Sterling band III converter MkII?

[Tractorfan]

Hi,

While sorting some stuff t'other day I rediscovered a Sterling converter that I've had for years complete with its box and instructions. I used to strip these down in my youth for the parts to make other projects. Now that they're getting rare, I've kept this one as is and had a look inside for old time's sake. However, I've just noticed that it's got an ECC85 valve within. I feel sure that the old ones I used to fillet used a PCC84? Does anyone know if this was the case and this one is a later (or earlier) version with a different valve, or are my lonely little grey cells up to their old tricks again?

The date code on the smoothing cap (JFQ 255) shows that it dates from February 1955, if I've read it right. HT is 165volts and no sign of bulging or leaking of the cap.

I don't suppose it's of any use in these UHF digital days, so just a curio then.

Cheers,
Pete

[HamishBoxer]

Hi Pete, I also have similar but as yet not opened it up.

Certainly need preserving.

[Peter.N.]

Brilliant they were, used to radiate ITA all over the neighborhood, the locals would get Ch9 free - at the same time as BBC. Although to be fair there were some that were a lot worse.

Peter

[mark pirate]

I have a couple of these somewhere, nice to have on show with single channel sets, but not a lot of use now.

I suppose they were the first 'set top box', doubling the amount of channels!

Mark

[turretslug]

I'd much rather figure out the circuit for this than for a Freeview box, the active device ratio must be about a billion to one! I think the PSU caps might last longer in this one, too...

[Synchrodyne]

A single ECC85 is suggestive of a circuit not unlike those often used for FM front ends, with say a grounded grid RF amplifier followed by a self-oscillating triode mixer. On the face of it not unreasonable as a simple way for Band III to Band I conversion with oscillator low, but local oscillator radiation could have been a problem, maybe more so than at Band II frequencies. It happened that Band III (174 to 216 MHz for the UK 405-line TV channels) was about twice the frequency of the full Band II, 87.5 to 108 MHz. Presumably the ECC85 was still good at 200 MHz, even though said to be optimized for 100 MHz. The earlier ECC81 was said to be usable up to 300 MHz.

I am not sure if a PCC84 could be used in the same role. The original cascode triode valve, the 6BQ7, was designed so that either triode could be used in grounded grid or grounded cathode mode. But it had an independent shield connection, whereas in the PCC84 the shield is connected to the second triode grid. Maybe the second triode as the RF stage and the first triode as mixer would have worked?

The attached Wireless World advertisement from 1959 shows an evidently more elaborate Band III converter, self-powered, with ECC84, presumably as a cascode RF amplifier, and ECF80, presumably as frequency changer.

Cheers,

[Heatercathodeshort]

Originally Posted by Peter.N.

Brilliant they were, used to radiate ITA all over the neighborhood, the locals would get Ch9 free - at the same time as BBC. Although to be fair there were some that were a lot worse. Peter

Ha! Ha! Peter. As a kid I had one of these by my bed side table connected to a PYE B18T. The original remote control. It worked incredibly well but unfortunately produced an unwanted Band 3 picture on neighbouring receivers!
As a 12 year old I was blamed for every crackle and pop of interference by my neighbours back then. Even with every possible measure taken to screen everything it could still hold it's own against Crystal Palace and produced patterns on my parents Ferguson 236T.. You'll wonder where the yellow went when you brush your teeth with PEPSODENT.. A wasted childhood. Cheers, John.
PS. That is very well constructed Pete.

[Peter.N.]

Been there, done that, got the 'T' shirt.

Peter

[Tractorfan]

Hi,
Yep! I did that too. I extended the co-ax and mains leads from the telly to the armchair and absolutely amazed our elderly neighbour when she came round for a cup of tea and saw me changing the channel from a distance! At least she wasn't seeing the interference on her own telly nextdoor!
I knew nothing about radiation of RF, and nobody ever complained so I remained in blissful ignorance.
Happy days.
Cheers, Pete

[Heatercathodeshort]

The problem with the B18T was it's unscreened, rather long twin balanced aerial lead that coupled the socket to the first R.F. stage. It must have acted like a perfect radiator.
They can still be fun. Connected to a TRF receiver with a Band 3 signal applied to the converter input, you can replicate the early days of Band 3. You won't get the patterning unless you leave the Band 1 Aurora connected and you and it's unlikely you will get Mrs Higginbottom complaining to your mum! Amazing nostalgia. John.

[Studio263]

I think Chas Miller was a fan of the Sterling converter, he mentioned it at length in on of his early Vintage TV features in "Television". Can anyone remember which issue though?

If it is still operable I'd be inclined to use it, set the modulator deliberately to a band 3 channel and downconvert to 41.5 MHz. You could always get two Auroras and two Freeview HD receivers to re-create BBC(1) and ITV on their original VHF frequencies (downside: £££!)

[Alf]

That converter brings back memories, as an eleven year old kid, I remember we had, I think, an Ultra V815 tv, band 1 only. Fed up of watching just the BBC tv, I remember swapping an old bicycle for one of those. In later years, I found that little mains transformer very useful for various projects.

[Tractorfan]

Hi,
Which rather neatly brings us back to my original question; Did some of these use a PCC84 instead of the ECC85 that mine has?
I too used the transformers from the ones I had in my past, but I seem to remember that the LT was 7volts and not 6.3volts.
Cheers, Pete