[Milsurplus] PP-109 Dead Vibrators

[WA5CAB at cs.com]

Somehow, I missed the original post.  In my experience, the most common 
failure mode for vibrators that haven't been used in decades (whether NOSB or 
Used) is that the tungsten contacts react with sulfer outgassed from the foam 
rubber sleeve and become non-conductive.  The details of the fix method 
I've always used varies depending upon whether the vibrator is a Series or 
Shunt type.  But basically you apply the 120 VAC line across each contact in 
series with a 15 to 40 watt 120 V incandescent lamp.  One lamp is put in series 
with the coil to pull the armature to one side and close half the contacts. 
 In the series type, this also puts it in series with the actual vibrator 
contact.  Additional lamps are put in series with the remaining contact(s).  
The armature is common to all circuits.

Lamp sizes that I use are as follows:

For the lamp in series with the coil
< 6V   40W
6V 40W or 25W
12V   25W
24V   12/15W

All other contacts, 12/15W.

For shunt type, one lamp is put in series with the coil only (see * below). 
 Tie the two contacts, one of which is used as the shunt contact, together 
and put a second lamp in series with them.  Run the setup until the second 
lamp lights.  disconnect the two contacts and determine which is working.  
Connect it as the shunt contact and put the second lamp on the other contact.  
If you have enough lamps, connect additional ones to the other contacts.  
Run the setup until all lamps light or flash.  May take several hours.  
Dropping a diode (1N4008) in series with the coil may speed things up.

*  If the shunt contact is internally connected to the coil you can't use a 
separate lamp on it and if repair is successful it may take many hours.  

Also, the procedure will not work with a VB-5 because it has a 470 ohm 
resistor across the vibrator contact internally.  And to add insult to injury, 
the aluminum cans on every VB-5 I have ever fixed are the only ones i've 
encountered that consistantly crack when you try to open them up.  You'll have 
to have a non-VB-5 organ donor to supply a replacement can.

In a message dated > --------------------------------------------------
> From: "David Stinson" <arc5 at ix.netcom.com>
> Sent: Tuesday, December 03, 2013 7:24 AM
> To: <milsurplus at mailman.qth.net>
> Subject: [Milsurplus] PP-109 Dead Vibrators
> 
> >I know this has been covered before, but I can't find it.
> >
> >Anyone have a good, non-destructive procedure for 
> >reviving dead 6-volt, 7-pin vibrators from the PP-109
> >power supply?  This one is recapped and waiting to 
> >power some bench projects if I can "wake it up."
> >73 Dave S.

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480