Need to construct a better chassis for this Riviera Radio receiver, the present circuit resembles the battery version of the KB Pup.
I've tested the tuned circuit and it's hopeless, there's something not right with the coil. I don't expect to tuning to be all that sharp but this one hasn't any selectivity whatsoever. Like the Pup two triodes are employed. It's the usual arrangement, leaky grid detector with reaction which is transformer coupled to the output valve. The transformer has open circuit windings.
The problem here in the North-East is that three stations are grouped very close together and simple TRF radios have difficulty separating them. The Philips "Superinductance" sets can though
Till Eulenspiegel.
Tuning coil resistances are 2.5 ohms for the medium waveband and 51 ohms for the long waveband, the latter seems to be too high.
Using a signal generator the medium waveband coverage is proven to be 600 to 1300Khz. Medium waves is marked as "SW" on this made in 1930 set.
Switch to LW, set the signal generator to 200Khz. No resonance at that frequency, instead the 'scope is showing a modulated waveform irrespective of the position of the tuning capacitor.
Till Eulenspiegel.
That's curious looking set!
Is that its own cabinet? Or a repurposed one from something else?
Any clues to the quite large discrepancy over the coil resistance?
Hi Marion, the Riviera Radio was made by the British Radiophone Company which in due course evolved into the well known Plessey company. Like certain KB radios the Riviera was acquired by saving up cigarette coupons.
I bought the set simply for it's looks knowing the innards are just simply junk. so the choice is restore the existing electronics or build in something better?
From Grace's guide: https://www.gracesguide.co.uk/Plessey_Co
Till Eulenspiegel.
Yeah! That's a lot to read at bedtime!
Now then, surely, the fun is to get the junk working properly again? - I remember being cock-a-hoop at getting a few crackles out of a crystal lash-up, let alone to be able to listen to an entire programme on it!
I reckon, let's first see what it can be made to perform like in its original guise, and only then consider new 'guts' for it if it can't be revived?
But I'm trying find an excuse to use this valve:
http://www.tubebooks.org/tubedata/hb-3/receiving_tubes_part_1/1D8-GT.PDF
Diode, triode and output pentode all in one bottle.
Hi Frank, indeed, the time has come has come to make use of the 1D8GT valve and it's application can be in the Riviera Radio receiver. The tuning coils have been sorted out and are giving full coverage on both wavebands so I can implement Marion's suggestion of retaining much of the original design. The circuit diagram shows a leaky grid detector which requires reaction to sharpen up the tuning. The detector introduces damping on the preceding tuned circuit and a bit of positive feedback will improve the Q of the circuit. An anode bend detector is out of the question for this type of receiver and in fact I don't know of any battery radio receiver that has ever used such a detector.
Did Philips make battery Superinductance radios?
Till Eulenspiegel.
@till
I know little, nothing, about the Superinductance radios.
An anode bend detector is perhaps not the best with the way modern MW stations compress the audio to the max and probably increase the modulation aswell.
Not tried it but I think that type of detection would not handle that signal well.
Frank
Hi Frank, the Philips "Superinductance" radios are truly impressive performers, even the earliest models such the 834A have good selectivity, maybe not as good as a superhet receiver but nevertheless not that far behind.
https://www.radiomuseum.co.uk/834a.html
Later models like the 472A do perform as well as any superhet. Even have AVC.
Getting back to the Riviera Radio, the audio coupling transformer has open circuit windings and will need rewinding.
Till Eulenspiegel.
Hi David,
How's the project going? - Did you get the transformer rewound?
Hi Marion,
Ed Dinning has rewound the interstage transformer for me and it's ready for collection. The transformer has a 2:1 step-up ratio. The original tuning coil will be retained so the only hope of achieving any selectivity will be by means of the positive feedback from the reaction coil to raise the Q of the tuned circuit. The circuit as it stands now employs two triode valves. Mullard PM2HL detector and PM2 output.
Till Eulenspiegel.
Does that still let you graft in your ID8GT?
Not being funny here, but is it my dyslexia, or does that valve ident look like "IDEOT" (idiot) to anyone else?
Just thinking on this radio, surely, it must be about as minimalist as you can get, isn't it?
hi Marion, I see it as 1D8-GT, but I have not heard of it before this thread.
Frank
I'm having second thoughts about using the 1D8GT in this receiver, much better to keep the circuit as close to the original as possible and employ 2volt valves. The diode-triode-pentode valve will be better employed in a superhet receiver which is it's intended application. I don't know of any European equivalent to the 1D8, if there was such a thing it would have the Pro-Electron code of DACL30, or something like that.
Till Eulenspiegel.
I must say that the 1D8GT reminds of the EABC80 (triple diode, triode), in as much as the number of individual 'valves' that have been squeezed into one small glass envelope.
Testing the Riviera Radio.
Refitted the rewound transformer and a Mullard PM1HL into the detector valve socket. The modified Ekco AC12 power supply provides the 2volts for the filaments and 47volts for the PM1HL anode. Connected the 'scope to the secondary of the coupling transformer. Ten feet of wire for the aerial. Now comes the big surprise the set actually works and with careful adjustment of the reaction control more than one volt of audio is available across the transformer secondary. Selectivity is not too bad and the reaction control sharpens up the tuning. Next, fit another triode valve into the output valve socket, wire up an output transformer and loudspeaker. Supply the output valve with 120volts and 1.5volts bias, the triode I'm using is a Mazda HL2, not really suitable as an output valve. I'm now getting results from the loudspeaker, not very loud but it does prove the set works. A pentode would be much better for service as the output valve but the socket only allows a four pin valve to be used. The earliest version of the Mullard PM22 has a four pin base and a side terminal for the screen grid, this valve would be ideal but the chances of finding one are slim. The answer is an adaptor base which will allow a wide choice of pentode output valves. The Mullard PM22A or it's equivalents. The octal base KL35 and the Mazda Octal PEN25 can also be considered.
Till Eulenspiegel.
I must say that the 1D8GT reminds of the EABC80 (triple diode, triode), in as much as the number of individual 'valves' that have been squeezed into one small glass envelope.
Hi Marion,
I'll take a picture of the internals of this unusual valve.
Till Eulenspiegel.
The 1D8GT
The triode output valve has been replaced with a pentode. The new valve is a Cossor 220HPT = PM22A. This has necessitated the fitment of a five pine valve holder.
The result is a real improvement of audio output. A separate grid bias battery is required, the PM22A needs 4.5volts when operating from a 120 volt HT supply. The output transformer and loudspeaker will be taken from a scrap Pye P114BQ.
Till Eulenspiegel.
