Marconi CR100 mounted in a home constructed handling frame which protects the chassis in any position while it is receiving attention on the bench.

PSEI Trophy-8 has paxolin valve sockets which cause earthing problems for the solder tags, as shown here on the RHS mounting screw sandwiched between the
paxolin and the chassis - look carefully!

GEC BRT400K showing a re-soldered chassis seam. Sprung joints are very common indeed on this model.

Eddystone EA12 uses nylon dialdrive pulleys which swell over time due to water absorption. The result is excessive pointer travel from end to end.

Marconi CR100 centrally captivated band change cord, which proved extremely difficult to replace. Look carefully to see how the cord enters the little metal drum in two places. It’s very difficult indeed to assemble it correctly.

GEC BRT400K steel dialdrive wire runs in greased brass guides. Early variants (without front panel handles or dial lock) used pulleys. Dial lamps have been removed for clarity.

British Army R209 Mk2 pressure testing set-up, showing the desiccator which has to be temporarily replaced by a purging bung for this operation. When all is well, the manometer shows unchanging pressure after initial pumping.

National NC100XA dialdrive endstop plate shown standing vertically with one bevelled corner visible. This is a very poor design which required careful filing to operate correctly.

KW202 tuning capacitor, showing its non-standard glued plastic cover which considerably reduces VFO drift. Also shown is the Kokusai 455kHz SSB mechanical filter.

Murphy B40D tuning gang, with its fragile ceramic shaft which snaps if the radio has been dropped. This is a scrap set, hence the dead leaf on the LO valve socket!

Racal RA17L filmstrip scale, a thoroughly well engineered solution. Dial bulb removed for clarity. The big disc is the MHz display dial. Its outer knurling bites the dial lock brakeshoe rubber when required.

GEC BRT400K SRBP tag board, now patched with an FR4 plate as is commonly necessary on this model.

Murphy B40D needs air to enter this very heavy radio from underneath. The tuning chain can be seen wound round its small drive sprocket which can be seen through the big hole in the casting.

Marconi Atalanta panel damage caused by botched knob removal, a common problem due to poor knob design.

Kwikfyl crayons, a tin of Humbrol enamel and the pointed application tool used by the writer.

Philips EFM1, a rare magic eye with integral AGC-controlled AF pentode on the problematic CT8 base. Also shown is an RCA 7360 beam-deflection valve.

Eddystone S770R/1 special RF valve socket with two turned pins instead of the standard stamped items.

British Army R209 Mk2 desiccator cartridge, with its rubber O-ring seal. Shown with home made pressure testing adaptor which includes the Schrader valve used to prove sealing.

Collins R-390A bellows coupler employed to turn the BFO shaft whilst accommodating squeeze & stretch. At the bottom of this picture are two Sprague Black Tubular (BT) capacitors which must be replaced. To the left of them is a Vitamin-Q which a reliable type.

Hand tools most commonly used by the writer in his own workshop for radio restoration work. Yes, the roll of kitchen towel is there deliberately! The chassis to the left is a Marconi CR100/B28.

Marconi CR100 is a very properly engineered radio which has an ill-deserved reputation for drift and unreliability. The little subchassis standing up to the left of the gang is the noise limiter, with its toggleswitch.

Marconi CR100 showing ceramic pillars used to replace original stud-ended tubular capacitors. A modern polyester capacitor is strapped across the pillar from top to bottom, to replicate the original earthing arrangement.

Marconi CR100 band change shaft is split to allow the flexibility necessary on mid production chassis such as this one. The misalignment is due to a design or manufacturing error which was fixed in late production models.

Marconi CR100 replacement mode switch is a very tight fit. Note use of wire identifier tags and ink legends on the switch wafer.

Marconi CR100 underside view showing absence of BFO cover, discarded at some time due to overcrowding. This chassis has even gaps everywhere: a good layout.

Eddystone EA12 showing two of these receivers, both unrestored but in basically good condition.

National NC100XA interior view of the catacomb casting. Centre top biscuit removed, to show stator contacts visible through the shaped hole. Rack & pinion drive mechanism to the right of the carriage.
Notice the mighty guide bar to the left of the carriage!

Eddystone S358X has a very unreliable single pole mains switch which can fail to break. B40s use the same family of switch: a potential fire & safety hazard.

GEC BRT400 Mk1 IFT carries 240VDC between the RHS (secondary) bobbin and its overwinding, shown here. There is no gap and no meaningful insulation so flashovers are common, especially in damp conditions. Notice the Philips beehive trimmer, a type prone to short circuits. Later BRT400D IFTs had mica fixed capacitors but kept the beehives.

Eddystone EA12 has an unreliable mains connector, relying on a single-sided blade to connect the earth.

GEC BRT400D with typical decomposing bitumen-impregnated Iron HT components, a very common cosmetic problem on GEC and Philips sets - and also on the RCA AR-8516L.

Marconi CR100 grid caps rewired in 16/0.2mm PVC for the LO (left), and RG316/U PTFE coax cable for the mixer (right). Also shows Hellermann insulating sleeves.

EKCO R1155A original screened cable fitted with a new 16/0.2mm PVC inner, to preserve appearances. The new PVC insulation can be seen next to the grid cap.

Philips 6H8MG, a rare double-diode pentode used in the unusual AME 7G1680BA receiver. The nearest sensible equivalent is the 6B8 from the USA

This PSEI Trophy-8 uses Meccano chain drive. One example has been seen with a rubber belt instead. Probably the writer’s set was modified at some time.

PSEI Trophy-8 chassis design gives plenty of room to its RF box. Note the retrofit HT fuse mounted by the output transformer, and the new mains cable, fitted by the writer. These modifications are intended to promote safety.

PSEI Trophy-8 front panel shows the barometer glass. Note the circular legend rings missing from two controls.

PSEI Trophy-8 general view, showing the cabinet and the unusually tidy chassis topside layout. Notice the huge gold-metallized 6TH8G triode-hexode mixer.

GE compactron type 6AS11 contains two signal triodes and an output beam tetrode, shown alongside a 5749/6BA6W pentode.

Acorn glass triode which seats into this type of special ceramic socket for the Hallicrafters S36 receiver. Also shown is a later, more advanced 6CW4 nuvistor triode which was in volume production for USA TVs for a couple of years.
These were very high technology devices employing ceramic/metal seals.

Eddystone EA12 uses blobby solder joints, as with this resistor on the rear panel. These joints can be found open circuit sometimes.

Eddystone EA12 uses many cheap and nasty components such as these troublesome grey Dubilier resistors. Notice again, the horrible original solder joints.

Lozenge mica capacitors often go leaky. Some American types ooze sticky froth where the leadout wires emerge from the plastic casing when a high DC voltage is applied. This is a sure indication of trouble.

Hunts “Mouldseal” moulded capacitors like these, are extremely inclined to crack open and go leaky or open circuit. The writer’s policy is to replace them on sight!

Cornell-Dubilier bathtub block containing 2 x 100nF/400V oil filled paper capacitors.

EAC R-390A IF unit has Sprague BT capacitors with colour-coded rings. They are very unreliable, and a fire hazard.

Eddystone EA12 uses cheap red, yellow & black Plessey electrolytics. These often dry out and lose value.

Collins mechanical filters, all 455kHz: 12kHz for 75A-4, 2.1kHz for early KWM-2, 500Hz for 75A-3 and a current high performance 12-pole SSB filter.

R-390A mechanical filters from all three manufacturers who made them: Collins, Dittmore-Freimuth and Whitewater Electronics. Some ceramic filters from Clevite were also fitted - not shown here. Beware Collins round-emblem filters which rattle due to rotten foam inside.

British Army R209 Mk2 is a very pleasant small HF receiver which works very well indeed. Design quality was excellent. Production was by MEL o/b/o Philips.

Largely Marconi workshop instrumentation, the most useful being the TF1041C VTVM in the foreground and the two TF144H signal generators. The oscilloscope is a Cossor CDU150. Note the prominent emergency STOP switch.

Megger insulation tester type 70158, used on its 500V range in the UK where the nominal mains voltage is 230VAC. Great care is needed when in use!

The writer, Chris Parry photographed in March 2002.

National NC100XA is a handsome radio, but the great height of the tuning knob makes it tiring to operate.

National NC100XA on the LF band of its coverage. Most of the radio electronic circuits are openly accessible. This side of the chassis is to the original design.

National NC100XA on the HF band of its coverage. This switch position reveals the PSU & AF sections, all non-original due to wiring problems and missing Iron components.

National NC100XA topside view, showing a generally tidy layout using the old style HRO crystal filter. The PSU and audio strip is totally non-original, necessary because of rotten wiring and missing Iron components.

Marconi CR100 operated well under battle conditions as its knobs are large and widely spaced. The RIS connector has been replaced by an S-meter, as is common.

KW202 & Heathkit SB-300 competed for the radio amateur’s money, and both were competent designs.

Heathkit SB-300 topside, extremely neat and tidy. This example has three crystal filters, and a full set of six range conversion crystals. There is one compactron. The VFO came from TRW, and is very competent indeed.

Heathkit SB-300 underside, which is a bit too crowded at the lower left around the power supply.

KW202 topside, showing lots of wires. The vertical PCB in the foreground is the calibrator, and at rear left is the solid state notch & Q-multiplier board. Notice the writer’s black plastic cover over the VFO capacitor, to reduce drift. Also notice the yellow Kapton tape covering a hole on top of the VFO box. This is directly below the lid finger hole. It stops unwanted rubbish getting into the VFO.

KW202 underside. The two big series resistors feeding the VFO are exactly as fitted originally. Notice how the PCB groundplane is broken up by lots of heater tracking. This causes excessive hum in the audio.

EKCO R1155A with the late dialdrive is a truly excellent receiver, and very light in weight. A previous owner has removed the DF facilities. This example has been much hacked-about over the years, and is typical of most survivors of this model.

EKCO R1155A RF interference trap canister supported only by a small bent Aluminium bracket. It nevertheless proved strong enough to withstand the shock, bump and vibration in a Lancaster bomber aircraft.

EKCO R1155A has a clever coilbox which allows access from 2 orthogonal faces, to improve serviceability.

EKCO R1155A topside is very crowded even though all the DF hardware has been removed from this example.

EKCO R1155A underside, showing plastic wire-ended capacitors in place of the stud-ended originals. The new output transformer can be seen clearly.

Eddystone S770R/1 is a handsome set, very heavy for its size. It was made for many years and sold well because there was little competition.

Eddystone EA12 variable selectivity. The ¼” shaft carries three cams & levers which change the position of one winding inside each 100kHz IFT. The red Hunts dipped capacitors shown here are usually OK, but beware these grey Dubilier resistors.

Eddystone S770R/1 is extremely hard to work on, as access is very poor indeed. This one had to be dismantled for repairs to the IF and AF modules.

Eddystone S770R/1 has some heroic engineering underneath! The antenna trimmer shaft leaves the RF unit at a rakish angle to reach the front panel via two UJs.

Eddystone S770R/1 showing a lot of valves crammed into the space available, a neatly executed design. Inadequate ventilation means this set is a hot runner.

This Eddystone S770R/1 audio unit is actually taken from an S770U. Many new bits are fitted, as a lot of the original components were cooked.

Eddystone S770R/1 RF strip originally fitted with three EF95s, now has a 6AJ5 variable-µ RF amplifier. Selection is needed to choose the right sample because not all 6AJ5s have a suitable transfer characteristic. TungSol examples work fine here.

Eddystone EA12 uses logarithmic compensation of scale linearity. Various covers go over this assembly. Notice the top quality Philips beehive trimmers, which have proper machined leadscrews for a change. The writer wonders why GEC did not use these in the BRT400.

Eddystone EA12 underside has a very neat layout, especially considering all the many user features.

Eddystone EA12 chassis topside, with an FR4 plate temporarily covering the loudspeaker to protect it from damage during servicing.

Eddystone EA12 uses fragile rear panel terminals which have no physical protection. Typical Eddystone, sadly.

Eddystone EA12 uses small coils and SRBP switch wafers which were no doubt cheap, but they reduce the unloaded Q significantly.

GEC BRT400K has a new loom fitted along the power supply sidewall, shown at the bottom of this photo. The original loom was fried due to shorts somewhere in the bulb wiring, which is a common fault.

GEC BRT400K is a handsome radio but heavy, and the chassis is very inclined to crack and develop other structural failures. Early BRT400s lacked front panel handles and calibrator but went up to 33MHz, and not all late sets had the calibrator.

GEC BRT400K has deep RF compartments which are hard to work inside. Most chassis seams are riveted & soldered, but the RF bulkheads are riveted only.

GEC BRT400K chassis topside view showing a new mains transformer cover. This set started as a BRT402K, and was later given the correct table cabinet to convert it into a BRT400K. Note Kapton tape over the IFT holes, to keep dirt out. Beehive trimmers make this a very sensible precaution. Notice the adaptor plates used to fit B7G valves into chassis holes originally used for B8G types.

GEC BRT400K chassis underside view showing the set as easier to work on than is actually the case. Notice the heavy metal cover over the LO compartment, and also notice the BFO cover at the top right. Equally notice the lack of any proper covers over the aerial, RF amplifier and mixer sections of the bandchange compartment.

GEC BRT400K audio/AGC section is almost the ultimate in valve radio design. In the opinion of this writer only the earlier BRT400D/E was better, care of a posh
KT81 beam tetrode output valve rather than a cheaper EL84.

Telefunken E127KW/4 panel has a large half-moon dial. The knob pushes & pulls to give two speeds.

Telefunken E127KW/4 chassis topside view. Steel perimeter frame is an integral part of this radio.

Telefunken E127KW/4 has this unusual tapped power resistor.

Telefunken E127KW/4 RF unit is quite compact. Extremely good quality components throughout.

Telefunken E127KW/4 IF unit uses surprisingly simple distributed LC & crystal filtering.

Telefunken E127KW/4 chassis underside view is conventional, with large pressed
metal screening covers.

Telefunken E127KW/4 dialplate is in cast Aluminium, lit by four bulbs to give unusually bright illumination.

Telefunken E127KW/4 dial is a beautiful piece of work, allowing surprisingly accurate and repeatable frequency readout. Notice the lenticular magnifier.

British Army R209 Mk2 chassis topside view, with two modules removed to highlight the plug-in construction.

British Army R209 Mk2 module, showing IFT and battery valve.

British Army R209 Mk2 chassis underside shows easy accessibility. The heavily screened box on the left contains the vibrator. The RF box is on the right.

Murphy B40D is a strange-looking but handsome set which is also unusual in its engineering. The massive cast front panel is not as strong as it looks: beware!

Murphy AP100335 is an RN LF + HF receiver designated type 618, designed for smaller vessels. It is very different from the B40, but still unconventional. As yet unrestored. Pye made an inferior direct equivalent to this receiver, selling as the
Rees-Mace type CAT.

Murphy B40D with its PSU/AF tray slid back slightly, to highlight the cast Aluminium construction.

Murphy B40D IF side, also showing the PSU and audio valves. The modules separate quickly and easily.

Racal RA17L is an ex-RN radio with especially good ergonomics. This is one design that works much better than its on-paper performance would indicate.

Racal RA117 + RA218 ISB adaptor, fitted with spurious front panel labels.
Complete and fully functional. More complex but cleverer than the RA17L, and capable of operating with an early synthesizer called a “Racalator”.

Racal RA17L bottom covers must be fitted tightly and with clean & bright fingerstock to reduce spurii.

Racal RA17L topside. The chassis is deeper than on other commonly seen radios. All very neat, but module removal is certainly not straightforward.

Racal RA17L underside view, showing cast compartments. Critical filters live under the L-shaped covers left in position here. The box at the bottom right contains the antenna attenuator switch.

Two S130Ps: LHS is a balloon-top Cossor, RHS is a GEC in shouldered glass. They have very different regulation behaviours. Not all GEC S130Ps glow orange. Notice the wire mesh priming electrode inside the LHS valve.

Racal RA17 original prototype, as displayed for several years in the foyer of the Racal HQ in Bracknell, UK. Note the choice of knobs.

Racal RA17 original prototype. The left and right are NOT two separate castings. Difficult problems of spurii led to the original single casting being bandsawed into two completely separate halves. Look carefully and you will see the sawcut! This broke the path of the earth current, enabling correct performance to be achieved.

Racal RA17 prototype, all pretty much as would be expected apart from the 5Z4G rectifier, which must have worked too hard in this application! The famous sawcut is in evidence from left to right of the chassis, just below halfway down.

Racal RA17 prototype underside, showing a single screening plate with the large retrospective bandsawed cut-out to achieve correct grounding and proper routing of earth currents. Production RA17s had a more complicated screening arrangement.

AWA CR-6A and CR-6B radios, one with the correct table cabinet and the other with the optional multi-channel unit. Somewhat smaller and lighter then the norm, these are among the writer’s favourite radios.

AWA CR-6B chassis topside, all very open and straightforward. This radio has the optional multi-channel unit fitted. The Cadmium plating is in good condition and the chassis looks much as it would have done when new

AWA CR-6B RF unit showing the demountable construction and the use of topclass Philips beehive trimmers having proper leadscrew adjusters. Why did not more manufacturers use these components? The variable capacitor shows its ceramic shaft in this photo.

AWA CR-6B pre-adjusted demountable IF block filter, also showing the optional six position multi-channel module. This perfectly sound idea was next seen years later in the Pye Cambridge mobile radiotelephone.

AWA CR-6B chassis underside showing the proper fitted cover beneath the RF unit to stop draughts and promote frequency stability. The mighty bandchange roller chain is rather as seen in the RCA AR-8516L - but the AWA implementation works better. The selectivity wafer switch at the top of this photo forms part of the IF block filter module. Notice how easy this set is to work on - very intelligent design.

AWA CR-6B close-up of the selectivity switch, carried on a metal bracket which also accommodates the five 100kHz IF coils. No nasty micas to drift away from the correct values! Notice how the main radio chassis is fitted with Mullard tubular polyester capacitors. These are about the only type still considered reliable some fifty years after they were made.

KW2000E is a very handsome transceiver. This is the final model, which tunes in 500kHz segments. It has RIT, TIT etc and good VOX facilities. It came to be
known as the “E for Expensive” variant!

KW2000E interior, showing conventional chassis construction and at lower right, the dropper for the 150V zener HT regulator. An 0A2 neon had been fitted to earlier models. The large cylindrical can is the Kokusai mechanical filter.

KW2000E vertical FR4 PCB was termed the “KW Vox Box”. It may perhaps have been standard fit instead of an option as on earlier models. The oversize washer on the PCB corner was fitted by the writer to protect transformer IFT5 when the chassis is being handled on the bench. The large B9A valve fitted with the spring retainer is the ECL82 for audio output.

KW2000E rear panel, showing the small Painton multi-way connector which carries raw mains, +1000V HT off load, and transistor supply voltages from the external PSU box. The metal shell of the mating connector is not even grounded. This is extremely dangerous equipment design. Notice the absence of a “Danger High Voltage” warning label. There should certainly be one!

KW2000E showing plastic boxes added by the writer to improve frequency stability and reduce dust ingress. Notice the yellow Kapton tape covering a hole on the top of the VFO module. This aperture is directly below the finger-hole in the cabinet top cover. A delicate Philips beehive trimmer lies directly underneath. The tape stops debris falling into the VFO, and also captivates the bulb wiring.

GEC BRT400D showing the desirable fan modification. This model otherwise gets far too hot to be reliable. This version predates the BRT400K. Three B8G valves, an octal and three B7Gs are shown in this photo. The unusual B7G valvecans are original to this radio.

British Army R209 Mk2 power unit, showing the solid-state vibrator. It works very well, but forces the radio supply polarity to be negative earth. The original WICO mechanical vibrator made no internal connection to its can, so did not cause this problem.

RCA AR-88D chassis underside, showing excellent screening arrangements. All rotary switches have ceramic wafers like those shown here. The multisection smoothing block is being rebuilt using 3 pairs of 10µF/450V/105°C high reliability electrolytics in series, each capacitor strapped by a 220kΩ TR6 metal oxide voltage balancing resistor. This gives 5µF/900V/105°C per section instead of 4µF originally, with a total effective bleed resistance of 147kΩ.