New Life to All American Five Part II - Filter Capacitor Replacement.

Easily the most common failure point with vintage radios are the electrolytic capacitors, primarily those in the power supply.  In anything over 40-50 years old, it's virtually guaranteed that the filter capacitors have either failed or are soon going to.  While I generally abhor the "shotgun" method of replacing anything that could possibly be bad, I do replace filter caps before powering up any piece of ancient electronics. 

This set uses a fairly typical arrangement for All-American Five tube sets: A single cylinder containing three electrolytics - Two 40 uF 160 Volt capacitors to filter the power supply and one 20 uF/25 volt capacitor used to bypass the cathode of the audio power amplifier tube.  I've heard that there are vendors who can supply original-style replacements, but the original can be "restuffed" with new replacement parts for about the cost of shipping of the original-style replacement.  So, being cheap, that's what I'll do with this set.

This is the "before" shot of the capacitor mounted on the top of the chassis.  Note the phenolic insulator at the base - this must be re-used and care taken that the capacitor housing doesn't short to the chassis as it actually "rests" a couple volts below ground potential.

The view from below.  This is where I scribble notes detailing what goes where before I warm up the iron - I'm not going to remember how it's wired, and tracing from a .pdf scan of a photocopied schematic is a drag.

The cardboard cover of the capacitor is typically held to the aluminum cylinder by a blob of tar.  This was the hot-glue of the day!  

 

 

 

To get at the guts, I carefully undo the crimp where the cylinder is attached to the base.

 

 

 

The dried-out capacitor elements can usually be removed by pulling it out by the terminals using a pair of pliers.  Some fight harder than others, and you have to be careful not to damage the terminals as we're going to reuse them.  In this cap, the guts were held to the cylinder with another tar blob - pretty typical.

The new caps are installed to the original terminals.  In order to wire them, drill small holes in the base plate and route the leads to the underside.  The original wires extending from the terminals are aluminum and won't take solder.  With a bit of care, the holes/wires can be all but invisible. 

I secure the caps and wiring with a little tape, just in case someone ever decides to operate the radio in a paint shaker.

The guts are stuffed back into the cylinder and the cylinder is re-crimped to the base.

Bottom view.  The crimp isn't pretty, but it's not going to show.

All the wires get reconnected according to the notes taken earlier.  Notice the yellow capacitor with the green leads - This was connected to one of the terminals on the electrolytic, and since I intend to replace all of the old paper caps anyway, I replaced it while it was halfway disconnected.

And the "After" shot.  Looks the same as the before - which is exactly what I want!

This is where I stop, visually inspect everything and - using an isolation transformer - apply power to the set and check performance before proceeding to replacement of the paper caps. Most of the time, the set will come to life somewhat - there are bound to be other problems.  These should be noted before continuing.  This set was pretty typical, it played well at first, but slowly crapped out over time.  Troubleshooting revealed a bad rectifier tube - no big deal, got one coming!  Meanwhile, I cobbled together a solid-state replacement so that I'll be able to continue refurbishing it while waiting on the tube.

This looks like a good stopping point - More to come!