[Hallicrafters] Sky Challenger rectifier tube glowing cherry red

[wa4tuk-rf at comcast.net]

Years ago when the old First Class Radiotelephone license was worth having there was a question on the test along the lines of "What does it indicate when the plates of a high vacuum rectifier glow cherry red?"  The answer, of course, is the filter capacitor is shorted.

After all these years I finally get to use this!

There is the possibility of something else wrong but the filter cap is the first place to look. I would replace all of the electrolytics at this point because they are subject to drying out and failing by shorting or decreasing in value until filtering is impaired.

Others here will point out that the paper caps are also suspect and should be "shotgunned" due to leakage. Paper caps called "black beauties" and "little chiefs" have proven often leaky.

Wait for an evening when you don't have to rush and it can be a fun project.

Good luck!

Pat
wa4tuk
 -------------- Original message ----------------------
From: "Bob Young" <youngbob53 at msn.com>
> Hi All,
> 
> I picked up a Sky Challenger and powered it up slowly on a variac, the 
> output was very weak and the rectifier plates were glowing cherry red. I 
> tried a different rectifier tube brought it up again and this one started to 
> arc a bit at around 70 V. I assume I have a shorted filter cap and haven't 
> had the time to test it further. Any other ideas? What resistance would a 
> shorted or partially shorted filter cap read on a multimeter, incidentally 
> there was no hum.
> 
> I just bought an Eico 950B resistance capacitance comparator bridge,, it 
> needs a "comparator prototype or standard"?
> Anyone familiar with this thing, and what is the comparator it needs? a 
> known capacitance?
> 
> Bob Young
> Millbury, Ma 
> ______________________________________________________________
> Hallicrafters mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hallicrafters
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Hallicrafters at mailman.qth.net
> ----
> List Administrator: Duane Fischer, W8DBF **for assistance**
> dfischer at usol.com
> ----
> Hallicrafters Collectors International: http://www.w9wze.org