Restoring a 90 years old portable radio

I was recently given a Vatea Touring radio. One interesting thing about this set is that it was manufactured between 1929 and 1932. So it makes it at least 90 years old.  I was unable to determine the exact vintage of this set, the serial number stamped into the wood was unreadable.

Vatea was a Hungarian manufacturer of vacuum tubes, later absorbed into Philips. As far as it is known the Touring was the only radio set manufactured by them. Most likely it was actually contracted to some other company, but very little information survived about it. There are a number of Tourings in existence, but it is still a quite rare object.

 The other interesting thing is that this is a portable radio (hence the name Touring). It uses a 1.5V battery for filament heater and four 4.5V lantern battery for anode. There are connectors for external power supply, including the optional grid bias voltage for the amplifier tube. It uses 2 DX106 space charge tubes, which makes it possible to use a relatively low plate voltage.

One tube works as a regenerative receiver and the other as the amplifier, providing enough amplification to drive a pair of headphones. The built in aerial is a loop type built around the edge of the case and it also serves as the coil in the tuning circuit. The feedback coil is built the same way. There is a jack for external aerial too.

There is a coupling AF transformer between the detector and the amplifier and basically that is all. There is nothing exceptionally special in the schematics of the radio.

To properly make decisions about the restoration I had to examine the current state of the set. As there are little information available, I asked for photos of similar sets owned by fellow collectors.

 

These were the main issues:

• The wooden case was cracked and warped, the front panel was half detached from the frame.
• The radio was full of dirt and dust.
• Both variable capacitors were stuck.
  
• The connectors for the anode batteries were missing.
• The screw terminal for the filament negative was missing.
• All battery connections were implemented with dangling leads. The insulation was brittle and flaking on these wires.
• Most of the original internal wiring was replaced, the wire to the -optional- grid bias socket was missing.
• The tuning capacitor was not original.
• The coupling transformer was not original.
  
• The audion tube socket was relocated a bit, I have found the original screw holes.  
  

They seem a lot, but in fact for a radio of this age, it is quite ok. Even though it had been rebuilt at some point of time, most of the important parts were there. So the real decision for me was whether to restore it to the most original state possible or leave it as is and just fix the serious issues.

My decision was to rebuild. It has already underwent a lot of change, so it cannot be considered original. I do not see any problem in a repair that takes it closer to the original state. Since the case was cracked I needed to remove everything from the inside for the repair. That also gave an excellent opportunity to clean all the components.

Once the internals were removed I cleaned the case and glued it back together.

The stuck variable capacitors have been freed by using a little bit of penetrating oil on the shaft, then cleaning it. At that time I discovered that one of the dials had cracked due to the stress of the set screws that hold it to the capacitor's shaft. A bit of epoxy quickly solved this, with some glass fiber reinforcement at the back.

I opted for recreating the original wiring by using original looking thread insulated wires. All other componets have been reinstalled. Finally came the battery connectors. The anode battery connectors were missing, there were only holes in their place. I managed to find some copper thumbtacks that looked remarcably like the orginals. For the filament battery the screw terminal post was also missing, fortunately I found a replacement on eBay.

With everything in place, it was time to test. Using my newly fixed Agilent 6627A power supply I set the filament, anode and grid bias supply. The nice HP 8640B signal generator was supplying the RF, via the radio's external antenna connector. It was really cool to hear the old set woring, becasue it did work at first try!

The only thing left was to source four 4.5V lantern battery for anode voltage and a D cell for filament. The filament cell is coverd in a termporary cardboard envlosure on the pictire to the right. It is a future project to make a replica of the original battery. The 4.5V batteries are simply inserted in the slot with their tabs folded onto their side, thus connecting them in series for the 18V anode voltage. When working on battery power there is no grid bias, it is simply connected to ground with a shorting plug.

The large empty space next to them is a place for the headphones, unfortunaltey I do not have a headphone that fits there.

The radio works really well on batteries, I can receive loud and clear the two local stations on 540 and 873 kHz. There aren't that many stations than what used to be decades ago. But it is still nice to have a set in working condition that was manufactured about 90 years ago.