1958 Ever Ready “Sky Countess” Vacuum Tube Radio Repair & Restoration

A couple of months ago, I bought a vintage 1958 Ever Ready “Sky Countess” vacuum tube AM radio set in an antique shop in Norton, Bailey’s Vintage Supplies.

The “Sky Countess” is a portable battery-powered four-tube superheterodyne radio receiver, with a channel switch (AM medium-wave and AM long-wave) and internal AM antenna.

Battery-powered tube radios are interesting and quite unusual because vacuum tubes require high voltages to operate, unlike more modern solid-state electronics – as such, the Sky Countess used an AD35 1.5V battery for the low-tension supply (valve heaters) and a B126 90V battery for the high-tension supply (valve plates).

If you’re interested in how “superhet” radios work, “Transistor Superhet Receivers” by none-other than Sir Clive Sinclair himself is an excellent book.

Sky Countess was in reasonable physical shape, however it was in unknown operating condition – not a major surprise given the specialist batteries.

Radio Disassembly & Inspection

I wanted to take a quick look inside the set before trying to power it up, to see if I could spot any obvious problems beforehand.

The Sky Countess is an easy radio to disassemble, and only two captive flathead screws hold the front cover on – the front cover then comes out, with the circuit board attached.

The radio chassis seemed to be in original condition – the battery cabling was intact, and even the elastic bands fitted around the tubes from the factory (to help keep them in place during transport) were still in place, albeit quite crispy.

Power Supply Build

To be able to test and use this radio, I needed to find a suitable replacement for the 90V (HT) and 1.5V (LT) batteries. The LT battery isn’t a problem, you could use a 1.5V AA battery if you wanted to, but unsurprisingly you can’t really buy 90V batteries. It’s possible to build a suitable battery (i.e. by putting ten PP3 9V batteries in series), but you’d need a suitable connector if you didn’t want to modify the radio, and you’d still have the issues associated with battery supplies (limited charge, potential for leakage, etc).

I decided to use a mains adapter instead, which takes a standard 230Vac mains input and provides a 90Vdc output and a 1.4Vdc output to emulate the two original batteries, and fits into the footprint of the original 90V battery.

I even bought an original (and completely dead) B126 battery on eBay, with the intention of gutting it and using it to house the mains adapter.

I built the mains adapter up such that the 90V connector on the chassis plugged into the original connector from the gutted B126 battery, the 1.5V connector on the chassis plugged into a pair of female bullet crimps (both different sizes based on the battery polarity), and the mains input plugged into a female figure-eight mains connector (instead of modifying the case to fit a permanent flying lead).

I tested the power supply to make sure that the output voltages and their polarities were correct, then tried powering up the radio – unfortunately, it seemed to be completely dead, with the occasional “pop” from the speaker.

Radio Repair

Electronics of this vintage usually contain components that frequently deteriorate or fail with age, and can (at best) cause damage to the tubes and other circuitry if left unchecked – radios from this era therefore need to be inspected and serviced as required.

I took this opportunity to clean up the chassis, in order to get a good look at everything that needed to be worked on. I removed the chassis from the front case to work on it, which required unscrewing the chassis, unscrewing the power switch, and desoldering the speaker.

I cleaned the chassis, components, and tubes using a general degreaser and a microfibre cloth, carefully removing the tubes to do so (which meant removing the elastic bands). I also cleaned all of the tube sockets and the volume control with contact cleaner.

The Sky Countess has a very useful service manual, which includes a parts list and a chassis layout, which can be very helpful during servicing, particularly for identifying potentially problematic components.

I took notes of all of the parts that would need to be replaced, including an electrolytic capacitor and several paper/wax capacitors.

Electrolytic Capacitor Replacement

Aluminium electrolytic capacitors are commonly used for filtering, smoothing, and decoupling in both high- and low-voltage electronics. They typically comprise aluminium windings which are coated with a liquid electrolyte, which can dry out over time (negatively affecting the performance of the capacitor, often causing them to fail dead-short), or leak out and cause corrosion to the PCB and surrounding components.

The Sky Countess is a 1950s radio set, and as such was made with 1950s electrolytic capacitors – these are far inferior to modern equivalents, and coupled with their advanced age, they should ideally be replaced for longevity purposes.

Electrolytic capacitors are polarised, meaning that they must be installed in the correct orientation, otherwise bad things usually happen. It is therefore important to take particular care to ensure that the value, voltage rating, and orientation of the new capacitor are correct – this is more difficult with point-to-point wiring and early circuit boards as the correct connection points aren’t necessarily obvious and the polarities aren’t marked, so it’s important to take plenty of “before” pictures to refer back to later on.

There is only one electrolytic capacitors in this radio:

• 1 x 8uF 150V axial electrolytic (replaced with a 10uF 160V 105C part).

The new parts are significantly physically smaller than the originals, which just goes to show how far capacitor technology has advanced over the past 70 years.

It’s also difficult to get exact matching replacements for some of the values – for example, I substituted a standard 10uF capacitor for the non-standard 8uF capacitor. This kind of substitution should be okay for electrolytic capacitors, as they typically have a wide manufacturing tolerance anyway (up to 20%) – if in doubt, check the parts list in the service manual for specified tolerances. It is important to use a capacitor with the same or higher voltage rating as the original, and if you’re going to all this effort to replace these parts, you should make sure to use high-quality modern replacements.

It was definitely worth replacing this, as the original part tested as very leaky (electrically) using my ESR meter – it had basically started to turn into a resistor over time, and would no longer properly block DC.

Paper/Wax Capacitor Replacement

The Sky Countess also uses paper/wax capacitors – these antique capacitors are literally made from rolled-up paper and covered in wax, and like the electrolytic capacitors are also prone to failure from advanced age, including electrical leakage or open/short circuits.

These are far inferior to modern equivalents – most notably polypropylene, polyester film, and metallised film capacitors (ceramic capacitors are micro-phonic, so are generally not suitable for use in these circuits) – and like electrolytic capacitors these should ideally be replaced for longevity purposes.

To get proper access to all of these parts, I needed to remove the tuning capacitor.

There are eight paper/wax capacitors to replace in the Sky Countess:

• 3 x 0.01uF 350V (axial TOC) – swapped for 10nF 630V polypropylene axial.
• 5 x 0.04uF 150V (axial TOC) – swapped for 47nF 400V polypropylene axial.

I removed and replaced the parts one-by-one using my desoldering station, making sure to keep their leads as short as possible, using the parts listed above.

Radio Reassembly & Testing

Reassembling the radio is just the opposite of its disassembly. The chassis and power switch are fitted back onto the front case, the front controls refitted, and the speaker reconnected; I also refitted the tuning capacitor and vacuum tubes.

I tried powering the radio on, and it now gave audio from the speaker. I tried tuning it in, and it seemed to work perfectly now!

I took this opportunity to give the case interior and exterior a thorough clean using degreaser and a microfibre cloth, to get rid of the worst of the dirt and paint – I had already cleaned up the dials and dial surround when they had been removed previously.

Everything turned out quite nicely!

Overall, I’m extremely happy with the outcome of this restoration.