Help with this Stereo Encoder NJM2035

[Electrojosh86]

First off I am not sure if this is in the right section but I am going to ask my question and see if I can get some help from here anyways. I came across this circuit and decided to use it in in an FM transmitter I was building. Though it does work as there is stereo sound there is an rather high pitched undertone kinda sounding like an ongoing "ping" sound the rotates from left to right and back to left over and over again. Not sure what it is and since I am rather a beginner and have not built up an impressive collection of tools like an O-scope I cannot really figure it out without just jumping in and experimenting. Thus why I am here asking for you fine folks help. If someone can help improve on this schematic then please do so. Thanks!

http://www.next.gr/audio/Stereo-Circuits/HI-FI-Stereo-Encoder-Multiplexer-l5705.html

Oh, and I have tried multiple IC's and the same discrepancy follows.

 

[crutschow]

Perhaps the crystal frequency is off. Do you have another crystal you can try?

 

[Electrojosh86]

No I do not, I only had 2 on hand and the leads on one broke. It could be off now to think of it. I did get it off eBay from some china store and I was looking at it and didn't see any markings.. not good. I need to find a reputable place to buy this crystal if it turns out to be fake.

 

[Audioguru]

Why didn't you look at the datasheet from the manufacturer of the NJM2035??
It shows a recommended circuit that adds very important filters and explains in Japlish that the 19kHz pilot tone is a squarewave and an LC tuned circuit converts it to a sinewave so that the 3rd harmonic of the squarewave does not beat with the subcarrier. They say the harmonic is dangerous (deadly?) but I say it causes the whistles you hear.

 

[Electrojosh86]

Japlish? Is this a real language. Yes, after I asked my question I went back to the data sheet and saw that. If I can get my hands on the 5 and 20mH variable I'll run with that. Also, realized that my transmitter was missing a cap and that was causing all kinds of noise as well. So, now it's cleared up a bit but that tone is still there.

- - - Updated - - -

http://radiohobbystore.forumisrael.net/t10-stereo-coder-for-fm-transmitter-on-njm2035

Is a diagram I found that is clearer than the data sheet to read. The only thing I want to know is; where to get the 5mH and 20mH variable inductor. In the picture they look like IF CAN transformers like found in vintage radios.

 

[Audioguru]

Japlish? Is this a real language?

I worked for a Japanese audio manufacturer. Everything was originally written in Japanese then a guy who could hardly speak English translated it into Japlish.
My son married a girl from Mexico who could not speak English. They speak together in Spanglish.

....but that tone is still there.

Since the tone rotates from left to right and back to left over and over again then I think that is what happens when the 38kHz crystal is not exactly 38.0kHz. E-bay junk from China.

 

[Electrojosh86]

I figured that the crystal might not be authentic. It actually is not the first time I got something from eBay that was a component and it turned out to be false. The fact that there is no markings on the xtal should have been a dead giveaway. I found a canadian electronics store on eBay that sells them and the pics shown actually have values on them. Still, that doesn't mean anything. Now, where to find the instructors?

 

[Electrojosh86]

In this circuit is it possible to substitute the instructors (5mH and 20mH) for smaller instructors just with different capacitors in the tank circuits to match the frequencies given? I know math says it can be done but wanted to know if those values were chosen by something else.

 

[Audioguru]

I have never seen an instructor that was dead and wound with wire.
I have never seen an inductor that taught in a university.

 

[Electrojosh86]

autocorrect got me. Typing fast on my phone..