1956 CEI Beta 6 transistor MW radio (Italy)

[howard]

Hello again,

I picked up this little Italian transistor radio off Ebay UK ages ago for under £10 including postage and it turned out to be the first transistor radio built in Italy in 1956 ! It looks very different from the contemporary British PAM 710, housed in a small leather case just 7 inches wide. Its chassis is unusual in construction with components suspended in space on a tinplate chassis which also provides multiple earth points, and it has no wax capacitors, most are polystyrene. Its typical six transistor complement as listed on RMOrg is OC44 or OC170 or OC171, OC45, OC45, OC71, OC72 and OC72 although this example has 2 x OC170 IF transistors and at least two French transistors fitted including an SFT320. Production of the radio continued into 1958 and it was also marketed as the Selonyx Cicala, Selonyx Tingal and the Hermann Titanphon. This example was complete and in fair cosmetic condition but it didn't work so I passed it over to Ron Bryan and he did all the repairs to the chassis and managed to get it working well again. There were no schematics available for the set so Ron sketched a circuit diagram by examining its component layout.

It wasn't easy working out how to remove the chassis from the case, the seized on volume control knob fell apart when levered off its spindle, and then a threaded collar under it screwed on to the pot thread was removed. The perspex dial secured by the threaded bezel was removed, the dial scale plate underneath lightly glued in place was carefuly levered out and then two csk screws underneath that were revealed and unscrewed and the chassis complete with loudspeaker then came out the back of the case.

The set was connected up to a 9 volt power supply and eventually the local radio station County Sound on 192 metres MW could just be heard. The screen wires on the two OC170 IF transistors were unsoldered from the chassis but no improvement was achieved. They were in fact in good condition, with no tin whisker shorts, so the screens were re-attached. The audio stages were checked and the voltages were ok. Tacking a 100uF cap across the driver transistor emitter cap increased the audio volume, the original 100uF electrolytic must have been internally corroded because a lead fell off when it was unsoldered.

The signal tracer showed that the second IF stage was not allowing signals through. A voltage check on the OC170 confirmed there was no collector voltage, proving that the second IFT primary was open circuit. A temporary Weyrad IFT was tacked in place of the original IFT to see if the set would then work and then strong signals were then received all along the MW band. The original IFT was removed from the chassis, dismantled and a repair attempted. The ferrite pot core assembly was removed from the screening can and the ferrite removed from the coil former by gently warming it up to soften the securing wax. One wire from the primary had 'green spot' as it entered the coil and was broken and just a 2mm bit remained. The ends of the 5 thou thick enamelled wire were carefully scraped and tinned with help from a little Fluxite. Not having any suitable enamelled wire a strand was taken from some 7/0.2mm tinned copper, a small loop formed at one end and tacked onto the stub of the broken wire, and the other end soldered to the coil pin. The break in the primary was successfully repaired and the IFT was reassembled and replaced on the chassis. The set then worked well and pulled in signals across the whole MW band. The alignment was checked for completeness, the IF was pretty close, but was given a slight tweak and the aerial trimmer was adjusted to peak the HF end of MW.

The set came back to me to be reassembled and cleaned up. The volume control knob was glued back together, the perspex dial cleaned and polished with Brasso, the case cleaned as best I could (there are bits of gloss paint remaining on the surface of the leather which unfortunately refuse to shift), the wires to the battery box replaced as the originals had been extended with tape wrapped around the joints and the set reassembled .

This little first generation transistor set works very well with excellent sensitivity and with good sound quality for its modest size, and my thanks to Ron for fixing it, a remarkable piece of work. Below is the circuit diagram drawn up by Ron in Visio from the sketches made during the repair.

Howard

[Sideband]

Excellent work once again Howard! That third picture gives the set a very 'home made' look about it



Rich.

[Andrew2]

What a great little set, and a nice bit of rescue work too. I'm surprised to see the OC170 was around as early as 1956 though.

[howard]

Originally Posted by Sideband

Excellent work once again Howard! That third picture gives the set a very 'home made' look about it. Rich.

Thanks Richard,

But I think Ron deserves all the credit for this repair ! Its construction certainly is unusual.

Originally Posted by Andrew2

What a great little set, and a nice bit of rescue work too. I'm surprised to see the OC170 was around as early as 1956 though.

The OC170 first appeared in the Philips Valvo catalogue in 1958 so this example may well be a later one. There's very little information available for this set but its production did apparently commence in 1956 probably with an OC44 transistor.

Howard

[Hybrid tellies]

A very unusual and interesting little set. Well done Howard and Ron another very worthwhile restoration.