This is my second R1475 as received

An abandoned project?

 

 

 

 

 

 

 

 

 

 A rather nice undamaged plastic dial cover was included. The condition of the chassis is about the same as mine but with less corrosion present. I'll finish off derusting it before reassembly. The guard receiver (out of focus) is all there but the main dial assembly has been worn at the LF end and will benefit from some signwriting or re-labelling. Touch wood.. everything looks present... and having got an assembled receiver putting the second back together should be straightforward.

Last night I finished off the main chassis which was going rusty (again?). I then sorted out the guard receiver chassis on my earlier R1475 by copying the dimensions and layout of the one in the box of bits.

At this point I realised that the last owner had disassembled everything and had painted the front panels but had probably intended to clean up the chassis components, and no doubt go through all the components and replace any that had gone bad. I went through the larger bits and wire brushed the ones that needed rust etc removing. During this process I noticed that some parts seemed to be missing and other mechanical assemblies were seized so the task now is to work out exactly what's included in the box of bits and if nothing vital is missing maybe begin refurbishing and reassembly.

Next ... ASSEMBLY of the receiver commencing with the fitting of the tuning condenser.

 

 

 

 

 

 

 

 

 As it appears possible to swap the components fixed to the tuning condenser assembly I left the originals in place after a quick check on their values. Above... various views with the one immediately above showing the tuning condenser assembly screwed to the main chassis.

Below shows the drive shaft in position. This was slightly awkward because the ball bearings for the left hand bearing were loose in a packet together with a larger ball bearing which locates in a socket made up from the end of the shaft and a centre screw with a locknut (picure below right).

In this example the shaft was an interference fit needing some pressure to align it with the end ball.

One important point is to wind the inner gear wheel on the tuning condenser a couple of teeth clockwise to activate the anti-backlash mechanism. If this isn't done some backlash will be felt. Fitting the balls in the left bearing needed patience and grease to keep them in place. Fitting the single end ball was also tricky. I used long nosed tweezers and the ball covered in grease to place it in the shaft aperture via the hole immediately above the adjuster. Once fitted the ball is kept in place by pressure against the end plate. Some force was needed to push the ball into the mating aperture in the adjusting screw (fully out). Finally the screw is turned to just eliminate end play.

 

 

 

 

 During the fitting of the geared assembly (above) I'd noticed that the centre gear of the three had a small peg sticking out and wondered what it was used for. I decided to check this before proceeding otherwise a lot of rework may be necessary. I've come across this potential trouble before. In particular in the case of getting my HP8640B working (click to see). In fact that little peg is the key to the R1475's designers solution to preventing damage when spinning the tuning too close to the tuning condensers limit. Fortunately I have my assembled R1475 for reference and, although not easy to see, should enable me to set the geared assembly to the correct position. If I hadn't noticed, the tuning range would have been limited because a small mechanical assembly triggered by the peg would have prevented the dial from reaching its limit.

So back to the fitting of that geared shaft. I must disengage the tuning condenser gears and set things up as best I can.

 

 

 This is the key part of the revolution counter mechanism that prevents mechanical damage. It's mounted on the chassis between the two rightmost gears and triggered by a tiny peg on the centre gear against a spring. The end of the arm (left) prevents the cylindrical dial from rotating further than its end markings. Goodness knows how the set was designed... there are so many strange levers. One looks as if it's been twisted and bent out of shape.

 

The pictures below show my attempt to permit adjustments of the gears so that the peg correctly engages to stop the dial.

 

 

 

 Looking at my assembled receiver the peg is in-line with the chassis edges so a long screwdriver is positioned to indicate the peg position in relation to the chassis. The red marks on the shaft indicate its correct position.

Above, the tuning condenser gear position at its end position, noting that the twin gears have been set for anti-backlash operation.

In my case the end shaft screw is loosened to allow the ball bearing race (once its securing screws have been removed) to be pushed upwards to disengage teeth (but only just enough to prevent the balls dropping out).

A final?? check revealed I may have aligned the gears for the wrong end of tuning so I may need to repeat the exercise! In fact neither fully min or fully max of the tuning condenser be achieved so I balanced the two.

Next... fitting the dial to check everything is aligned.

 

 Was this an accident or is it a factory instruction to "bend and twist" to fit?

Do I straighten it now or wait until I get to fitting it?

Anyway it turns out to be the part I need to do a trial fit mounting the drum dial.

The dial has a ball bearing race at each end with the two tuning knobs at one end and the wavechange at the other. This long twisted/bent lever connects the wavechange knob to the yaxley switch wafers. Looks like another high precision fit.
 

This is a view showing the mechanism at the other end of the lever.  That bend is supposed to be present. The rear metal plate is used to engage with end stops.

After 40 minutes of squeezing in my bench vise and twisting with pliers the bar was still slightly distorted but then fitted perfectly between the wavechange switch (above) and the operating knob (right) which fits at the left end of the tuning dial (the end of which fits into that bearing). The whole assembly needs to be very rigid and in my example (the assembled version) the whole thing is seized up.

 

 
 

 Here's the lever in position between the switch and the ident mechanism for the yaxley switch. It passes through a slot in the chassis and has to be threaded through this from bottom to top as the slot is too narrow for the small bush on the end of the lever. The thing works perfectly so the reason for the mangled lever isn't explained.

Next I need to add the dial although this will be a temporary fit as it's too fragile to leave in place whilst the rest of the parts are fitted. I've copied the picture of the dial below. From left to right are the scales for the four wavebands. Each has a spiral slot into which locates a pointer indicating the frequency to which the receiver is tuned. The applicable section is illuminated by a lamp under the drum.

The ranges are a follows:-

2.00 to 3.62 MHz

3.58-6.44 MHz

6.38 to 11.38 MHz

11.24 to 20.14 MHz

Dial markings look most peculiar but are better once the MHz numeric strip is in place. This links the double digits to the whole MHz figure.

Once finally fitted I'll need to signwrite missing numbers on the dial and on the MHz strip (which is blank.. having been painted??)

Once I'm happy with the tuning arrangements I'll add the harness carrying the module sockets.

 

 

 I was inspecting the end stop lever and its operating pin and noticed wear on the lever. This was because the pin was so badly worn it had produced a groove in the lever and itself ending up with a flat section. The flat section was now clearly wearing the lever more as the bearing surface was obviously shiny. I couldn't see how to replace the pin without lots of dismantling including taking apart the centre anti-backlash gears so considered fiting a bush.

The pin had a max diameter of 2.34mm and a length of 5mm (which was now 0.5mm too short due to lateral movement from wear in the lever mounting bush). I found an M4 screw having 5mm of uncut thread (diameter 3.56mm) and drilled this with a 1.86mm drill, then enlarging the hole to 2.41mm. This gave a clearance of 0.07mm, then cut off about 6.5mm of the resulting tube, filed the ends flat and superglued the bush over the worn pin. See opposite.

 

 

 

 I fitted the set of module sockets (above) This is quite a messy task (ideally three handed) because the sockets mate into chassis apertures plus a set of four brackets held in place by a line of bent metal strips (four long plus two short) carrying captive 6BA screws. Next I'll fit the two loose tagboards then various pieces of metalwork. The main task is fitting the nine modules and I found that the previous owner had detached the valve skirts so that each circuit can be removed from its can, so I'll first check the components to see if any should be swapped. At this point I noticed numbers had been marked on the modules which had all been cleaned, assemblies detached and all the decoupling condensers had one end unsoldered. I wonder if these had been fully tested or just checked with an ohmeter for leakage? I checked all the resistors and none was too distant from its correct value. Some seemed to have parallel components because they read low. Nearly all the tubular condensers were bad with some readings cycling (marked "unstable") from high leakage.

Below, a list of plug-in units and the tuning indicator followed by a listing showing marked and measured (in brackets) resistor and condenser values (where 100n = 0.1uF).

 

 MODULE

 LOCATION

VALVES (REAR TO FRONT)

 RELAY UNIT

ON TOP OF 1

 NONE

 UNIT A: AERIAL UNIT (145)

1

 NONE

 UNIT B: BAND PASS UNIT (146)

2

 V1 CV1053

 UNIT C: RF OSCILLATOR (171)

3

 V2 CV1932

 UNIT D: SIGNAL MIXER & GUARD MIXER (11)

4

 V3 CV1347 & V4 CV1347

 UNIT F: BAND PASS FILTER

IN FRONT OF 4

 NONE

 UNIT E: FIRST IF (37)

5

 V5 CV1053 & V6 CV216

 UNIT G: SECOND IF (38)

6

 V7 CV1053 & V8 CV587

 UNIT J: SIG DET & BFO (170)

7

 V9 CV587 & V10 CV1054

  UNIT K: AF AMP & AGC DELAY (45)

8

 V12 CV1932 & V11 CV587

 MAGIC EYE

 FRONT PANEL

 V13 CV1103

 UNIT A: AERIAL UNIT (145)

10K (12.4K), 100K(113K), 100K(114K), 100K(102K), 10K(10.4K)

10n(68n), 10n(unstable), 10n(unstable)

 

 

     

 

Left is the old "Post Office"style relay with its RAF code marked on the side (10F-2495). My uncle (born in 1916) was emplyed at Strowger Works for the whole of his working life from before the war, then a break in the Army, rejoining the factory when demobbed until retirement in 1981. His job was tensioning relay springs.. he always refused offers of promotion, preferring to have a completely worry-free life.

During my graduate apprenticeship in 1965 at Strowger Works, then Plessey, I popped over and spoke to him (whilst he was adjusting a relay). About 12,000 people worked in the factory.

Note the yaxley switch wavechange sections located in the various modules need to be aligned with the main ident mechanisms then a connecting rod inserted so that all turn together.

The main purpose of the relay is to disconnect the aerial from the receiver in the second (calibrate) setting of the mode switch. In that setting, test signals from the BFO crystal oscillator should match a set of dial markings where the frequency is indicated in a black disk. Associated with this feature is a front-panel fine tuning control that enables the operator to match the frequency to the dial. This allows very accurate frequency readings to be measured.

The fine tuning control also serves to accurately resolve SSB especially when tuning wear or failure of anti-backlash makes this virtually impossible with the main slow motion control.

  

 UNIT B: BAND PASS UNIT (146)

3.3K(4K), 3.3K(3.8K)

10n(72n), 100n(134n)

 

 

     

 

 UNIT C: RF OSCILLATOR (171)

1K(1.2K)

100n(199n), 10n(13n)

 

 

 

 

 

 

 UNIT D: SIGNAL MIXER & GUARD MIXER (11)

1.5K(1.9K), 3.3K(3.8K), 33K(32K). 330(375), 3.3K(3.7K), 10K(11.9K), 3.3K(3.5K)

56K(65K), 56K(67K), 120K(133K), 3.3K(3.3K), 10K(10.4K), 100K(110K)

100n(198n), 100n(unstable), 100n(66n), 10n(12n), 100n(unstable), 100n(151n)

 

 

     

 

 UNIT F: BAND PASS FILTER

No resistors/condensers

 

 UNIT E: FIRST IF (37)

3.3K(3.8K), 100K(10K), 3.3K(3.4k), 1M(1M), 1M(1.1M), 560K(622K)

10n((unstable), 10n(213n), 100n(170n), 10n(64n), 100n(unstable)

 

 

     

 

 UNIT G: SECOND IF (38)

3.3K(3.4K), 1M(1.2M), 560K(673K), 560K(665K), 56K(67k), 3.3K(3.6K),

68K(78K0, 1M(1.5M)

10n(12n), 100n(48n), 500n(113n), 100n(100n), 100n(55n)

 

 

     

 

 UNIT J: SIG DET & BFO (170)

560K( ), 1K(1.2K), 47K(53K), 10K(11.2K), 270K(320K), 2.2M(1.5M), 2.2M(1.5M)

1M(414K), 120K(148K)

10n(12n), 100n(282n), 100n(210n), 100n(137n)

 

 

     

 

 UNIT K: AF AMP & AGC DELAY (45)

22K(22K), 1M(1.3M), 270K(326K), 120K(140K), 330K(360K), 150(165), 560(630)

500n(800n), 20n(86n)

 

 

     

 I totted up the condenser requirement and arrived at the total in the modules to be 20 x 0.1uF, 8 x 0.01uF, 1 x 0.02uF and 2 x 0.5uF.

I decided to use 500 volt surface mount capacitors for the 0.01uF, 0.02uF, 0.1uF and the 0.5uF as I have around 700 of 100nF chips. For the 0.5uF I'm using 4 x 0.1uF in parallel.Opposite in a saucer are 21 x 0.1uF replacements fitted with wire ends. These tested at 122nF with a few slightly higher 124nF or lower 117nF. The new 0.5uF both tested as 498nF.

Below, the modules ready for their new stuffed capacitors.

The fact that all tubulars have been disconnected suggests drilling and stuffing to keep originality, With 31 of the things I made a simple jig to assist with the drilling. This used two blocks of wood as a clamp. I drilled a block of wood with a 17mm hole for a typical condenser and two holes for bolts then halved the block and used M8 bolts to hold it together. Using a pillar drill and a tool made from a sharpened tube, I cut around the wire-anchor solder pads then pressed them into the body. This worked fine on most condensers but some were difficult because the size of the pad was too large for the tube-tool. Pressure on the tool pressed the pad into the body but larger detached pads proved difficult to remove without help from a drill and tweezers in some cases.

 

 I eventually finished the new capacitors including one on a chassis-mounted tagboard. After unsuccessfully trying to seal the ends with a couple of things I chose candle wax with my soldering iron set to 200C which was the perfect solution as at that temperature the wax didn't burn. Now comes the long-winded task of refitting the stuffed condensers using the pictures I'd taken earlier as a guide. To simplify matters I'd used my SM 100nF chips throughout. Finally all the modules were reassembled ready for fitting.

Next I went through the remaining bits. I can't find the magic eye brackets or an output transformer (driven by a 6J5 with various outputs), neither are SK1 or SK2, the 4-pin Jones connectors present, and I've yet to see what valves are in the box. Nothing vital is missing in terms of the contents of my junk box.

Below is a simplified circuit of the receiver. Click for PDF version (which is enlargable).

Because of the design of the receiver the wiring is in two parts.. viz. the set of plug-in modules and then what can be termed "chassis wiring". The simplified circuit diagram below isn't at all useful for my task of rewiring. Instead I'll be using the chassis wiring diagram on the following webpage. This can also be selected as an enlargeable PDF.

Now to tackle the wiring

 Return to Reception