INTRODUCTION
The RECEPTION SET A.E.W.1 (N.Z.) is an amenities receiver, designed for the entertainment of the troops, when they are off duty. It is a standard superheterodyne receiver, with one IF stage (455 Kcs), one RF stage, and a vibrator power supply. It will operate from 6 volts DC current at about 2 amps. It was made in New Zealand. It is intended for front line operations, as it has no mains AC input, and is in a sturdy steel box. It covers shortwave as well as the broadcast band. There are 4 bands: 550-1600 Kcs (broadcast band), 6-12 Mcs, 12-17 Mcs, 16-24 Mcs. It is different from some amenities receivers, in that it does not have a phono input, or a microphone input.

Front

MECHANICAL DESIGN
The case is a heavy gauge steel box, with an enclosing lid. The DC supply cable fits inside a pocket in the lid. Also in the lid is a diagram showing how to connect the speaker and aerial. There is available externally, an aerial wire, ground wire and spike, and a speaker. Two speakers can be connected if required. The radio itself is on a plated steel chassis, with the vibrator power supply, in an enclosed steel box, and rubber mounted.

The front panel is painted in green wrinkle paint, and there are metal plates fitted to explain the control knobs operation. In the centre is a large rectangular clear dial, with a slight bulge. To the left of this are 2 terminals, AERIAL and GROUND, with the VOLUME control beneath them. To the right of the dial are 3 terminals for the speaker, showing connections for one or two speakers. The TONE control is beneath them.

Below the dial is the band change switch, an on/off switch labeled BATTERY, and the TUNING knob. There is a Plessey name on the dial, but hidden from view.

ELECTRICAL DESIGN
All the valves are 6 volt AC heater types. The audio output valve is a 6V6GT using cathode bias, which drives a speaker transformer. The speaker transformer output has a tapped secondary, to allow connection of one or two speakers, of 500 ohms impedance. There is a TONE control connected to the anode circuit. The Service Bulletin mentions that this control may be fitted to the PA grid circuit on some radios. The audio comes from a 6Q7GT triode amplifier. It has a diode rectifier to demodulate the audio. The other diode rectifies the RF signal and generates an AVC voltage, for the IF and RF amplifiers. There is no AVC delay, as the cathode is connected to ground. The IF amplifier valve is a 6U7G, and has a double tuned IF transformer on the input and output. The screens of the IF, RF, and MIXER are connected together. The MIXER valve is a 6K8GT, with the triode connected as the local oscillator. The hexode section is the mixer. The RF amplifier uses a 6U7G valve. There is a 3 gang tuning capacitor, to tune the RF amplifier input and output coils, and the local oscillator coil. The coils are switched by the band change switch. Note that there is only a trimmer for the RF amplifier coils, for the high frequency end, there is no slug for the lower frequency end of the bands. The two lower frequency oscillator coils do have an extra padder trimmer. The vibrator supply has a 6 volt DC input and uses a synchronous vibrator. The Service Bulletin mentions that the vibrator is a 12 volt type, with "especially adjusted" contacts.

Inside

RESTORATION
The radio is in good condition, and very clean inside. The only noticeable problems are some rust on the chassis, where it has been sitting in a small amount of water. There is also some rust on the front panel screws. The rust cleaned off easily. The case was sanded and repainted in the rusty areas. The carry strap was missing, rotted away, so a new one was fitted. The volume control was very stiff, but this freed up with the application of some WD40 solvent. The dial was in good condition, except that there was a small mark, where the dial pointer had been resting. The dial string was in good condition, and the radio mechanically tuned from one end of the dial to the other. The valves were all GT sized except for two, the RF and IF amplifiers.

The dial was dismantled and the metal scale cleaned. The Red mark from the dial pointer came off by using soap. The screws were cleaned and it was re-assembled, although restringing the dial cord was a little tricky. The scale was marked Plessey.

Dial Scale

The vibrator supply was removed and placed to one side. A voltage of 6 volts DC was applied from a bench power supply, and the current peaked at 2 amps, then it slowly reduced to 1.6 amps. This appeared to be normal. A speaker was wired to the audio output terminals. Another bench power supply was connected and 150 volts DC was applied to the vibrator output terminal strip. Surprisingly, some noise was heard in the speaker, so an aerial was attached. Several stations were tuned in on the broadcast band. The grid of the audio output valve was checked, and there was plus 4 volts DC present, so this indicated a leaking coupling capacitor. The circuit was referred to, and it was decided to replace all the paper capacitors, with new ones. The original capacitors were made in the USA and appeared to be in good physical condition. The electrolytic cathode capacitor on the audio stage was replaced. Also replaced, but left in place, were the main HT capacitors which were can mounted. All the resistors were checked, but none were replaced, despite two being high in value. Some resistors were the BODY/TIP/DOT style and others were more modern striped tubular style.

Vibrator

The vibrator supply was dismantled, and the 3 paper capacitors were replaced. The vibrator did not run. It was taken out of the can, and the points cleaned. When working correctly, the supply was reassembled, and wired back into the radio. The rubber mounting grommets were replaced, as they were hard and brittle.

Underneath

The radio was aligned at the IF frequency which was a little low. It was 100 micro-volts for a 10db signal to noise ratio, at 455 Kcs.

The broadcast band and the first short wave band aligned easily, with the Philips beehive trimmers. The two higher scales were hard to align, as the aerial trimmers had little effect. The top scale would not peak at all. A Grid Dip Oscillator (GDO) was used to check the coil resonances and the dial alignment. The top band was way too high, and the next band was fine, but would not tune the lower end on the band. Two paper capacitors were found underneath the coil assembly. They were replaced, with difficulty. However, there was no change in the alignment. Careful study of the circuit, showed that all the bands were tuned with a 500 pF variable capacitor (C1A). When the first short wave band is selected, a series capacitor is added (C3A), to reduce the tuning capacitance. The top two bands, have another capacitor switched in (C2A), to further reduce the tuning capacitance. This was 100 pF on the circuit diagram, but when measured on an LCR bridge, was actually only 2 pF. This was replaced. The GDO confirmed that the coils all tuned correctly. The top two bands now tuned properly, and the sensitivity also improved markedly. The sensitivity for the four bands varies from 3 to 10 uV, for a 10 dB Signal to Noise ratio.

Band 1:	550 - 1600 Kcs	8 -10 uV
Band 2:	6 - 12 Mcs	7 - 3 uV
Band 3:	12 - 17 Mcs	6 - 4 uV
Band 4:	16 - 24 Mcs	10 - 3 uV

Sensitivity

CONCLUSION
The radio receives the local broadcast stations easily. The three short wave bands also have a good sensitivity. The tuning is a little quick, with the small tuning knob. This is despite the two top bands being expanded, and having a flywheel on the tuning knob. When shut up in the heavy steel case, it is a very rugged little radio.

Circuit

REFERENCES
A.E.W.1 Working Instructions and Service Bulletin, Z1/ZA 3006

Copyright
Ray Robinson

INDEX