[Hallicrafters] Re: [Boatanchors] Replacing recttubeswithdiodesquestion

[Rodger]

These threads have a way of quickly degenerating and these will be my 
last comments.

I add a dropping resistor because with increased plate and screen 
voltage most of the tubes are going to be operating at a higher 
temperature.  If there is a large safety factor in the original design 
then no problem with higher voltage.  Perhaps Henry Van Cleef is still 
reading these lists and he can repost his experiences with some vintage 
gear in which the original design was operating some of the tubes at the 
"ragged edge".   The suggestion by Bob WA2UEH to consider changing to a 
choke input filter can also be used in some cases, I did this with an 
SX-42 I bought years ago which had a replacement transformer with too 
much secondary voltage.  The choke input filter will result in 
substantially less output voltage which may be too low in some cases and 
hum reduction is going to be more difficult with this filter 
configuration but if these are not "deal breakers" in your application 
then it is worth trying.

The NTC inrush limiters I use have a fairly high cold resistance which 
drops quickly as they warm up due to current draw.  The ramp up in 
voltage can be easily measured.  Are they necessary for vintage gear?  
Perhaps not but a reduction in component stress is certainly not a bad 
thing.  I have within my personal collection over 150 pieces of restored 
gear ranging in size from an S-38 through a Desk KW and Gates BC-250GY 
and I have repaired and restored many pieces for others.  The use of 
inrush current limiters has removed that wonderful starting "bong" that 
the Halli SX-42 and 62 transformers often like to make but more 
importantly it has allowed the use of fuses sized to carry the running 
load of several of my transmitters instead of sized to carry the load 
due to current inrush.  A great practical article on the use of these 
limiters appears in the July 97 issue of Electric Radio.  It was written 
by Jim Garland (W8ZR) who was at that time still the university 
president at Miami of Ohio and he has great writing skills.  I recently 
purchased an older 1980's era Orr Radio Handbook and it has an 
interesting receiver construction article also by Jim.

I build the SS replacements as plug ins simply to make the gear easy to 
put back to "factory stock". 

These lists are always going to bring forth a variety of viewpoints and 
they are useful in that they allow us to examine a number of differing 
points of view.  I am simply sharing my experience and reasons; I have 
no psychological need to convert anyone to my way of thinking.  My 
advice on vintage gear is free so take it for what you think it is 
worth.  I only charge for business advice because that is the area of  
my doctorate and that is where I do my consulting work (which has paid 
for most of my vintage gear acquisition).

Rodger WQ9E

(Whose "real" job is Professor of Marketing)