Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Jun Sat 23, 2018 3:04 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 32 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Transistor radio kit
PostPosted: Jul Wed 02, 2014 12:16 am 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
I sprang for a little Chinese radio kit on ebay. Total cost $13.49 delivered and it arrived in 10 days.

I started assembling it today. Little tiny parts and one SMD chip. Went pretty well. The components ARE printed on the other side of the board.

Since there are no English instructions one is left to guess the mechanical aspects of things like the battery terminals, dial, etc. I'm pretty sure this as a kit made for students and its pretty easy to figure out. I hope to finish it tomorrow.

Attachment:
transistor.jpg
transistor.jpg [ 20.49 KiB | Viewed 5330 times ]

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 02, 2014 10:19 pm 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
Hey, it worked first time! Not much of a radio, though. My nearby AM swamps the BCB but I hear others underneath - like a crystal radio! I'll have to try again after hours when they drop to 1kw.

FM isn't as bad as I expected. Doesn't want to line up well with the dial but pulls in gobs of stations which is unusual for a portable set here. I think the FM section of the tuning cap may be a bit dodgy.

And the little poly speaker is hard on the ears to say the least - haha.

If anyone else decides to build one of these for entertainment I have photos now of the mechanical aspects that can be a bit confusing to figure out from scratch. Battery holders, dial assembly, etc.

All parts were correct as were all board markings. No leftover parts. Cheaper than going to a movie and buying popcorn :wink:

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Thu 03, 2014 4:35 pm 
Member

Joined: Sep Wed 22, 2010 1:36 am
Posts: 430
Location: sunnyvale Ca.
Do you have a link to it on ebay?
Thanks
Mel W.


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Thu 03, 2014 5:07 pm 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
I've seen them from other sellers but this is the one I bought from. He seems to be the cheapest.

http://www.ebay.com/itm/310930976499

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Thu 03, 2014 5:19 pm 
Member

Joined: Sep Wed 22, 2010 1:36 am
Posts: 430
Location: sunnyvale Ca.
Thanks Bill!
I have been looking for a cheep kit to build for fun.
Mel W.


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Thu 03, 2014 9:28 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 27582
Location: SoCal, 91387
Bill M wrote:
Hey, it worked first time! Not much of a radio, though. My nearby AM swamps the BCB but I hear others underneath - like a crystal radio!

Almost sounds like a TRF circuit. Can you post the print?

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Thu 03, 2014 9:47 pm 
Member

Joined: Sep Wed 22, 2010 1:36 am
Posts: 430
Location: sunnyvale Ca.
Here is the one in the eBay add.
Attachment:
radio.jpg
radio.jpg [ 98.21 KiB | Viewed 5195 times ]

Mel W.


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Thu 03, 2014 11:55 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 27582
Location: SoCal, 91387
Yup, no discrete IF stages.

IC 1 = FM
IC 2 = AM...The TA7642 IC is the same as the MK484*
IC 3 = Audio amp

* http://www.electronics123.com/s.nl/it.A/id.63/.f

I posted a thread a year or so ago, I think in home brew, about a receiver I made using one of these.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Fri 04, 2014 12:26 am 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
I tried it after WIVV drops power. Still no go. Way down away from 1370 it seems sensitive enough but I'd have to say that this radio cannot be used within a few miles of an AM transmiitter. I'll take it out fishing on Sunday and see how it does a few miles away.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Fri 04, 2014 7:57 pm 
Member
User avatar

Joined: Oct Wed 14, 2009 6:36 am
Posts: 5834
Location: New York USA
There is also an old-school AM radio kit with IF transformers, interstage and output transformers like the early 1960's. I haven't bought it, as the instructions are also in Chinese. It might be more useful as a source of parts to fix other collectible radios. They call it a "Summer Teaching Kit"
http://www.aliexpress.com/item/zx-921-R ... 18941.html

_________________
Diode Don, all problems rectified.

Someone with less knowledge than I had been in there before ....


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Sun 06, 2014 11:26 pm 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
That's not a bad deal, Don. I see its got free shipping as well. I'm tempted to check it out.

I took mine out to our fishing spot this morning. Its 8-10 miles from the local station. The radio performed fine out there.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Sun 06, 2014 11:48 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 27582
Location: SoCal, 91387
http://www.elenco.com/product/productde ... tor_and_ic)=NTk2

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 12:47 am 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
So I sprang for the one in the aliexpress link. I had my reservations since the whole aliexpress operation seemed to be that of an amateurish reseller operation. I didn't receive any paper work or schematic with the kit and it wasn't well packaged. I have whined to them so we'll see what happens.

In searching for X-291 schematic I ran across this site also regurgitated by aliexpress. Not hardly a confidence builder!
http://www.aliexpress.com/item/X921-typ ... 03359.html

If I ever do receive some documentation I'll post it on my website. But for the meantime I'd say stay away from aliexpress.

This is the China conundrum that we often consider but I've never had problems with Chinese sellers. Until now. Bad mark for all of them.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 1:45 am 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
I got a response from the native vendor to Ali...

ling yuan: I AM SORRY . IT HAVE NO SCHEMATIC .

Scratch aliexpress as a reliable source.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 3:53 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 27582
Location: SoCal, 91387
So you bought an 8 Transistor AM radio, in which you are the one stuffing the board instead of a factory worker.

What was your reason for buying it?

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 11:40 am 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
Hobby.

Interestingly, shortly after I whined a schematic appeared on the ad. Not enough to do anything with, though.

EDIT: Found a good readable 2000+ pixel schematic elsewhere on the interwebs. We'll see how it goes.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 10:17 pm 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
Managed to get it built and it plays pretty well. There's a number of different issues without documentation like having different numbers on the transistors provided and no specificity in the IF xfmrs. That took some research and guesswork. The split antenna coil configuration had me flummoxed for a while until I tried to put my guess into the case. Now I see why they split it. It will only fit one way. Oh, and the on/off switch on the volume control had sprung so that needed to be fixed.

It went together without a glitch. All the parts were there and correct. The only missing item was one precut speaker wire. Not a problem. No schematic vs board marking discrepancies. Wish I could say that about my Grundig 800!

Will wrestle a bit more with the alignment tomorrow.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 10:51 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 27582
Location: SoCal, 91387
How did you figure out the order in which the IF's went?

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 10:56 pm 
Member
User avatar

Joined: Jul Sun 21, 2013 12:21 am
Posts: 4969
Location: Vieques,PR 00765 USA
Well, one can was obviously the local oscillator. Red core just like they usually are. Then I went to Mouser's listing and they identify the 1st, 2nd, 3rd IF by color. First two matched. Only one left so it must be 3rd. Maybe a slightly different turns ratio. Plus they had numbers on them zx-920 thru -923. That lined up as well.
Must be correct. They all peaked up nice and sharp.

_________________
-Bill

Visit my homebrew page
www.sparkbench.com/homebrew/homebrew.html


Top
 Profile  
 
 Post subject: Re: Transistor radio kit
PostPosted: Jul Wed 23, 2014 11:25 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 27582
Location: SoCal, 91387
I figured either the color coding, or resistance measurements on each of the two IF can coils.

Can you post the colors for the 1st, 2nd, and 3rd IF's?

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
Post New Topic Post Reply  [ 32 posts ]  Moderator: Dave Doughty Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 9 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB