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 Post subject: Need help aligning this...
PostPosted: Oct Mon 01, 2007 12:22 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Earth
Any thoughts/hints welcome! This thing is verrrrry tiny.

It's a Zenith "my radio". The only model number I can reference is RD-14. It's a tiny "owl" made to be worn as a necklace, or in a shirt pocket.

I don't know if there even is a Sams on this??!

How do I go about aligning it? Reception is weak, my "local" radio station in my house (courtesy of SSTRAN) comes in loud and clear, but the others around the dial are faint. There are NO electrolytics in this radio.

There are (2) trimmer cap screws on the back of the plastic tuning capacitor box assembly. I tried playing with them but can't tell which is for the antenna trimmer and the osc. adjust. It does have tiny IF cans as you can see.

Image

I would appreciate any help.


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PostPosted: Oct Mon 01, 2007 3:33 am 
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Location: Brunswick, ME 04011 (USA)
...let's see...to determine which trimmer is the OSC, tune in a station, preferably around 1400 kHz. You will notice that two of the four tiny nuts in opposing corners of the tuning capacitor have trimmer capacitor plates attached to them. If you take a small piece of bare wire and touch those two nuts with it, you will note that touching one of them will cause the station to detune; that will be the OSC trimmer...
...you need to align the IF first. Apparently there is one fewer IF transformer than usual (the white and gray cores are the IFs; there was typically also a yellow one in most transistor AM radios, which I don't see in this radio...the red one is the OSC coil), so you might not get the usual sensitivity out of this radio. You inject a 455 kHz signal (at the lowest useable level) and peak the white and gray transformers...then you set the dial to 600 kHz, inject (or loose-couple) a 600 kHz signal and tune the red coil to bring the signal on frequency; usually you then move the winding on the ferrite bar antenna to get a peak...then tune the dial to 1400 kHz and inject a 1400 kHz signal, adjust the OSC trimmer that you identified above to bring the signal on frequency, then use the ANT trimmer to get a peak. Now, these two OSC adjustments interact with each other somewhat, so you will probably have to go back and forth and repeat them a couple of times...
...I'm sure you already know most of this anyway... :mrgreen:


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PostPosted: Oct Mon 01, 2007 4:09 am 
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Joined: Aug Mon 28, 2006 3:07 am
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Location: Boston area
I'm sorry, I can't help you with this but I think the whole idea of this radio facinnating.
It kind of reminds me of a tiny AM radio I won at an amusement park as a kid back in the early 70's.
Of course because of its poor performance and cheap construction, I soon trashed it.
But today I wish I still had it.


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 Post subject:
PostPosted: Oct Tue 02, 2007 5:41 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Eagleville, PA
Dr. Radio:

Here's a tip that maybe you and others can use.

You can use the SSTRAN to generate the IF frequency for aligning the IF. It will tune to 450 Khz or 460 khz (sorry not 455 khz exactly), but you can bet it will be right on frequency.

The frequency switch settings are as follows:

450 khz:
1 2 3 4 5 6 7 8
ON ­ ON ­ OFF OFF ON ­ OFF ON ­ ON ­

460 khz:
1 2 3 4 5 6 7 8
OFF ON ­ OFF OFF ON ­ OFF ON ­ ON


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