Rees Mace (Pye) 619 TX and CAT Receiver outfit
For a number of years I've been aware that, whilst having operational WW2 Army and Royal Air Force stations, the Royal Navy contribution has been sadly lacking. True, I've had a Murphy B40 for a while but, although a serious "boatanchor", it is just a receiver. Finally, with the help of the curator of the Royal Navy Museum at HMS Collingwood, I was now in a position to rectify this shortcoming.
The choice of equipment brought about something of a dilemma. The Navy tended to go in for rather large bits of kit! The main transmitters (such as the Type 89Q or 8M) were massive and, by definition, built like the proverbial battleship! So I was looking for a secondary transmitter/receiver setup - something that I could actually lift! The problem was that this role was largely filled during WW2 by the American TCS equipment. Superbly designed and engineered though this kit was, it just wasn't British (and it was the wrong colour)!
The answer was to jump forward slightly to the post-war period. During the 1950's, specifications went out for relatively compact equipments for secondary use on large vessels or to be fitted as the main communications gear on smaller ships. Two companies appeared to have been involved, Murphy and Pye/Rees Mace (Rees Mace became part of the Pye group). Both companies won contracts. The Murphy equipment was the 618 transmitter and CAS receiver and that from Pye/Rees Mace was designated the 619 transmitter and CAT receiver.
My problem was that I had the choice of both sets. I had waited what seemed like ages to acquire a naval setup and now two came along at once! As in the case of the B40, the Murphy equipment was very traditionally built - the word "clunky" springs to mind. The Pye/Rees Mace equivalent seemed a bit more innovative - and it was lighter (an important factor for a collection to be housed in a loft)! So I had pretty much decided on the latter. On viewing the hardware on offer though, I almost changed my mind. The Murphy equipment was in far better condition. The Pye/Rees Mace kit had seen better days - the 619 transmitter having rusting chrome and rather grubby panels. However, I stuck to my guns and brought back the equipment pictured above.
I envisaged that one of my first problems was going to be the lack of a mating connector for the transmitter. I had been warned by the Collingwood museum staff that they were like "hens teeth". All I had to go on was that it was an 18 way circular type, possibly made by Plessey. So that's what I typed into Google and I was pleasantly surprised to find that Roy at "Electrojumble" had new ones in stock (Plessey Mk7) at very reasonable prices. I was also extremely grateful to VMARS archivist, Colin Guy, for scanning a manual on the equipment into the archives at my request.
So, having taken the "before" pictures (never forget to do this!) it was time to start work. Being supremely confident that the kit could eventually be made to work (!) I decided to do the cosmetic work first. So it was out with the WD40, T-cut, Bakelite polish and lots of elbow grease. I started with the receiver and to convince myself I was winning, I did the job in two halves. This was the half-way point:
When I was happy with the appearance it was time to start working on the circuitry. In fact there wasn't that much to do to the receiver. I replaced a few of the paper capacitors, (particularly the one feeding the grid of the output valve) and gingerly applied power from a lashed up a power supply. Initially it worked on only a few of the ranges but following a few squirts of switch cleaner and vigorous operation of the band switch, the receiver was fully working. And the performance? Well, the sensitivity dropped off a bit on the higher frequencies but on the LF bands it was fine. Certainly OK for 3615kHz where it would be used almost exclusively. The "Wide" and "Intermediate" filter positions were pretty good for AM and SSB but the crystal filter on the "Narrow" position was only really suitable for CW.
The only real issue was a rather annoying spurious signal toward the top end of the 80 meter band (it was the second harmonic of the second oscillator). Now the manual indicated the presence of a series-tuned acceptor circuit to shunt this to ground. In reality, however, there appeared to be a parallel-tuned rejector circuit in the anode feedback. I wasn't convinced of the efficacy of this arrangement and removed it ready to re-configure it per the circuit. To my surprise, however, just removing the rejector completely eliminated the problem!
The "tarting up" of the 619 transmitter needed quite a bit more work. As can be seen from the "half-way point" picture above, the chrome on the handles was pretty grim. However, a combination of Brasso and steel wool achieved a reasonable result. Perhaps not as shiny as originally intended but a vast improvement on the as-received state. The captive bolts were a similar challenge. These were removed and put in the chuck of a power drill which speeded up the process considerably. Cleaning the bakelite knobs was particularly satisfying. At some point paper labels had been sellotaped onto some of them - removing these was great fun! The panels themselves came up beautifully revealing quite a smart looking set, in my opinion. Shame that the Rees Mace badge had been damaged - however, I suppose a replacement might turn up one day.
Producing a power supply for the transmitter was a bit more involved than for the receiver. It needed ~500V, 300V, 12.6VAC and bias and relay supplies of -50V. I set myself the challenge of getting all this from one rather chunky transformer that I had lying around. I remembered a rather elegant circuit that I'd seen for powering a MkII 19 set. By using a bridge rectifier in conjunction with a centre-tapped HT winding, it is possible to get 600V and 300V at the same time (let me know if you need the circuit). A heavy 6.3-0-6.3V winding looked as if it would just about be man enough to power the valve heaters. The only remaining problem was the provision of a -50V supply. Luckily there were various other heater windings available which could be series-connected to get about 18V. A voltage tripler circuit was then used to achieve the desired supply. Needless to say, the whole thing will eventually be safely enclosed in an earthed metal case. However, it's no good building a box until you know how big it needs to be!
Before applying any voltages, I thought I'd better have a look at some of the components. The problem was that the transmitter used lots of TCC "Metalmite" capacitors. These are notorious for going leaky (second only to the horrible Hunts "Mouldseal" types mentioned elsewhere on this site). I replaced those in the most risky circuit areas, such as modulator grid coupling and PA decoupling, with 1000V disc ceramics.
So it was time to start bringing the TX back to life. The heaters all lit up OK with the application of 12.6VAC - that's the easy bit, albeit very satisfying. Next, 300V was applied to the VFO and buffer and this was where the fun started. Smoke and actual flames told me that something was not quite right - it seems I hadn't replaced enough capacitors!
Now leakage in capacitors decoupling cathodes and even screen grids doesn't usually cause the magic smoke to be released. But those in HT supplies are a different story. HT decoupling resistors are often low enough in value to pass quite large currents before they expire - hence the fireworks (it's funny how it always takes a quite few seconds before the off switch can be found in these circumstances!). This persuaded me that all of these dodgy capacitors had to go. Some were pretty difficult to get at but I think I got them all in the end.
Having survived the smoke test the good news was that the VFO was now working. A nice fat carrier could be heard in a nearby receiver. Now it was time for the real excitement - application of the 500V (actually over 600V but who's counting!). Now the original PSU used to handle all the RX/TX switching, etc. Looking at it's circuit diagram it could be seen that this was quite a complex arrangement. The outputs of multiple transformer/rectifiers were obviously switched in sequence by a plethora of relays (this may have accounted for it weighing in at over 100lbs!). My lash-up arrangement was somewhat simpler. The 300V HT could be left on permanently. All that seemed to be required was to energise the carrier relay (turning on the VFO/buffer), switching the built-in aerial changeover relay, and applying the 500V supply to the PA and modulator. I opted to relay-switch the latter so that the whole setup would have one switch changeover. This relay was placed in series with the 500V choke with a snubber to limit contact arcing. Monitoring the various supply voltages and currents should be no problem due to the comprehensive metering arrangements - one of the features that had drawn me to the set.
NB - I recently realised that leaving the +300V on the TX without the +500V is NOT a good idea.The modulator screen grids pass rather a lot of current! I now leave the +500V on and relay switch the +300V.
So, fingers were crossed, wood was touched and, with the TX output connected to a dummy load, power was applied. Although drive was present and the PA drew anode current, it seemed that this couldn't be dipped and there appeared to be no output. What I hadn't fully appreciated was the complexity of the output tuning arrangements. Although basically a Pi tank circuit, the number of possible combinations of coils, coil tappings, fixed and variable capacitors was mind boggling. After much trial and error (mainly the latter) the correct settings were discovered for 3615kHz and I was rewarded with a suitably healthy dip, a good 40W of RF output and a nice blue glow from the miniature 807s!
Modulation was a bit more problematical. There was only one triode ahead of the phase splitter so the microphone input was not very sensitive. It looked like the transmitter had been designed for a carbon microphone - probably the Tannoy multi-element type which had a massive output. Also, the microphone transformer had been in the power supply which I didn't have! However, using an output transformer from a domestic receiver which had a tertiary winding for its tone control, I was able to get roughly the right impedance ratio to match a carbon type microphone biased with some current from the -50V supply. Modulation now looked good on a scope and on-air reports on the VMARS AM net were very encouraging.
So we were up and running (albeit with something of a temporary lash-up in the power supply department). All I need to do now is to find some suitable naval expressions for use on the air - I wonder what happened to those Navy Lark tapes?