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Thread: L-Tronics LP-1

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    Default L-Tronics LP-1

    Does anybody here know much about these? It is on the correct frequency, which is 154.785 MHz, but I want to get the Tone A and Tone B changed. I think L-Trronics is out of business. I don't have proper equipment to change it. Does anybody here have any idea where I can go to get this done? L-Tronics LP-1.jpg


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    Looks old. Is it even synthesized? I suspect tone reeds of some type.

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    Default L-Tronics LP-1

    Quote Originally Posted by Notarola View Post
    Looks old. Is it even synthesized? I suspect tone reeds of some type.

    You are correct. It IS old and NOT synthesized. I believe it uses a crystal.

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    Inside photo would be helpful.
    "Lets at least get some speed! Lets get to a hundred!" -J. Dewitte

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    Crystal for RF = tone reeds unless you are super lucky and its a tunable circuit for the tone decode. As d119 said a internal picture would be a great help.

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    Default L-Tronics LP-1

    Here is what it looks like inside.
    Attached Images Attached Images

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    WHAT in the HELL is that GI SPO256 doing in there? Does this thing have synthesized speech? That is FREAKIN AWESOME! Please put my name on this device should they decide to get rid of it.

    The two pots labeled "F!" and "F2" on the board marked "PAGING DECODER" is unquestionably your tone frequency adjust. Now exactly how that is accomplished is beyond me without documentation, but I would guess it is done by the following method:

    1. Inject a signal into the unit with desired Tone 1.
    2. Monitor test point and adjust F1 pot until test point shows Tone 1 detected.
    3. Repeat for Tone 2 using F2 pot.

    What a nifty device. I notice the receiver is made by Regency.
    "Lets at least get some speed! Lets get to a hundred!" -J. Dewitte

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    I will send you a PM.

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    Thanks, I got it. I'll let you know. Probably not much.

    Does it in fact have synthesized speech? What does that do?
    "Lets at least get some speed! Lets get to a hundred!" -J. Dewitte

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    Yes the pots control the the decode freq. Real easy to adjust with a audio freq counter.

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    Default L-Tronics LP-1

    I am going to try and find someone to do his for me. So, they will need an:

    -Audio Frequency Counter, and

    -A Signal Generator

    Is that it or is there anything else I need to line up?

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    Still wonder what the speech synthesis is for?
    "Lets at least get some speed! Lets get to a hundred!" -J. Dewitte

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    You should probably get someone with a service monitor that can generate the two tone sequence at a reasonably weak signal strength to make sure
    the tones are decoded correctly.

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    Looks like a reworked Regency ACT C1W weather receiver. Perhaps the speech IC was used for the original application as a weather alert receiver.

    s-l1600.jpg

    s-l1601.jpg

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    Nothing I can find about either unit mentions speech. Perhaps I'm misreading the chip number, or it's being used for the alert tone only.
    "Lets at least get some speed! Lets get to a hundred!" -J. Dewitte

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    I think your misreading the chip. Voice synthesis would be a very expensive item back in the TTL days. If they could add that then using a couple of OP amps as a resonate circuit is out of sync with the rest of the unit.

    Tone alignmet can be done by using one of several sound card tone generator apps and injecting the audio at the audio in point. You dont need to worry about RF as your just triggering the decoder. A scope or even a voltmeter should show you wen you hit the right tone. NOTE: you may have to try various pins to find the correct one to measure for decoding. There are also some good sound card scope programs.

    Having said that it would still be best to do it in a radio service facility. Being that old the Xtal may have drifted as well as the general alignment

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    The two 28 pin chips each with crystal oscillators are pretty much out of place in conjunction with a simple alert decoder that apparently uses two 567 PLL's. That whole circuit could have its logic performed in a few gates. Can Jim get a closeup of those chips without wires blocking the part numbers?

    I have a suggestion. It could be one of those alert decoders to tell folks in cold places that the school bus has arrived. The bus sends out a short transmission when it stops, the receiver might make a voice announcement.

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    Ugg Thanks RFI. If I had bothered to read the chip number clearly seen in the picture... Anyway monitor pin 8 of the 567. Ot will go low on decoding the correct tome. Inject your desired tone at pin 3 slowly adjust the variable resistor until pin 8 goes low. For best accuracy drop the input tone level and tweak the resistor for best position.

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    Jim -

    What is the part number of the GI chip in this unit and the chip next to it please?
    "Lets at least get some speed! Lets get to a hundred!" -J. Dewitte

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    Inquiring minds want to know what that monitor will say once it is triggered;

    It could be:
    The school bus has arrived or

    the nuclear plant is melting down please depart at your earliest convenience.