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


It is currently Apr Sun 05, 2020 4:48 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 8 posts ] 
Author Message
 Post subject: 1967 Sapphire V car radio problem
PostPosted: Feb Tue 11, 2020 7:35 pm 
New Member

Joined: Sep Sat 26, 2015 10:44 pm
Posts: 9
I have a 12V 1967 Sapphire V car radio problem. It tunes in stations, but it oscillates between stations. When tuned near a station the oscillation frequency decreases and zero beats on the station. This happens above and below the station. When on the station it sounds a little distorted. I have not attempted the alignment procedure.

I have a second 1967 Sapphire V car radio that does not oscillates between stations and works great.

Any help would be greatly appreciated.

Here is a great source of free Photofact manuals for VW radios and other car radios.

Link to all Photofact manuals for VW radios:
https://www.thesamba.com/vw/archives/manuals/radios.php

Link to 1967 Sapphire V Photofact manual:
https://www.thesamba.com/vw/archives/ma ... 7_late.php

Both radios are manufactured by Motorola, the Photofact manual listed above if for the Bendix radio.
Here is a link to a 1966 6V Sapphire III radio manufactured by Motorola, it should be almost the same as the 12V 1967 radio. I don't have a link to the Motorola 12V 1967 Sapphire V radio.
https://www.thesamba.com/vw/archives/ma ... re_iii.php

Thanks,
Wayne


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Tue 11, 2020 8:19 pm 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 12012
Location: Mountains of Mourne. Ireland.
Replace all the electrolytic capacitors and... out of tolerance resistors.
Quickly measure resistors in circuit, if you see something funny, lift one leg and re-measure.

Also check out...
C12
C15
C16
C17
C22
C26
and C27
they may have originally been paper capacitors?

Perform an alignment.

------------

These linked videos will show all alignment and dial-tracking procedures.
viewtopic.php?p=3128591#p3128591

------------

Searchable... Aerovox, Mallory and Sprague capacitor catalogs from the 1960s can be found via this link...
viewtopic.php?p=2736389#p2736389

Greg.


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Tue 11, 2020 8:29 pm 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 12012
Location: Mountains of Mourne. Ireland.
Don't go looking for Electrolytic capacitors that are rated at 4V and 16V

The Voltage rating of a capacitor is how much Juice that it can handle - this can be increased.

Modern day electrolytic capacitors have become so much smaller since the 1960s
viewtopic.php?p=3029559#p3029559

Greg.


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Wed 12, 2020 9:07 am 
Member
User avatar

Joined: Mar Mon 17, 2008 5:05 am
Posts: 5888
Location: Ashhurst, New Zealand
IMHO I would suspect the electrolytic on the AGC line.

_________________
Cheers - Martin ZL2MC


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Wed 12, 2020 10:51 am 
Member

Joined: Jan Thu 16, 2020 12:29 am
Posts: 292
majoco wrote:
IMHO I would suspect the electrolytic on the AGC line.


I was thinking that myself, because it sounds like oscillation in the IF stages, but then I looked at the schematic and thought..hmmm.

In a lot of pocket transistor radios, there is just an electrolytic only on the AGC line, if it goes low uF and high ESR, the IF oscillates.

But in this particular type of radio, there is bypassing after the AG electrolytic with other capacitors and R-C filters. So, in this radio, if the AGC electrolytic lost its capacity, likely it would just shorten the AGC time constant and not result in IF oscillations.

I would wonder in a design like this, if one of the IF stage transistors might be unwell. You will notice that there is no neutralization around each IF stage. This is only possible if the transistor there has a very low collector to base feedback capacitance.


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Thu 13, 2020 7:50 pm 
New Member

Joined: Sep Sat 26, 2015 10:44 pm
Posts: 9
Thanks everyone, the AGC electrolytic lost its capacity.
After replacing C12 the radio works great.


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Thu 13, 2020 9:05 pm 
Member
User avatar

Joined: Mar Mon 17, 2008 5:05 am
Posts: 5888
Location: Ashhurst, New Zealand
I didn't look at the schematic - just guess work!

_________________
Cheers - Martin ZL2MC


Top
 Profile  
 
 Post subject: Re: 1967 Sapphire V car radio problem
PostPosted: Feb Fri 14, 2020 12:27 pm 
Member

Joined: Jan Thu 16, 2020 12:29 am
Posts: 292
majoco wrote:
I didn't look at the schematic - just guess work!


Good guess !


Top
 Profile  
 
Post New Topic Post Reply  [ 8 posts ]  Moderator: Dave Doughty

All times are UTC [ DST ]


Who is online

Users browsing this forum: Ed in SoDak and 4 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB