[R-390] More Ideas for the Y2.005K FAQ, etc

[ToddRoberts2001 at aol.com]

In a message dated 12/25/2005 3:34:38 AM Eastern Standard Time, 
r390a at bellsouth.net writes:
Some time ago someone -- was it Nolan? Someone put together a parts  
breakdown on Amperite Ballasts that showed the differences between a  
3TF7, 3TF4, etc so folks could "decode" any mystery ballasts they  
might find out in the wild.  Is that information still floating  
around somewhere?
More info as it pops through the cobwebs. :-)
Tom NU4G

Tom - About all the information you could ever ask for about the Amperite 
Ballast tubes used in the R-390A are located in the R-390A Pearls Of Wisdom 
pages. Here is a recap of the info - 
Amperite numbering system in general (not consistent!)
First Digit - regulated maintain current in tenths of an ampere
First Letter - envelope type
Second Letter - not sure, version perhaps?
Last digit - threshold voltage in volts? 
Thus 3TF7 = 0.3 ampere regulated maintain current range, T6-1/2 bulb 9 pin 
miniature, 7 volts threshold voltage
         According to Amperite specs the actual regulated voltage drop range 
is from 8.6-16.6 volts, so the 3TF7 will try to maintain a regulated current 
of 0.3 amps (300 milliamps) within a voltage drop range of 8.6-16.6 volts. The 
voltage drop across 2 6BA6's in series drawing 0.3 amps will be 12.6 volts and 
with a 25.2 volt filament circuit the required voltage drop across the 3TF7 
will be also 12.6 volts, therefore the 3TF7 will be operating right in the 
middle of its voltage drop range for optimal regulation.

We all may want to keep in mind the R-390A Pearls Of Wisdom pages so we don't 
needlessly repeat info that is already out there? 73 and Merry Christmas to 
All - Todd WD4NGG