[NJARC] To recap or not to recap

[NICHOLAS SENKER]

I have never been a proponent of wholesale recapping of old receivers because I have repaired so many sets that worked fine after replacing the offending part(s) while leaving the old caps (including paper ones) in place.  That is, not until this weekend:  I was working on a 1940s Sparton table radio and after replacing some missing tubes, the set came on with a loud hum and garbled reception.  Recognizing this as bad filter caps, I replaced the electrolytics and some burnt resistors.  I also replaced some paper caps that were in the way of my work area.  Turning on the set it worked fine, the hum was gone and the reception was very good.  I played it about an hour and then reinstalled it into the cabinet.
The next time I turned it on it worked about a minute and then quit!  Removing the chassis again, I started checking voltages and found the screen voltage very low and the supply resistor running very hot (one that I just replaced).  The screen supply had five take offs and I systematically clipped each one until it was clear which one was causing the problem (the fifth one I clipped!).  Yes it turned out to be a shorted paper capacitor!
The moral of the story is that if I had replaced the caps in the first place, a relatively easy task and one which I ended up doing anyway, I would have avoided this problem.  In addition, I now had to reconnect all the leads I clipped, a tedious and messy job as the leads were short and difficult to get at.  This was twice as much work as recapping.
My advice:  recap!

Nick Senker