Installing small speaker inside FTA receiver

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polgyver

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Recently I converted older computer LCD monitor to video display by adding to it an inexpensive Video-to-VGA converter (e-bay, $ 22). I started using it as a display with FTA receiver, when pointing dishes. However, the sound was missing. So I installed a small speaker inside the receiver (luckily, it was a lot of room for it). Pictures follow

IMG_3447.JPG IMG_3448.JPG IMG_3452.JPG IMG_3453.JPG
 

turbosat

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Neat! When I saw the thread title, I wondered "Why do that? " lol
I noticed awhile back those little speakers are getting hard to find, so now whenever I find one in something that's hopelessly broken, I salvage it for laer use.
 

polgyver

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Does the line-level audio output have enough power to drive a speaker without an audio amplifier?
This particular receiver (Captive Works 600 Premium) has pretty high output level, however, some other receivers could be "weaker". First, I tried to use outside speaker 32 Ohms, it worked fine. Next, tried 8 Ohm - also fine. But I did not have small speaker with higher resistance, so I used one with 3.2 Ohm - but added 10 Ohm resistor in series (visible on photos). Even with this limitation, the audio could be heard pretty well.
 

Anole

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three variations

One of my early computer LCD monitors, had speakers inside.
Took line input levels from the computer sound card.

To get a bit better match to the speaker, ya might be able to salvage a matching transformer out of an old transistor radio (if anyone even remembers what those are).
Something with a 1000 ohm to 8 or 4 ohm output transformer would be a better match to the line output (which if I recall, is more like 1000 ohms).

Many years ago, Radio Shack had a Sanyo (?) power amplifier chip for about $2.
I think it ran on 12 volts, took line input, and fed a speaker directly.
It ran a watt or two. Made a great poor-man's amplifier for a hi-fi tuner I had.
 

polgyver

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Seems this CW has line output much stronger than 1000 Ohm. Few weeks ago I tuned in to some exotic TV on 97, which ran a steady display and a sound (probably 400 Hz), I loaded the output with 1000 Ohm potentiometer and AC voltmeter, and to get to half voltage reading, I had to lower the resistance to some 15 ohms. Looks that it was designed to drive also earphones. Cheers, polg
 

polgyver

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Neat! When I saw the thread title, I wondered "Why do that? " lol

It offers some battery saving convenience when installing a dish in a place without power or if the power source is far away. Typically, a receiver with small TV is powered from portable battery and inverter, just under the dish. With pre-programmed receiver equipped with speaker, one can scan the sky with the small TV off, and no need to glance at the screen, just listen for the audio. When sat is found, the small TV can be switched on just for a minute to tweak and max the dish. Of course, headphones could be used, or, small external speaker, but this would be another item to carry and/or keep.
 

eurosport

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polgyver said:
This particular receiver (Captive Works 600 Premium) has pretty high output level, however, some other receivers could be "weaker". First, I tried to use outside speaker 32 Ohms, it worked fine. Next, tried 8 Ohm - also fine. But I did not have small speaker with higher resistance, so I used one with 3.2 Ohm - but added 10 Ohm resistor in series (visible on photos). Even with this limitation, the audio could be heard pretty well.

Cool!

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eurosport

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Pixl said:
Euro,

That is the worst avatar you have ever used. Ugg.
Put the babes back up!

I'll change it when I get home from work. LOL

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polgyver

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The LM386 or LM380 would make a nice little audio amp inside... with the LM386 giving a 1/2 W and the LM380 up to 5W.

That's true, but for me (and, possibly, other tinkerers) simplicity is the key. For this receiver, Captive Works 600 S, the audio output is rather high. Even when losing 75 % power on 10 Ohm resistor, the reminder, 25 % is loud enough to hear the audio. Of course, with speaker 8 Ohm, it would be louder. Please, note that I installed this small speaker without drilling anything nor using bolts. I just used a slice of swimming pool "noodle" and double-sided mounting glue tape, plus soldered wire. Maybe I could skip the resistor, but I felt that this could sort of "overload" the audio output. Cheers, polgyver
 
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