[EICO] (no subject)

[pbmanis at bellsouth.net]

Hi Tim,

Thanks for your comments! 
> > I noticed that you used 100 uF/450 V instead of the original 40 uF/450V.
> 
> In a not-identical restoration (my 720 transmitter), I had great
> success with making the note sound sweeter by beefing up the filter
> caps similarly. I was not able to find axial lytics in that voltage
> range but the radials and some extension wire seemed to do the job
> nicely enough.
>
That should be justification enough for me!

> One worry was that the rectifier tube wouldn't handle the higher
> peak current but I have not yet melted it :-).

Yes, I considered this, but seems the tubes are less sensitive to inrush currents than solid state 
bridge rectifiers. I can tell you about a Swiss-designed solid state power supply that used 0.1F and 
the 50A bridges that we had to replace all the time! Dropped the filter cap to 0.033F, everything 
worked great, and the bridge has yet to go....The device was rather special purpose, but they wanted 
a very constant current across a platinum ribbon filament.

> 
> > Did you also replace the filter 
> > choke (listed as a 5/25H choke - e.g., swinging)?
> 
> Do these "go bad", or were you talking about changing the filter choke
> so it's a better match to the new caps?

I was thinking about the match with the different cap size, but I haven't gone back to the reference 
material to figure out the difference.

> 
> Looking at the dropping resistors inside my 720 I always think
> "there had to be a better way to do this". But maybe there wasn't!
> A second B+ winding would've required additional rectifier tube
> and additional filtering, in what was undoubtedly an already
> cost-sensitive market. I mean the $70 or $80 list price in
> early 60's dollars would be $300 or $400 today after adjusting
> for inflation...
> 
> Tim.
> 

Thanks,

--Paul NC3G