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Thread: beat amplifier

  1. #1
    Registered user. CORKPJ's Avatar
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    Default beat amplifier

    I needed a beat amplifier for a 400 day clock repair. A small stick FM radio receiver has all the requirements, but needs slight modification.
    Open the case and remove the pickup coil and associated diode.(the bits with wax on them). Make room for the 3.2m/m socket connection for the piezo diaphragm input, if there is none. Connect the centre connection of the piezo diaphragm to the base input of the transistors that drive the headphones. The other connection to the battery negative. The piezo diaphragm can be hung or clipped to the movement just about anywhere. Its very sensative. The better the quality of earphones, the better the sound.image shows the setup. Its easy to construct and very useful.
    Attached Thumbnails Attached Thumbnails beatamplifier 008.jpg  

  2. #2
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    Thumbs up Re: beat amplifier (RE: CORKPJ)

    That's what I would call " Aussie ingenuity". Well done.




    leghorn

  3. #3
    Registered User Scottie-TX's Avatar
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    Default Re: beat amplifier (RE: leghorn)

    I made mine using an electret mike element and inexpensive 9V. mini amp and alligator clip.

  4. #4

    Default Re: beat amplifier (RE: CORKPJ)

    I feel kind of silly in giving this information out since almost everyone here knows more about clock repair than I do. I wanted a beat amplifier because my shop is in the basement along with the laundry, etc. The noise made it difficult to hear the beat of clocks. I picked up a mechanics stethoscope at Harbor Freight for a special price of $1.99. I can hear every tick and tock and all the other little noises clocks make.
    Dave

  5. #5
    Forums Administrator harold bain's Avatar
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    Default Re: beat amplifier (RE: Dave D)

    Dave, I also use a mechanic's stethoscope. Works for me
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  6. #6
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    Default Re: beat amplifier (RE: Scottie-TX)

    Quote Originally Posted by Scottie-TX View Post
    I made mine using an electret mike element and inexpensive 9V. mini amp and alligator clip.

    Scottie: The pickup for amplifier I bought from Time Savers died. Can you tell me where you bought the element you have? Thanks...Paul

  7. #7
    Registered User Scottie-TX's Avatar
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    Default Re: beat amplifier (RE: Paul Arsenault)

    I do note that TIME$AVERS does sell the pickup a$$embly alone but asks a ridiculous $21. for it. Check yours out or if you know a friend who does electronics - have him do it. In all probability, a wire is simply broken either at the plug end or pickup end - more likely broken at the plug end. However I bought my electret mike element from Radio Shack for a few bucks.

  8. #8

    Default Re: beat amplifier (RE: CORKPJ)

    Quote Originally Posted by CORKPJ View Post
    I needed a beat amplifier for a 400 day clock repair. A small stick FM radio receiver has all the requirements, but needs slight modification.
    Open the case and remove the pickup coil and associated diode.(the bits with wax on them). Make room for the 3.2m/m socket connection for the piezo diaphragm input, if there is none. Connect the centre connection of the piezo diaphragm to the base input of the transistors that drive the headphones. The other connection to the battery negative. The piezo diaphragm can be hung or clipped to the movement just about anywhere. Its very sensative. The better the quality of earphones, the better the sound.image shows the setup. Its easy to construct and very useful.
    Howzabout more pics, and maybe a diagram, for us electronically ingnernt folks?

    bangster
    1. Check out the REPAIR HINTS & HOW-TO's forum! Click Here.

  9. #9
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    Default Re: beat amplifier (RE: bangster)

    I bought a piezo transducer from Radio Shack for $1.99, soldered it to the jack to the amplifier and it works perfect. In fact it's alot more sensitive than the original unit.

  10. #10

    Default Re: beat amplifier (RE: Paul Arsenault)

    Quote Originally Posted by Paul Arsenault View Post
    I bought a piezo transducer from Radio Shack for $1.99, soldered it to the jack to the amplifier and it works perfect. In fact it's alot more sensitive than the original unit.
    Yeah, but Cork's unit starts out life as an fm radio, and those don't normally come with input jacks to plug the piezo into. That's why he does some modifications to get the input. He says:

    "... remove the pickup coil and associated diode.(the bits with wax on them). Make room for the 3.2m/m socket connection for the piezo diaphragm input, if there is none. Connect the centre connection of the piezo diaphragm to the base input of the transistors that drive the headphones. The other connection to the battery negative."

    Without further guidance, I won't know a pickup coil & diode from a watermelon; and I don't know enough about transistors to tell which is the base input. But with just a LITTLE more of the right info, I think I could follow the instructions.

    bangster
    1. Check out the REPAIR HINTS & HOW-TO's forum! Click Here.

  11. #11
    Registered User Scottie-TX's Avatar
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    Default Re: beat amplifier (RE: bangster)

    Well, I also was trying to suss it out. I gather that he inserted his pickup at the audio preamp input. Since it has no speaker, it also has no power amplifier, so this beat amp will require an ear bud or similar. Not sure about the "pickup" he removed, nor the diode. Possibly the "pickup" was the second interstage transformer. Perhaps the diode was it's second detector. If I were doing this, I'd probably choose a cheap radio that does have a power amp and speaker. Then no headgear is required.
    As for P/Us and diodes vis a vis watermelons - you'll notice the diffrunts right away. Watermelons are juicier. Diodes are hard to chew and coils get stuck between yer teeth, plus neither have pits to launch.

  12. #12
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    Default Re: beat amplifier (RE: Scottie-TX)

    Scottie: If you have a stereo with a low level input you can plug the Radio Shack pickup directly into it and it works fine. No seeds no juice and no mess. Paul
    Last edited by Paul Arsenault; 12-19-2008 at 08:25 PM.

  13. #13
    Registered User Scottie-TX's Avatar
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    Default Re: beat amplifier (RE: Paul Arsenault)

    Oh, I understand that, PAUL. A phono input would work just fine because it has a pre-pre amp. Might be a tad inconvenient, wheeling a forty pound McIntosh pre amp and sixty pound, HH Scott power amp around for beet testing tho. But yeah; Understand. Me an' BONG wuz jes figgerin' out what CORKY had goin' on there.

  14. #14
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    Default Re: beat amplifier (RE: Scottie-TX)

    Scottie: HH Scott, Maynard Mass. In it day that was good stuff. Now that is some vintage equipment. Is it one of the tube type? Brings back memories. Paul

  15. #15
    Registered User Scottie-TX's Avatar
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    Default Re: beat amplifier (RE: Paul Arsenault)

    Mc is C32 - top of line ca. 1975. HH Scott top of the line LK 150 laboratory series Ca. 1958. Now running four, KT88s. These wake up a pair of Altec Mod 19s - home version A7 VOTs with 21" horns I added.
    Whatta beat amplifier!

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