PCR Receiver

 This ex-army superhet made by Philips Lamps rather than its usual manufacturer, Pye, was the type often used for general entertainment in the forces, such as in the NAAFI, and said by some to have been supplied to resistance networks. If the latter is true then communication must have been by speech or MCW because this set has no BFO for resolving CW but, I believe a similar model, the "PTR" was fitted with a BFO and therefore was more useful for covert use. The PCR was very popular in the government surplus marketplace for home use as, just after the war, domestic receivers were hard to come by at a sensible price. This receiver would have cost a buyer under £8, about half the price of a shop-bought set.

A weakness is the dial. In this example the last owner gave up and rather than correct any defficiencies fitted an old maths protractor in its place, thus making proper restoration quite difficult. What remains of the dial marking is in white paint above the tone control and wavechange switch and may have used a radioactive isotope to fluoresce from the dial lamp illumination. In that case the markings may have degraded over the years or possibly were erased if the last owner attempted to cleal the dial. The set usually came with its matching power supply in a separate box.

This example, an early ZA26707, has some modifications.. for example, a Belling Lee aerial socket and a hole in the panel above this. There were several versions of this receiver of which this is the earliest, without a model number following "P.C.R." and with a built-in loudspeaker.

 

 The interior and the valves in this example are in new condition, but why the hole cut in the front panel I wonder?

 

 

 When I removed the receiver from its case I found most of the valves were loose because the valveholders are cheap paxolin types rather than the usual black bakelite and don't grip the valve pins very well, especially whilst moving through the UK postal service. The loudspeaker transformer is a Radiospares part and next to this is an HT choke made from the energising coil from an old loudspeaker. The choke may have been removed from the original speaker, as the one fitted now is much newer than the date of the set's manufacture.

 

 

 

 Stuck to the inside of the case is this label. The valves fitted in this example are:-

RF amp EF39, Frequency Changer ECH35, 1st IF amp EF39, 2nd IF amp EF39, Detector, AVC and Audio amp OM4, Output CV1052.

The OM4 is similar to the EBC33 and the CV1052 an EL32. All, apart from the ECH35, look brand new.

 Two power units were available. One for battery operation and this the mains version, the ZA26706.

 

 The shiny black metal valve is a 5Z4 rectifier

 

 It looks like the smoothing condenser was replaced, probably back in the 1950s? Also the power connector has been replaced by a choc block. The power lead is rubber insulated under cotton covering and has perished and it's very likely the mains transformer is a replacement.

 

The PCR sets were made late in WW2, from April 1944 to December 1945 with several re-manufactured by the REME workshop in Newark as well as by a few UK military radio suppliers in the 1950s and 60s.

 This particular example is the P.C.R. (Portable Communications Receiver) and covers three wavebands, two of which were displayed on the (now missing) dial in traditional metres and the other in Mc/s. Long 2100m-850m, Medium 570m-190m and Short Waves 5.8Mc/s-18Mc/s.

The PCR1 covered the same bands; the PCR2 had a slightly larger shortwave band 6Mc/s-22Mc/s, and the PCR3 dropped the long waveband and instead provided medium and two short wavebands, 2.3Mc/s-7.3Mc/s and 7Mc/s-23Mc/s. Later models used an external loudspeaker and the IF used in all versions of the receiver is 465Kc/s.

 

This is the circuit diagram of the PCR1 (click it to see a larger picture)

 Compare with the PCR2 and Compare with the PCR3

 

 This is the circuit diagram for the P.C.R. mains power supply, known as "Supply Unit, Rectifier No.17" (click to see the PDF)

Note the complicated primary winding arrangement which is slightly unusual as it caters for a very wide range of mains voltages and that strange looking connector labelled "SK1" which is similar to the type used in the WS No.19 for connecting headphones etc . It comprised a pair of flying leads terminated in bulky rubber sheaths that could be pulled apart. It's reported frequently that the PCR set was designed by the same Pye engineers that designed the 19 set and they presumably thought that this odd connector was better (cheaper and used less materials) than fixed sockets and a connecting lead.

Now to tackle that awful replacement protractor dial...

Below, with the dial parts removed.

 

 There's a very tight fit between the tuning condenser and the front panel. So close that the screws securing the front panel to the chassis need to be removed to allow the plastic cover to be detached, followed by the dial pointer which will be coloured white instead of black.

 

 

 

 This is the old replacement dial. Someone took a long time to do this modification. The protractor is drilled and fastened to the old perspex using small copper rivets.

There are several possible reasons this change was carried out. The most likely is the old lettering which was on the inside of the plastic just deteriorated and fell off. Maybe an attempt was made to clean things and the lettering was removed together with the dirt, or maybe the old lettering was radioactive and was removed for reasons of safety? I could test what remains in the lower engravings...

 

 

 This is the new dial. I made this using a photograph of an original PCR dial kindly supplied by Paul Taylor.

I measured the mounting points and critical sizes and printed the new dial so it was exactly the same size and shape as the original. My version of the receiver had the dial printed on the rear of the front perspex panel but all traces of this had been removed before the protractor was fitted. The rear metal plate was pinted off-white to reflect light from the dial lamps through the perspex. Also on the perspex plate were engraved the settings for the tone and wavechange controls.

As you can see the new dial is now glued to the metal back plate.

 Below old and new perspex panels. The old panel has two unnecessary fittings. There's a brass bush tapped 6BA so the panel can be accurately positioned and below this a brass bush that slides over the tuning condenser spindle. The perspex can be tapped 6BA and a clearance hole drilled instead of a brass bush. The semi-circle is there to allow the tuning flywheel to fit.

 

 

 

 

 

 

 

 In order to reposition the tone and wavechange pointers so they are nearer the new dial rather than the rear of the perspex, two changes are needed.

The two pointers are repositioned further back on the switch spindles which requires the lower flanges of the back plate to be cut back by about 10mm.

 

 Above the new dial in place. The various securing screws will be fitted once the dial is positioned correctly. I'll need to figure out what to do with the hole between the speaker and the dial. Maybe a rheostat for the dial lamps?

Below... before and after.

 

 Now that the dial has been sorted out I can test the receiver. Looking under the chassis I can see that one connection to the (new?) toggle switch is hanging off and the other goes to the HT line. It's possible someone's been fault-finding long after the modifications were carried out? Maybe suspecting an HT problem and there's certainly an HT problem because the lead between the power supply and the receiver is completely perished with an inch of HT and heater wires completely devoid of any insulation. Another thing I found is the (new) Belling Lee socket is not for an aerial because it goes to the live side of the volume control via a resistor so it's either an input for something or a high impedance output.

One idea is to relocate the power supply components to the free chassis space (the chassis is even drilled for a rectifier valve socket) but that would completely alter the design of the set so I'll probably just fit a new power lead. All the original 1944 condensers are still fitted so as a minimum I'll need to change some critical ones, starting with C21 the EL32 grid coupling condenser. A variac feed to the PSU will be a good idea also.

Most of the rubber-covered connections under and above the chassis are perished so swapping these for new will be prudent. This is a common problem with WW2 equipments such as early R1155 receivers which frequently emit plumes of smoke if not seen to. Lots of sets, like many WS19 particularly later models, or those that have been rescued by REME workshops, are OK in this respect as plastic insulated wire was used. This PCR must have been disposed of soon after WW2 because it was an early version.

 

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