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


It is currently Oct Wed 16, 2019 3:13 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 4 posts ] 
Author Message
 Post subject: Magnavox 70s console solid state unit chassis R321-12CA
PostPosted: Jan Wed 23, 2019 8:21 pm 
New Member

Joined: Jan Wed 23, 2019 8:08 pm
Posts: 3
Hi all, new guy here so hope I'm posting this in the right forum. Well trying to wrap up this radio from hell. The last problem I am having is in the FM section. I can't get anything but my local station, which is coming in on several positions on the dial. Seems like the oscillator isn't running as tuning has no effect. I've tried listening for it with a portable but nothing. The portable picks up the oscillator from other FM receivers I have. As you can see, the oscillator circuit isn't very complicated. Not many components at all. Original measurements showed voltages way off on Q1, the FM osc. The original transistor had collector to emitter leakage. I've replaced it and now the voltages are more in line but still no difference. I have replaced R1, 2, 4. I have replaced or subbed C7, 9, 10, 11 and 17 even though they test good. I have tested C15 and the tuning gang. I have disconnected VC1 the afc diode then reconnected later. L3 is the only inductor in the circuit which is only a few turns of coiled wire. The spacing of the turns is loose so that I can see there's nothing shorted and it does ohm out. Q1 cross references to an ECG 161 as per parts list notes which I installed. I am totally stumped on this one. I keep coming back to the osc transistor and have subbed 3 other NPN silicon FM RF or oscillator capable transistors in addition to the ECG 161, but still no difference. Even subbed a UHF type! Perplexed isn't the word. Sorry for the long dissertation.

Ron


Top
 Profile  
 
 Post subject: Re: Magnavox 70s console solid state unit chassis R321-12CA
PostPosted: Jan Thu 24, 2019 2:25 am 
New Member

Joined: Jan Wed 23, 2019 8:08 pm
Posts: 3
Attachment:
IMG_2102.JPG
IMG_2102.JPG [ 38.74 KiB | Viewed 299 times ]
Here is the Sams schematic for the Magnavox!

Ron


Top
 Profile  
 
 Post subject: Re: Magnavox 70s console solid state unit chassis R321-12CA
PostPosted: Jan Thu 24, 2019 3:56 am 
Member
User avatar

Joined: Mar Tue 30, 2010 2:24 am
Posts: 8402
Location: Lehighton, PA.
Welcome to ARF from a fellow Philco Phorum member. :)

Larry

_________________
kb3wbb


Top
 Profile  
 
 Post subject: Re: Magnavox 70s console solid state unit chassis R321-12CA
PostPosted: Jan Thu 24, 2019 6:09 am 
New Member

Joined: Jan Wed 23, 2019 8:08 pm
Posts: 3
Thanks Larry, just expanding my horizons you might say! :D


Top
 Profile  
 
Post New Topic Post Reply  [ 4 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: richfair and 5 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB