R1355 GEE Receiver


 Above is a 1949 Clydesdale ad for the R1355 with RF units. These were sold for conversion into Band I TV receivers, often with the Type 62A display unit shown below. I recently rejected an offer to sell me a pair of these equipments for £695, but I did buy an example of the R1355 receiver not too long ago for a lot less. To my surprise it had been completely rewired and fitted with brand new components. Clearly someone had spent a lot of effort but for what end result? See the pictures below. The blue/yellow example is mine whilst the plain one is just a basic unpainted modified example.

Note the orientation of the upper (unwired) 6-way connectors. The front panel was also painted in yellow before being roughly painted in blue.... all part of its history.






 Above, the transformer has been renewed and the choke removed, but both examples shown here appear to have been modified for a similar purpose. Note the unwired upper connector. That white cable is the mains lead, and two blanking covers are fitted over holes drilled for an earlier modification. The blue receiver is fitted with a lower 4-pin plug for its mains supply, some examples like the example below fitted with an RF26 had a 6-pin plug which is missing one of its VR65 valves.. now maybe a 6V6 for driving a loudspeaker carrying TV sound?


 Below... note that pot fitted to the PSU chassis isn't wired.



 Above.. note the new components.


Above.. 5 stages of amplification at 7.5MHz followed by an AM envelope detector whose output is filtered and passed to 2 stages of AC amplification. Click the circuit to see an alternative version.

All is slowly being revealed... I managed to unplug the RF24 with some difficulty because the thick blue paint was jamming the metalwork. Much to my surprise, although the three valveholders were wired up and various wires extended towards the upper side of the chssis, the coils, behive trimmers and valve caps were unwired. All three valves are new SP61's and checking those in the main receiver revealed, not VR65's but again, brand new SP61's. The valveholders look new as do the front panel connectors and Pye plugs. The restorer never did finish the job. I should probably do this but after getting rid of that blue paint.... done! The front panel doesn't come off because its welded to the chassis. First coat of matt black.










 G019445 is the serial number of the blue RF24.whose chassis is yellow just like that of the R1355.

It certainly looks like original yellow paint, but could the previous owner have stripped both equipments down to basic metalwork and had them sprayed? I reckon nearly all the components are new. That includes the valves their holders, plus all the resistors and capacitors (even tagstrips which are all labelled with their RAF numbers). For some reason the project was never completed. If you examine the second picture above you may notice the beehive trimmers are not wired up and the coils have just unsoldered wire ends poking out. The switch isn't wired up either (in fact it's never been wired up), neither are the valve top cap leads. If you examine the tuned circuits in the schematic above you may also note several damping resistors and fixed capacitors are not fitted. Whoever was responsible for the work didn't complete the job.

Oddly the blue paint was wet when the RF24 was fitted because its case had well and truly stuck in place, leaving the outer case behind when extracted from the R1355.


The label cleaned up nicely rubbing fine emery paper on the lettering.

Click the plate on the top right to see an untouched example of an RF24B

Those securing screws were a right pain as finding correct size screws was virtually impossible so I ended up drilling the plate for slightly larger self-tapping screws and after drilling the front panel I fitted the alternatives. The last owner didn't have decent screws either so he used the original rusty ones.




The RF24 front panel came off easily and where the yellow paint has flaked off is revealed clean bare metal with no sign of any original black coating. Removing the panel entailed loosening of the front of the ceramic switch carrying the ident mechanics and the long operating lever. Because the switch wasn't wired the front section just dropped out.

An odd modification was found that must have been made during reassembly viz. the bakelite knob, secured by a set screw, was drilled for a split pin as if a loose knob was a stock fault in the RF24/RF25. In fact, checking other examples I found all had a cotter pin securing the knob and one of these RF units had an extremely stiff switch. Ideally I should fit a proper pin as the split pin makes operation incomfrtable.



 Another puzzle is the pair of Pye plugs. The one on the RF24 was very loose and failed to tighten up. I discovered the mating threads were different sizes allowing only a couple of turns before seizing up. As the material is brass I was able to secure the front carrying the thread into a vise and turn the other part using a 16mm spanner creating a matching thread allowing the two halves to be tightened. Both were stamped on the front "943-9142". Either the parts are faulty or someone mixed up the two mating parts.

A suggestion which I believe answers the puzzle is those numbers are part of a "modern" NATO stock code for a metric-threaded connector whilst early WW2 examples used a British thread. Parts from the two types must have got mixed up.


A big improvement over the blue version.. The switch needs some channel lettering and the turnscrews need refitting once their fresh paint has dried. The handle now stripped of blue and yellow paint was fairly rusty (now rubbed down to remove the worst) which probably suggests the condition of the original RF24 was much the same before painting yellow.

 Just waiting for the blanking plugs. Oops.. I put the two multi-way connectors on upside down just like they were fitted in the blue panel...

I suspect the rotary switch below the connectors should be fitted with a grub screw not a 4BA bolt and that split pin on the RF24 knob is horrible.

 To proceed further is quite daunting. Although both the R1355 and the RF24 appear substantially complete the wiring between tagstrips and major components other than valveholders was never completed. The majority of work is around the two rotary switches. I could use an old RF unit, which would mean finishing off the receiver, if I decide to see if the whole thing works. To do this I'd need to reverse engineer the circuit diagram and investigate the yaxley switch to determine how to tackle the anti-jamming wiring. I imagine the power supply is OK. The mains lead extends to the front of the R1355 where it's been cut, but has it ever been tested and fired up? I didn't notice the EA50 diode rectifier but hopefully it's lurking under the chassis and what's under the IF cans... are the coils and other components present? It goes without saying that the original high-cycle power unit has been stripped out and a 50Hz one fitted. Does this mean the R1355 was once converted for TV used and hence RF/AF wiring/component changes made for this purpose or did the "restorer" revert to the original R1355 design? Clearly lots of detective work is required....

 Below.. a schematic of the original hi-cycle power supply for aircraft use. A previous owner of the R1355 has removed many of the components and fitted a 50Hz mains transformer to supply AC LT of 6.3 volts and a DC HT supply, keeping V5 the voltage regulator, and deriving the negative bias supply from the HT supply rather than the EHT supply which is no longer fitted. To re-constitute the negative bias rail is tricky as the original circuit was part of the EHT system and as such was very variable in voltage with respect to loading. Advisory figures are quoted of -150 volts with R41 (75Kohm) load and -230 volts with R41 switched out [see the wiring details for this condition]. To understand the new power supply in respect of the bias voltage I'll need to check its wiring and carry out some tests. The circuit digram will be supplied later...

A quick check revealed no bias supply but the Partridge mains transformer has loads of terminals and may include a winding suitable for a bias supply, or an elevated voltage range suitable for deriving a bias voltage from the HT negative feed.


 Below is the content of the last, larger screening can (opposite V7 and V8) in which you can see the elusive V6, a VR92 or EA50 rectifier. I opened each of the 6 cans and all had been refurbished with new resistors and capacitors.




 To segregate from the main descriptive material the wiring details are here...

R1355 Wiring


Read about GEE


Return to Reception