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 Post subject: Long time headache for a tone/radioteletype decoder display
PostPosted: Sun Sep 25, 2011 7:49 am 
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Location: Mideast USA
Hi all. This will not be easy... This is lost but not found :sad:

Many years ago, I built a circuit for I do not remember what for :sad: :???: :cry:

It worked very well, removed its only 14 pin IC from it as I needed it for something else and now cannot remember what the IC was :mad:

Checked all ICs used in other projects for compatibility and cannot match what it was. :x

Takes audio input on pins 8 & 10
+Voltage is on pin 14, probably +12
Gnd is on pin 7
It has a potentiometer on an RC circuit on pins 5 & 6 as to tune to the audio fed. <--- corrected

The outputs are 2 LEDS in counterparallel between pins 3 & 4;
Same for pins 12 &13, another pair of counterparallel LEDs
That clued me there is AC or inverted pairs of levels outputted that turn both leds pairs

Sort of remembering the LEDS flash when correct tones or pair of tones are present, as in a RTTY tuning indicator.

It is not:
558
14551
7414
4053
556
7556
LM339
567
CD22204
MC1374
3900
7404
XR2206
XR2211
565
4030
AD650
CA3179
7408

Clues, please ? Any dual PLL in 14 pin ?
Miguel :sad:

Edited: added ---> http://s588.photobucket.com/albums/ss32 ... CF0035.jpg
Image



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Sun Sep 25, 2011 8:11 am 
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Sure sounds like a dual PLL, but could it be a dual opamp?



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Sun Sep 25, 2011 8:30 am 
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Thanks, Len.
Twisted my brain in all directions; cannot think what it was, a dual, a quad op-amp; checked maaaaany things.... :sad:
Only remember it worked well. What a brain twister doing reverse design when memory is not collaborating.

The original post has been edited now; added a picture of the contraption.

Miguel



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Sun Sep 25, 2011 1:32 pm 
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First, can you explain exactly what it is that this does. I understand it must be some frequency determining indicator for rtty tuning.
Was this a published circuit or something you designed, and how long ago?
Did you buy from locals, like radio Shack or did you have access to industry wide components?
Tell us all you know!

Externet wrote:
It has a potentiometer on a RC circuit as to tune to the audio fed to pins 5 & 6.
So the audio goes to pin 8 through the resistor string and the 10uf to pin 6?
Externet wrote:
It has a potentiometer on a RC circuit as to tune to the audio fed to pins 5 & 6.
Does it tune an oscillator is is it something like a filter?
Some possibilities:
Look into the 4xxx series. Some use pin14 power, 7 ground and pins 2, 3, are outputs.
Quad op amps? PLL's? (most do not use pin 14 as Vcc)

Hummm... THE PLOT THICKENS!

Len



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Sun Sep 25, 2011 2:17 pm 
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Wrote an improperly structured sentence
Externet wrote:
...It has a potentiometer on a RC circuit as to tune to the audio fed to pins 5 & 6. ...
Which should had been :

It has a potentiometer on an RC circuit on pins 5 & 6 as to tune to the audio fed.

I will try to edit the original post if can. ----> Yes, I was able to <---- edited

- Not a published circuit that I know, not bought as kit,
- I designed the application ~10 years ago probably reading its data sheet.
- Sorry, cannot explain exactly what it does. Barely remember feeding audio and tuning the trimpot for the leds to light up :sad:
- Industry components.
- Cannot remember if it tunes an internal oscillator(s) or a filter(s) :cry:
- Yes, audio is fed to pins 8 & 10; probably for two internal separate circuits to detect the high and the low tones and flash one pair of leds on one and another pair of leds the other tone.
- Most of those resistors should be feedback gains and coarse frequency ranges. The way they are drawn appears to be in an audio string but not.

What a hard thing !
Thanks Len
Miguel



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Tue Oct 11, 2011 3:35 pm 
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And, so is this thread kaput! Did everyone quit?



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Tue Oct 11, 2011 5:15 pm 
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Location: Phoenixville, PA USA
Looks like a quad opamp to me. The right side opamps (@ input) looks like signal
conditioning up to the forward conduction of the LED's, probably to make it turn
into a square wave, then fed through the 10uF to the left side where the other
2 opamps look like they are comparators, maybe? Or are they just frequency
selective where the output of amp 4,5,6 (oscillating with input?) is fed back to
pin 1 to cancel out those frequencies to create a beat frequency?

That's my quick take on it. I think it's a quad opamp. Anyone else? Anyone up
to a simulation? Mine is out of commission until I can get the Win7Pro upgrade.

CeaSaR



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Thu Oct 13, 2011 6:27 am 
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That is great! suggestion, CeaSar.

Using a simulator and trying several library chips on it hoping to achieve the expected result. *

Almost sure, pins 3&4 and 12&13 are either
- balanced op amp outputs
- or individual non-inverted and inverted comparator outputs;

In such way that one of the led pair is lit for a particular frequency
and one of the other led pair is lit for another frequency

I do remember both of each led pair appear to light up as the frequency is high enough taking turns every cycle.
When properly tuned, both pairs appear lit.

As probably in AFSK / RTTY tuning.

The 100K pot tunes either-
- the frequency difference between tones,
- or their centre frequency.

* I tried to find which 14 pin chip would have + at 14 and gnd at 7; many do, no problem there.
but unable to find which have 3&4 and 12&13 as individual opamp or comparator outputs.
Yes, could be a quad something.

Two frequency-to-voltage circuits using a quad comparator IC comes to possibility...
Thanks for playing this mindtwister quiz.

Miguel



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Wed May 01, 2013 2:35 pm 
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Location: Vancouver, BC
Hi Miguel. This is a bit late, but it's the first time I've seen this thread.

My bet is that the IC is a 4000B series CMOS logic hex inverter with sections of it used as linear inverting amplifiers. First clue is the power/ground terminal arrangement.

I've used these in my design for R/C speed controller a long time ago....

Either a 4069B, or the heavier duty 4049B?

Edit May 2: After further analysis, it does look like a B series CMOS hex inverter with all 6 sections used as inverting op amps. The circuit has no input, only an output. It has an adjustable frequency oscillator. Two sections are in parallel and used to buffer (lower the impedance of) the output. Possibly it was used as an audio oscillator or a BFO?



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 Post subject: Re: Long time headache for a tone/radioteletype decoder disp
PostPosted: Thu May 02, 2013 9:57 am 
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It's never late.
Thanks, Bob.
Will investigate what series 4000 could I have used there, and digest your suggestions. It is obsessive now. It does have input, highly probably audio into pins 8 & 10.
Output was -this for sure-, the counter paralleled leds pairs as indication only.

BFO does not ring enough bells, but a possibility.
Detecting AFSK -audio frequency shift pair- has more chance to be; to fine tune a radio receiver properly. Two leds for one frequency, two others for the other frequency. When all four leds lit, audio frequency pairs is valid to decode into a text readout.

Or, DTMF IC without crystal?

The :? part is there has to be AC at the output pins for both leds to light up.

Miguel



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