement.
Ian
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microgyros

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Re: JJC sound unit
« Reply #6 on: April 04, 2016, 10:23:33 PM »

Spektrum DX6 would be 11ms frame and I can't help wondering if it is the same sort of frame related issue that Umi described on 2ndgen unit.
  If you could only see an oscilloscope trace of the receiver power supply rail when a servo moves. It would improve tenfold with either 1,000 microfarad capacitor or supplied by a 5v bec. Can this sound unit derive its power from elsewhere?
   6 ohm seems a rather high impedance speaker if you have a 40 watt amplifier. Eight ohm would suit a pre-amplifier chip of the type found on a sound circuit that can be buffered by an amplifier. An amp lets you use a lower impedance speaker or a higher voltage supply.
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boatmadman

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Re: JJC sound unit
« Reply #7 on: April 04, 2016, 10:44:42 PM »

Sorry I didn't make it clear but the 3s lipo supplies the jjc only.
What impedance speaker would you suggest?
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microgyros

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Re: JJC sound unit
« Reply #8 on: April 05, 2016, 12:02:24 AM »

You should be able to make a racket with a physically large 8 ohm speaker on 12volt. It may be no good on a pond, at a distance, so I presume that's why you have a 40 watt amp. I am not up to doing the calculations at this time but there is a maximum power a certain speaker resistance can deliver on 3s clipping occurs Are you sure it isn't 16 ohm with one obscured? Have you got another speaker and what is the lowest the amplifier can take on 12volt?
Does the volume control on the sound generator board have no effect at all?

  That power arrangement certainly makes more sense to me. Is nothing of the JJC board actually connected to a red servo cable?
If you have a long feed wire from the 3s Lipo, have a bad connection or share the 3s with another load, or are actually using a bench power supply, a large enough 16 volt electrolytic capacitor close to the JJC +/- 12v will stop any supply borne noise . If it is not stopped by smoothing that supply then a high gain amp or preamp is picking up and amplifying electrical noise. That is not such an easy thing to sort without seeing it, unless you hear Radio Moscow. There is no point in blindly taking guess measures like r.f. shielding or adding bypass capacitors without first knowing if they are appropriate.
 One last very long shot. Is the amplifier d.c. coupled to the speaker or is there a large capacitor?
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Stan

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Re: JJC sound unit
« Reply #9 on: April 05, 2016, 08:27:57 AM »

HI Ian the slave unit took its power from the master unit also feed back the sound to the master unit. JJC supplied  a master amp for use with slave unit but like I said last night it was not the best. The cable that connected the  master and slave  carried power and sound  so you will need to supply both power and feed back sound to an external amp this may prove difficult. Contact  the chap I told you about he may be able to help .

Stan.
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boatmadman

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Re: JJC sound unit
« Reply #10 on: April 05, 2016, 08:48:05 PM »

Here are a couple of photos to show the set up:
Ian
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Umi_Ryuzuki

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Re: JJC sound unit
« Reply #11 on: April 06, 2016, 12:56:34 AM »

So you are just trying to run the Slave unit, no master unit is available?


http://www.modelboatmayhem.co.uk/forum/index.php/topic,53379.msg549984.html#msg549984



microgyros

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Re: JJC sound unit
« Reply #12 on: April 06, 2016, 04:25:12 AM »

Here are a couple of photos to show the set up:
Ian
I can barely make the pictures out but the speaker looks big enough. A 4 inch, 8 ohm mylar cone will burst your ear drums if you try. You can loose the large capacitor soldered to the speaker.
  As for the crackling, that would normally be sorted by either a power line capacitor on the JJC board or a better interconnection between that and the amplifier. Only someone with them on the bench can find out why the servo affects the sound. The photo shows a 3-wire servo-plug connection from JJC to the receiver and that is pretty relevant unless red is unconnected on the JJC board.
  One last thing, someone with them and the test components will be able to show whether the 2.4GHz problem is due to the faster frame rate or that the JJC needs high amplitude servo pulses.
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Dave Cook

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Re: JJC sound unit
« Reply #13 on: April 06, 2016, 05:28:27 PM »

Hi , pm sent to you and Stan , I had the same issues but there is a solution .
Best Regards Dave
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Dave Cook

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Re: JJC sound unit
« Reply #14 on: April 11, 2016, 06:31:10 PM »

Hi Ian , Got the diagram , please ring me anytime before 6pm , before i post it.
Dave :-))
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