Repair, Restoration or Oily Rag?

As the title suggests, here at Wartime Sounds I favour my radios in what is often called an "Oily Rag" condition, that is to say those which are in a fundamentally original state, preferably with original valves and Chassis components but which is made electrically sound and safe, and while I agree that full restorations have their place in the vintage radio world, I strongly believe the only way for a radio to maintain a sense of history (and the Civilian Wartime Receiver has plenty of that) is for it to be preserved as much as possible in its original condition. What I think they also call a “sensitive” restoration! Please bear in mind, as with all radio repairs or restorations; 

Electrical safety is paramount and any work should only be under taken with great care and carried out by a competent person.

My “Oily Rag” Restoration

Firstly let’s get this clear from the outset, when I say “oily rag”, I do not mean that all it gets is a quick wipe over with an old rag and then used!, far from it, in fact the oily rag does not go anywhere near the restoration even in dealing with the cabinet, which always seems to present itself with a challenge as I will explain later! Well perhaps I tell a small porky, a rag is used in the final cleaning of the finished receiver but nothing more! The essence of the “oily rag” restoration though is to try somehow to capture its history and the journey it has been through and with that in mind that’s how I start my “sensitive” restorations.

Initial Restoration Work Inspection.

Once I have got my receiver on the bench I first like to make a written list of what work might be required and then after removing the chassis from the cabinet, continue with a more detailed visual inspection of what work I might need to do. Experience has taught me over the years with the Civilian Wartime receiver, never to just plug it in and see what happens. Nine times out of ten, there is always plenty wrong with them and most of the receivers I have owned (and seen), they all seem not to have “weathered” the age of time very well at all. Things like the HT smoothing capacitors for instance, are usually found to be faulty or on the verge of going faulty and if not, have been quite often replaced somewhere in its early past, which again can be a potential source or cause of problems if not done correctly. The negative wiring to the three separate smoothing capacitors on the AC mains receivers is not a straight forward conventional to earth (chassis) arrangement as one might think, with one out of the three capacitors negative returns being used to provide a negative bias voltage from the HT mains transformer instead. A mistake I have seen done several times, usually due to the fact that they are all situated together under one bracket and people, wrongly assuming where the wiring goes with some very strange results. Another favourite failing of these receivers is its wiring and its general degrading and perishing of the rubber coated wiring loom. Not all manufacturers suffered with this but in my experience more did than did not. It is also useful at this stage is to check (“megger”) the mains transformer insulation (AC Mains version), although usually a very reliable part of the radio, I have had them fail and again cause some very strange symptoms, not least to run hotter than it should and of course the testing is also for your future peace of mind and safety as well. Finally then armed with my visual inspection findings list, which also will include any of the other common known failings as well such as the wax paper capacitors that so often go leaky, any potential suspect resistors to check or any known faults that I am already aware of, I am then (hopefully!) aware of the task ahead and what is needed to start my restoration of the receiver and what is potentially involved in bringing it up to specification before anything else is done or even switched on. Again this is my personal way of doing things and I know many would argue differently but I find this works for me. The inspection is similar for both the AC mains version and the Battery model.

The Restoration Process

Armed with my list I normally start with the cabinet first, no real reason although I tend to find that it helps me with my vision of how the finished receiver will look and the history it holds and also to stop further degrading.

Cabinets

Unfortunately the cabinet can quite often prove one of the most challenging parts of the restoration process as the Civilian Wartime receiver’s Pine cabinet seems to suffer greatly from deterioration through ageing, so attention to this is always a priority. As a standard I now start with having the cabinet wood worm treated as the pine or glue used in the cabinet’s construction seems to be a wood worm’s favourite meal! Funnily enough as a side note, for some unknown reason, nearly all my Bush (U1) receivers I have had or I have seen have been infected to some degree. As I said before, don’t know why this is but well worth bearing in mind and treating just in case. Once it has been treated (and left for a period of time) I tend to lightly sand the cabinet and apply a thin coating of clear varnish to the cabinet both to the inner as well as the outer. I know some might say that the original receiver wasn’t varnished but again though my experience, most Civilian Wartime receiver’s cabinets are so bad that this method of treating and varnishing after seems to help preserve them with good results, again just my opinion.

A final note under the cabinet heading, do look inside the cabinet carefully as several cabinets I have in my collection have makers marks inside. The most noticeable one being the GRLtd 1944 stamp, standing for the Gordon Russell Cabinet Manufacturers Ltd. Gordon Russell was the famous designer of the Wartime “Utility” range of furniture and was appointed by the Government to lead the design panel to set up the manufacturer of the Utility furniture, his company also exclusively produced cabinets only for Murphy Radio.

Seen here is the Gordon Russell Cabinet and Makers Stamp.   

As you can see unfortunately the cabinet is not in a very good condition.

Chassis

After cleaning the Chassis thoroughly with a clean brush, preferably in the open air, I then start to replace the wiring as necessary, trying to use similar coloured cable as was used originally, before moving to replacing components. Be particularly careful both with the cleaning and the wiring replacement not to disturb or damage any of the coils and to re-route cabling, where possible back to near original position as possible. Once all suspect or required components are replaced, I then move on to cleaning or replacing other parts on the chassis such as the On / Off switch, Volume Control and the Tuning Capacitor bearings and mountings. Finally before starting to start the receiver up and dealing with any additional faults or performance issues that might be present; I then replace the mains lead with a current British standard 3 core cable and plug, earthing the chassis as a standard.

 Pictured here is the restoration of a U7 (Murphy). This receiver has the Gordon Russell cabinet dated 1944, so one would assume that this was an early production receiver. This particular cabinet has unfortunately not aged well, as can be seen but to be honest I think that adds to its charm and of course as I said right at the start, its history!

I have not listed all what I did to it but hopefully these limited pictures will tell the story.                       

Also I have listed separately later the common faults that I have encountered along the way.

Final Alignment and Testing

Finally once the receiver is now working and functioning, hopefully well then we move on to the final stage of alignment and soak testing. I try to soak test or run my receivers for as long as I can but with a minimum of at least a week (equating to about 24hrs continual running)

 Listed below is the service sheet guidance set out for the Civilian Wartime receiver alignment. Although alignment can be a little daunting to the beginner, the Civilian Wartime receiver alignment is quite straight forward and simple and it is also fair to say that the receiver’s design is also quite a “forgiving” one even if not quite done correctly, with good performance still achieved.  

 Workshop Footnote:  Always refer to the modifications sheets before attempting any alignment as although the IF frequency was set at 460 kHz as standard some manufacturers, in practice used slightly different frequencies, presumably in using up old shelf stock of components. An example of this is the Cossor U3 AC version who’s IF frequency is 462.5 kHz.

Suggested Alignment Method Used on the Trader Sheet

IF.  Connect signal generator (via 0.01uf) to top cap of V1 (Ech35) and earth. Turn gang to min and Volume control to max. Feed in 460 khz (652.1m) signal. Adjust L5, L6, L7 and L8 for maximum output.

RF & Oscillator.  Set gang to max. Curser line on disc should coincide with calibration mark on scale (near 550m) If not adjust curser line on disc. Attach signal generator (via 0.0002uf) to A1 & earth. Tune to 220m (calibration mark) Feed in 220m (1362 khz) signal & adjust C22 & C20 for maximum Output. Feed in 500m (600 khz) signal and adjust L2 & L3 for maximum.                                        

Suggested Alignment and Calibration Used on the Radio Marketing Service Engineer Sheet 

Set the dial so that the cursor line coincides with the mark at the top left hand side of the scale when the gang is at maximum.  

IF. With Aerial & Earth shorted and Volume control to max. Inject a 460 khz signal via (0.01uf) to top cap of V1 (Ech35) and earth. Adjust the 4 IF trimmers for maximum output (Avo meter across the speaker)                                                    

RF & Oscillator.  Remove Aerial / earth short. Inject 220m (1362 khz) signal via a dummy Aerial to Aerial socket. Tune cursor to calibration mark. Adjust C22 & C20 (Trimmer 1 & Trimmer 2) for maximum. Tune to 500m, inject 500m (600 khz) signal and adjust iron cores of Oscillator and Aerial coils (L2 & L3).

Workshop Footnote:  Always do the IF first and set the Avo or Output meter to the Ac 2.5v / 3v range for best results. I tend to do both methods, acting as a double check to its performance, again just me!

Dial and Dial Drive Mechanism

Shown here is the dial mechanism and various manufacturers’ style of dials, dial plates and fixing used.

Note the two alignment markers circled in red, often mistaken for scratches or blemishes in construction.

Common Faults


Listed here are some of my faults that I have experienced during my restorations. I will try to keep the technical content to a minimum and as already has been stated, with all radio repair or restorations; electrical safety is paramount and should only be under taken with great care and carried out by a competent person. Finally of course the fault symptoms listed here can vary greatly and should only be used as a starting point to further testing or fault finding.

C10 (0.1uf) Capacitor – De-coupling of grid V2                                                                                                                                                                                                                                                                                Symptoms: O/C – Poor performance / S/C – Possibly no output

C14 (0.005uf) Capacitor – AF coupling to V3                                                                                                                                                                                                                                                                          Symptoms: O/C – No output / S/C – Av Instability

C15 (0.005uf) Capacitor – Tone Correction (across speaker)                                                                                                                                                                                                                                                    Symptoms: O/C – Poor tone / S/C – No output

C2 (0.005uf) & C7 (0.1uf) Capacitors – AVC De-coupling                                                                                                                                                                                                                                                            Symptoms: Poor performance or reduced gain

HT Smoothing Capacitors (8uf) – C16 negative should be wired to the HT Centre tap not chassis as the other two are.                                                                                                                    Symptoms: Hum and strange symptoms  

R7 (1M5R) & R8 (4M7R) Resistors – AVC System                                                                                                                                                                                                                                                                            Symptoms: O/C or high resistance – Poor performance or reduced gain

BVA Valves – Through experience I have found that the original fitted BVA manufactured valves are quite often low emission or poor performance. If you find your receiver is showing poor performance and or strange symptoms, it may well be worth substituting the valves with known good, after checking any other work you have done first of course!

IF Screening Cans – Securing nuts located under the Chassis (poor earthing)                                                                                                                                                                                                                Symptoms: IF Instability and drifting

On / Off Toggle Switch – Quite often slow or sticking pole mechanism to switch across causing fault symptoms ranging from arcing to completely dead. (Footnote: I generally change as a matter of course for safety improvement reasons)

MR1 (Wx6 Westector) – Detector                                                                                                                                                                                                                                                                                                            Symptoms: High Impedance or O/C – Poor performance or no reception

Workshop Footnote: O/C means Open circuit and S/C means short or” leaky”

                                                                                                                Ac Valve Readings                                                                                 Battery Valve Readings


Finishing Touches - Labelling and Cabinet Decal

Back Panel and Label (AC Mains)

Cabinet Top Label (Both)


Other Labels Found on the Wartime Civilian Receiver (U number)               

Other Labels Found on the Wartime Civilian Receiver (Guarantee or Dealer Warranty)                                  

Other Labels Found on the Wartime Civilian Receiver (Assembly and Inspection Tags

Box and Transportation


Just a few of the Restored Collection

From left to right - U2 (Ekco), U1 (Bush), U20 (McMichael) and one of my favourite restorations, the U9 (Pye)

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