1933 SBR Ondolinette 345U AC/DC 5 valve MW/LW compact superhet

[howard]

Hello again,

I won this little SBR Ondolinette radio at the Wootton Bassett auction a few months ago for £60 and all the other 1930s sets there towered over it as it's only 13 inches high. SBR, an abbreviation of Société Belge Radio-Electrique situated in Uccle, Brussels was the largest native radio manufacturer in Belgium and this was one of their first superhets with a complement of American valves, 6A7, 78, 77, 43 and 25Z5. There's a museum of SBR radios here ...

http://www.eeuwfeestpaleisje.be/big/inventaris.htm

It had obviously been restored in the past, its case had been professionally revarnished and inside it had had a step down transformer discretely fitted (it is a 110v/ 130v AC/DC set) and a few capacitors replaced but judging by the types used, that was probably 30 odd years ago. It was sold as working and indeed it did, not terribly well with instability at the high frequency ends of both MW and LW but considering its age and most of it still original that's pretty good going. There were one or two cosmetic issues outside, its original grille cloth was torn and it had a few light scratches but there was no damage or signs of woodworm and it was complete with all its original covers and bakelite trim and knobs. Inside its chassis was a bit dusty but entirely rust free. A nice period feature is that its dial is calibrated 1 to 100 and it has a lit cursor which moves around behind it. I managed to find its circuit diagram on the web.

I tested every capacitor in the set (the originals are rated in centimetres, 1cm = 1.11pf) to find that most of the replacements were already duff, and that the originals were still working, only a couple were leaky and all still had some capacitance. Ron Bryan checked the originals as well but sadly found them to be passed it. So I replaced all the replacements with new axials, and then stuffed new axials into the cases of the originals and plugged the ends with black Milliput. I also checked the resistors and found a pair of 250k ohm originals wired in series which tested at only 300k ohms so I replaced them with a new 500k resistor. The set still had a couple of its original Belgian Adzam brand valves (Mazda spelt back to front, made by MBLE, Manufacture Belge de Lampes Electriques) but replacement NOS valves for this set are as cheap as chips, the 6A7 and 78 looked scruffy and were coming apart so for just £2 apiece I acquired new ones. After all this work the radio was working much better and with a decent aerial it was picking up most stations on MW loud and clear. The instability on MW at around 1500 kHz had gone but it remained unstable at the high frequency end of LW. I checked the frequency at which the LW instability started and it was at around 400 kHz which is outside of the LW band.

So I took the set back over to Ron for realignment. The IF frequency was checked first, on this set it should be 370kHz but it had been set at 400kHz so that was corrected. This set has only one adjustment for LW at the lower frequency end of the band and the trimmer was already at its limit so in an attempt to set the lower frequency correctly, capacitors were tacked across the trimmer and eventually by trial and error a 330pf capacitor did the trick. That had no effect on the instability at the high frequency end of LW of course, and there's no adjustment for that end so the tuning capacitor tunes way off the LW band eventually reaching its IF frequency. The entire LW band is tuneable though and with a decent aerial it now works well picking up Radio 4 loud and clear and RTE and French stations come over well too. MW needed a minor adjustment at the high frequency end of the band and tunes perfectly.

I polished almost all the scratches off the case with Safecut car polish. There was nothing I could do with the loudspeaker grille cloth, it had disintegrated so I looked everywhere for 1930s upholstery material of the same or similar pattern but without luck. Eventually I bought a small piece of gold antique loudspeaker material off Ebay for under £5 and fitted that over the original and it looks very nice. If this ever became a very valuable radio then I would have a new piece woven to the original pattern.

This little SBR superhet radio works well and much like a modern radio, yet it's 77 years old. It's a pretty little art deco style set in superb condition and very compact for a table radio of its time. My thanks to Ron for his help getting this lovely little radio working well again.

Howard

[JoshWard]

Aww, it looks a pretty little thing

Well done

[Sideband]

Another superb job Howard. I bet there are not many of those around...not in the UK anyway.


SB

[howard]

Originally Posted by JoshWard

Aww, it looks a pretty little thing
Well done

Thanks Josh, it takes up about a quarter of the space that each of the other 1930s sets I've got here take up.

Originally Posted by Sideband

Another superb job Howard. I bet there are not many of those around...not in the UK anyway.
SB

I doubt if there are any others in the UK, I know of three in Belgian collections, one in the SBR museum mentionned above and another one in a German collection. I suspect that this one was brought over from Belgium at least 30 years ago when it was already 40+ years old and then restored here - it had replacement UK capacitors in it including a Hunts mouldseal so it was some time ago. It was done well though.

Howard

[Herald1360]

Interesting circuit- looks like no AGC, an aerial attenuator / IF gain control for volume control and is that an anode bend detector?

Couldn't make head or tail of the right hand half of the rectifier circuit until I finally thought energised field loudspeaker

[chipp1968]

I remember that set.Very nice .Worth having that one.

[Patrick Dixon]

That looks like fun - and a lovely job as always.

I like the capacitance in cm!

[Radio_Dave]

That's a very nice radio. Well done Howard

David

[howard]

Originally Posted by Herald1360

Interesting circuit- looks like no AGC, an aerial attenuator / IF gain control for volume control and is that an anode bend detector?
Couldn't make head or tail of the right hand half of the rectifier circuit until I finally thought energised field loudspeaker

Yes. You're right.

The lack of AGC is a slight problem as I live next to a MW transmitter, County Sound on 192m MW. At minimum volume it's still playing quite loud.

A closeup pic of the chassis taken from the front and a pic of the capacitor stuffing WIP.

Howard

[julie_m]

Lovely looking set, although the circuit is a bit weird! Is the step-down transformer an isolating type or an autotransformer? I'd be very wary of a chassis that could become live.

Interesting that they used large numbers of centimetres when expressing capacitance, as opposed to just using larger units (I spotted a 1km. capacitor in there) ..... reminds me of something I saw in the Beano once (back when comics were drawn properly.....) where a bunch of characters lined up for the start of a race, and a small sign could just be seen: FINISH LINE 150,000cm. THIS WAY.

[Tim]

Lovely looking set Howard. Well done.

Lovely looking set, although the circuit is a bit weird! Is the step-down transformer an isolating type or an autotransformer? I'd be very wary of a chassis that could become live.

I thought it was an AC/DC design.
Series heaters and the symbols near the mains input are perhaps indicative of this, but it is a foreign set after all.
I thought the inductors on the mains side were DC smoothing coils and perhaps speaker field or heater hum buckers. I'll have another look!

[Herald1360]

The step down TX is a later addition- it's visible in one of the rear cabinet views. It's not in the (original) circuit.

[howard]

Originally Posted by Herald1360

The step down TX is a later addition- it's visible in one of the rear cabinet views. It's not in the (original) circuit.

That's right. These AC/DC sets were originally 110v when fitted with a barretter, or 130v without. I suspect for 220v operation a line cord dropper was used. After it was shipped over here a transformer was added to drop the mains voltage from 240v to 110v or 130v.

Howard

[Tim]

Ahhhh, I see it now.Fair dinkum.