7 Transistor AM Radio Kit
 

Anyone try building one of those $8 China AM radio kits?

I ended up purchasing one off fleabay, it was eight dollars including shipping from China!

The instructions were in Chinese, I had to figure out the symbols for the color coded IF transformers.. But that was easy enough, as they had them listed for the resistor color code.

Once assembled, it worked great and was a lot of fun to build.. The last one I built was in 1974.. It was an Archer Kit from Radio Shack, and it cost $10 then!

Basically, this is the same thing as the 70's Japanese kit. Only, it runs off 3v instead of 9.

eBay link?

Will do!

http://www.ebay.com/itm/The-radio-su...item1c42d64397

And another:


http://www.ebay.com/itm/DIY-Kits-Sup...item19f754bf02

Thanks man, I ordered one... looks like a fun little project.

Neato !

Here is an AM/FM one, but it uses IC chips....

http://www.ebay.com/itm/New-AM-FM-AM...p/310930976499

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Back in 08' (I was still in high-school then) my college had me make a kit radio as part of a summer 'enrollment enticement' course. It was an AM-FM transistor affair with no case.

When I took electronics in 1970 they had us build a small AA5 tube radio from a kit. It was point to point wired and we had to completely assembly it with no solder and to get a passing grade it had to work. The idea was to teach good mechanical connections.
After that was done we soldered them up and the instruction then inspected our soldering job.

Gregb

The Radio Shack kits were still around in the early 90s when I was a kid. They may have been different though; plastic sides, the rest of it cardboard and springs for solderless connections. I built two AM/short wave units; both quit in short order. I'd like to know what I did wrong, if anything. Then of course there was the crystal radio that didn't come with enough wire to make a proper tuning coil. It limped along anyway, and was totally awesome to me back then.

I built the AM-FM one with the surface mount chip.. Not a great performer, but fun to build anyway.

Yeah I was tempted by FM but thought a superheterodyne would be more fun. This will be a good radio to throw into my travel bag, I always like checking out what's going on, on foreign airwaves.

Most all FM sets old enough to be knob tuned ARE superhetrodyne type receivers only with a different detector circuit.

If you want a good radio for air travel, and foreign lands look for a good AM-FM-LW-SW portable...Something Like a Sony (some will also tune the Japanese FM band), Grunding, Sangune (spelling), etc. The better SW portables tend to be real good on AM, and some countries have extra bands, or different frequencies for their bands so the more versatile the radio the more you can hear.

The AM/FM kit above is based on this IC http://kearman.com/images/YD9088.pdf

I suppose if you look at the data sheet, it does work by the same principal as a conventional superhetrodyne, i.e. Rf --> IF --> Detector --> Audio, but it's a super crappy radio on a chip integrated circuit with poor online reviews performance wise, minimal external components, and very little user adjustment/optimization

I picked the AM set because the conventional discrete superhet design looks a little more likely to perform well than the crappy all in one IC solution. Plus building it take longer and be a little more fun.


Agreed, I have a digital tuned sony ICF-XXXX (I don't remember the model off hand), which is just fantastic for said purpose, and even sounds great with stereo FM and my Grado SR-60 headphones. But sometimes when I travel I like to avoid taking anything I have any sort of attachment to, and for some reason I am always a little more curious about what's happening on medium wave, than FM.

Was that a Kelvin kit?
It had a cabinet that was identical to a early 50's Tele-Tone 4 tube radio.
It was a common 5 tube superhet with an isolated B-, as it didn't come with a back.
This weekend, I bought two transistor radio kits. One is a Kelvin AC operated, seven transistor. The chassis looks similar to the tube job, but it's stamped for transistor sockets and small IF transformers. According to the instructions, it's built in several stages and tested before going on. The transformer power supply, first.
The second one is an Elenco, PC board job. Battery operated. :thmbsp:

I really don't remember a brand, the case was a brown plastic.

Gregb

The Kelvin kit I have didn't have the transistors included. I looked at the bill of material and it didn't show the transistors. Seemed strange! The schematic shows all germanium types and it has a revision date of 1997. :sigh:
I personally don't get it! The instructions stated to check to see that all the parts were present, but didn't show the transistor types. :scratch2:

I have pieces of the Radio Shack 8 transistor radio 28-222 that I got as a gift back around 1977 with the white or tan/brown case.As I found it a couple years ago with the PC board broken and parts missing .What a shame.For some reason I never completed the kit when I got it.

For some reason these current kits look cheesy to me as I compare them to the old Radio Shack 28-222 kit.

As years went by around 1983 I picked up the cheaper Radio Shack 28-4029 radio kit model in the black case with 2 transistors and a LM386 for the audio amp .It sucks compared to the original kit.

As I was doing alittle homework on these kits the other day .I found a couple posts on ARF about the Graymark version of the old Radio Shack kit .The model number is or was Graymark AM radio model 536.

I would love to get my hands on one of these Graymarks.

http://www.antiqueradios.com/forums/...p?f=4&t=196521

http://www.esssales.com/graymark/ele...js-s4-500.html

The 1970's RS radio kit had these plastic style transistors like in the photo in the attachment and not the old metal germ 2sb54-2sb56 style transistors.

I'd love to have back my RS Archerkit AM radio I assembled in '74.. It got traded off that Summer. I was just an 11 year old kid and more interested in tube radios then.

That Graymark one might be tempting though..!

Yea .I'm close to your age Capt .I like to check out the Graymark kit out since its a clone of the 1970's RS radio.They must of bought the rights from the Shack to continue with it.

Maybe somebody can chime in with any more info on the Graymark kit and obtaining one.

In high school, 1983 I built the Graymark AM radio kit. In class we built it on the included breadboard and after I took it home, I built it on the pic board and installed it in the cabinet, all included. It was a well built radio and a good performer. The kit is still available today just as it was and I have thought of building one for nostalgia purposes.

I got the 6 transistor version today. It took me an hour to figure out some of the mystery connections. I have reached out to my Chinese friends for help with translation of the instructions.

My easiest guide to assembling is to find the 3v+ rail and mount parts from there. The xfmr was figured by ohming the pins as it can be mounted backwards. Electros are short wire as minus. LED is short wire as minus. Xstrs are marked. Small caps are marked. You just have to search the board for all the parts. Get your resistor guide nearby. I had a problem with the ferrite coil until I ohmed it and figured out the long side and the short side. A/B/C/D on the instructions. Battery mount can be any direction with the +/- and black/red as needed. There are still two yellow wires I have not figured out.

I stand to be corrected.

I got mine today too! The IF and oscillator coils were hard to tell apart until I realized the oscillator has no cap in the bottom. The audio transformer has a dot on it to indicate which way it installs but it sure isn't obvious. Aside from having the world's worst speaker I am happy with mine.

Yellow wires are for the speaker. The B+ dropping reaistor is marked on the board as 100k, but it really is 100 ohms and is also correct on the schematic. The board has several little solder bridges which have to be closed to allow it to work, presumably for measuring current to assist students to troubleshoot.

I bought both the IC radio and the transistor set. I have received and built the IC version and it works ok but not really very good. The AM works much better than the FM, gets all the local stations with good volume.

Gregb

Max,

Help me out.

I figured the coils.
My xfmr has no dots in sight. Where do I look.
What is the number of the B+ dropping resistor.
Where are the bridges to close?

Can you list a revised/corrected construction guide? I am close but the rest of us could use the help.

Dave A

R6 is marked 100K on the board and is really 100 ohms
The tip of my pen is pointing at the dot on the transformer, on mine it's a little raised bump so much as a dot. I ohmed out the windings on mine before I installed it and noticed the dot after. The board has a corresponding dot. The next message will show solder bridges A B C and D. Presumably students would use them to measure current of the various sections as per the X's on the schematic as a troubleshooting aid.

Here are the solder bridges

I picked up two KELVIN transistor radio (kits?0) this week. Both have the same transistor line-up. 2N412 osc, two 2N410 in the IF's, 2N408 AF Driver, and 2N3906 Push-Pull AF outputs.

Max, a few questions.

Do I have to solder the bridges for it to work?
Did you have to tune the coils?

Yes and yes. Do you have an RF signal generator ?

The speakers are so shallow, that there's no place for the cone to move.
The novelty radios have the same type speaker and the poor tone proves it.
BTW, can you post the schematic. It seems interesting. Schematics are the universal language. :thmbsp:

Sure, can take a shot of it later tonight. It's really nothing amazing though, in concept it is strikingly similar to the Westinghouse 99A I just got yesterday (although implementation is slightly different! :)

The fun for me was getting my 9 year old daughter to help.. she had fun with the colour codes and reading all the tiny numbers on the components.

That speaker may be swapped out.. I have a too far gone USSR built portable radio with a similar size speaker, and I think it will provide far better tone.

There is a video on youtube where someone makes a sticky-note into a speaker by placing foil coils 'wound' in opposite directions on opposite sides of the paper connected in series by punching a hole through the center. It sounded bad IIRC, but it did work.