[MRCA] SCR-284 Part 4 Posted

[J Mcvey]

 There isn't much practical modern info about those PE-104 supplies, so your article will be helpful to those who wade into a restoration of this supply.
I usually find that the bridge rectifier is bad too . I've experimented with different rectifiers because the forward drop is very  critical when we're talking about 1.5V  output! Silicon bridges have too high of a forward voltage. (0.6 X2). There are miniature schottkey smd bridges that work OK , but if you want to roll your own , junk box antique 1n91 germanium diodes do pretty well too. ( leaky but a whole lot better than the selenium that is in there)

I never got too crazy with the ballast, but you make a valid point about tube life.I have been using two 1N4001 diodes in series as a "stop gap" at about 1.8 volts. I didn't want the circuit to draw current unless absolutely necessary to protect the filaments.  The "ballast"  design is similar to the crowbar concept where full current flows through the device upon a fault, so whatever diode you use needs to be able to handle the current and dissipation if conduction does occur.The crowbar, on the other hand, is often intended to short out and blow a fuse to protect the circuitry. The ballast needs to survive.

These supplies tend to  generate the correct voltage if the  stated supply voltage is applied. ( 12.6 or 6.3) . However the problem occurs when the radio is running while the vehicle is charging , which brings the supply up to 14.5 volts.
Jim. AC2EU


    On Sunday, June 30, 2019, 2:53:23 PM EDT, B. Smith <smithab11 at comcast.net> wrote:  
 
   I've posted part 4 of my SCR-284 series with information on the PE-104 vibrator supply.
        Part 4 covers:
 ID of your version of the PE-104
 Filament Ballast Info
 Vibrator Info
 Test Tools
 Testing using low voltage AC.
 Capacitor replacement.
 http://k4che.com/SCR-284/SCR-284%20Part%204/SCR-284%20Part4.htm
 Z
 
 
 
 ______________________________________________________________
MRCA mailing list
Home: http://mailman.qth.net/mailman/listinfo/mrca
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:MRCA at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/mrca/attachments/20190630/5d4d8436/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: jnopijfnojpgjcak.gif
Type: image/gif
Size: 9511 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/mrca/attachments/20190630/5d4d8436/attachment.gif>