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The ebay 3 dollar FM radio receiver..

Today the 2 ebay 2$69 FM radios arrived (free shipping fomr China via Switserland duh). both worked, but a bit sensitive to movement... ebay item 160784342887

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As I wanted to use these cases for geiger counters, I opened one:

Lots of parts for 2$69:

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A close up of the board:

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here already you see a switch that is not mounted (soldered) in the correct vertical position. Very long leads on the capacitors, no SMDs.

How can this receive? Well, there is a chip on the bottom:

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Also the large inductor at the battery terminal sort of isolates the earphone leads so those are used as antenna. There is a reset button to go back to 88 MHz, and then each press of the 'scan' button takes you to the next station. The earphones seem to be 2 34 Ohm in parallel, measure 17 Ohm, on one channel of the stereo plug, the other channel is used on/off switch in the earphone lead... So mono it is.

Do you see the bad solder joint on the right to the piece of paper, that actually is one end of a 10 uF capacitor that is not soldered at all. Under the piece of paper was an other bad joint, a broken solder track to one of the transistors.

PCB is flimsy, track just peel of, Earphone and sound quality is not bad at all....

Dunno what chip this is, it says 1980 (year???), on it, and you can see the code under that:

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All in all a rather complete thing, now that I fixed it it works OK.

Will not be easy to get the geiger counter HV generator, tube, and PIC in it. transformer is JUST too big... could cut the plastic of the transformer.

Reply to
Jan Panteltje
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That is interesting. I received some stuff from China which was routed through Switserland. Perhaps some tax evasion scheme? Switserland's VAT is 8% instead of the usual 20% in other European countries.

--
Failure does not prove something is impossible, failure simply 
indicates you are not using the right tools... 
nico@nctdevpuntnl (punt=.) 
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Reply to
Nico Coesel

Hi Jan Where are you getting your power supply circuit? Take a look at techlib.com. He uses an audio transformer to get 500 volts. Curious, which Geiger tube are you using? JB

Reply to
haiticare2011

I received (Canada) a brochure from Pasternack (California) with a Swiss postmark! I wonder if the Swiss have the cheapest postal rates in the world?

Reply to
Wond

On a sunny day (Fri, 24 Jan 2014 08:26:33 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :

Hi, I already use this design with a PIC:

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Then I did the audio transformer thing with a 1:10 transformer, the one I want to use, and a 3.4 V LiIon battery, running from that same PIC PWM output:

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I ordered the last??? SI-29BG GM tube from ebay... ebay item 190928106922

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only about 7 cm long, and that won't fit in this radio box either, but maybe the socket can come of?? Was only shipped recently, the guy was on holiday, so I have not got it yet [1]. So, anyways, except for size, everything has already been working, gm_pic for years.

My second option is a solar powered flashlight to fit it in: ebay item 370856410707

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Solar powered geiger counter, cool thing when the world, and electrickity, has ended and you need to check your veggies...

This tube, the SI-29BG if I understand the specs correctly, should be a lot more sensitive than the SBM20.

[1] Will of course first try it on gm_pic.

The transformer is from conrad, I can look up the number if you need it.

Reply to
Jan Panteltje

Jan Panteltje schrieb:

[...]

Maybe something like TDA7021T; as to the pin count it's identical.

HTH

Reinhard

Reply to
Reinhard Zwirner

On a sunny day (Fri, 24 Jan 2014 18:50:18 +0100) it happened Reinhard Zwirner wrote in :

I have looked at that datasheet, and some others like TDA7010.pdf, but this thing runs on a 1.2 V rechargable.. That TDA needs 1.8 V to 6 V. Also this thing has a frequency scan input.

Very strange, my solar powered flashlight radio just came in, and exactly the same controls, one reset (to ~80 MHz), and one scan button (to the next station).

Will open it later... ebay item 370856410707

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man that one works great, good sensitivity.

A whole lot of ee-bay stuff came in today (in the evening!), OLED display too, need to test a driver I wrote for that, gonna be a busy weekend ;-)

Reply to
Jan Panteltje

Jan Panteltje schrieb:

[...]

Okay, it looks more like a clone of TDA 7088.

Bye

Reinhard

Reply to
Reinhard Zwirner

When you get this thing working satisfactorily, Jan, are you going to make the final schematic and build notes available so others can follow up on your idea? I personally am more than a bit concerned about tinned tuna. It's bad enough having mercury in it let alone radio-activity.

Reply to
Cursitor Doom

On a sunny day (Fri, 24 Jan 2014 19:37:59 +0100) it happened Reinhard Zwirner wrote in :

Found it, see also my other posting on the solar powered flashlight, same chip, it is a HX1618, dataheet (Chinese) here:

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see page 3 or 4 for circuit diagram.

Reply to
Jan Panteltje

On a sunny day (Fri, 24 Jan 2014 18:44:38 +0000 (UTC)) it happened Cursitor Doom wrote in :

Sure, pacifc ocean fish from near Fuckupshima can proabably be used for room lighting.. Yes I will make a website.

Reply to
Jan Panteltje

Jan Panteltje schrieb:

[...]

Not bad!

Thanks for info

Reinhard

Reply to
Reinhard Zwirner

It's difficult to get analog circuits working down to 1.0V. The transistors, inductor, and unusually large capacitor appear to be a power inverter.

Reply to
Kevin McMurtrie

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