Peto Scott Trophy 8

[raditechman]

I have been given a Trophy 8 receiver and also the matching pre-selector unit.
Cosmetically both are in good condition.
The tuning drive cords are broken in the Trophy 8 and although I have downloaded the data for the receiver from this forums service data download service it does not show drive cord arrangement. Any clues from other owners?

Also the output stage in the Trophy 8 uses a choke/capacitor arrangement to feed headphones or a high impedance loudspeaker, see photo, I have seen in the Trophy 6 that they use instead a normal output transformer.
I would like to fit a normal speaker output transformer into the Trophy 8 but still keeping the original components in the radio for historic purposes. Any comments on that proposal?

John

[Tomshep]

Yes, but they are heretical. Keeping old components for the sake of originality is bunkum to me. It does little to increase the value of the set. The few hundred people worldwide with an interest in old radio sets are nearly all electronics savvy and know that judicious updating and modification improves performance and saves many an old knacker and I would sooner have one that works well
Assuming the output valve passes enough current to do so, I think that your best option is to measure the voltage drop across the choke at, say 1000 Hz and find a transformer of similar impedance.Expect to have to put a cap or two around it to tidy up the frequency response.

[PJC58-Hythe]

The valve should be a 6F6 or KT63 both have an optimum load impedance of 7000 ohms operating in class A so you just need to source a suitable transformer.

[Herald1360]

If you want to keep as much originality as possible, simply parallel feed the output transformer from the choke capacitor output. If you're using an external speaker, mount the TX in with that and just connect its primary as if it were the high impedance speaker.

[raditechman]

I will fit a sutable output transformer, the person who gave me the radio was a bit concerned when I said I would relace the choke system with transformer and that is why I shall keep the old (disconnected) parts in the radio.
I doubt if there are many of these radios about.
Lots of wax/paper capcitors to check!

John

[HamishBoxer]

Many about? Possibly not, I always fancied an 8 but I do have a Trophy 6. Perhaps I should just be grateful!

[G6Tanuki]

Parallel feed would be my path-of-least-modification too. Maybe increase the value of the capacitor between the choke and the headphone socket...

One of the little RS Universal valve output transformers would likely be OK for matching to a low impedance speaker, they have loads of tappings and so you can play around with the ratio to get the best compromise between power and quality. It's not HiFi after all..

[roadster541]

I have a Trophy 8 so can sketch the drive cord route for you. I am away from home with work at the moment but will let you know when I am home. You are very fortunate to have the matching pre-selector; I have never seen one. I found my Trophy 8 at the last Wooton Bassett and had been looking for one for some time. It is complete but not working and is next on my "to do" list. I am finishing off a Labgear LG300 transmitter at the moment and it would be nice to have, at least, started on the Peto Scott before the next WB in around six weeks time.
I have a very nice RME 69 which is an American receiver similar to the Trophy 8 and was very lucky to find the matching pre-selector in a WB auction!
I would also suggest mounting a suitable op xfmr in a speaker cabinet and connecting to the existing speaker/phone socket. I will use one of my period speakers with adjustable high impedance inputs; these are easily found at WB or similar events.
Good luck with it.
Rod
M0LXY

[roadster541]

Oops, I must have been tired when I posted last night; I had done a long shift. Peto Scott tuning drives used a flat rubber belt. I bought a cheap selection of cassette player belts to work out the sizes which I needed on my Wireless World 1938 communication receiver, which uses Peto Scott tuning drives. I will check the size when I get home, see if the trophy 8 is the same length and I may have a couple of spares.
Rod

[roadster541]

I am now home; do you still need the info. on the drive belts?

[raditechman]

Roadster541 Thank you for the offer of the drive cord threading diagram it would be most useful and appreciated. Or maybe a photo.

I am a bit puzzled by the rubber belts you mention, I do have plenty of cassette belts if needed but in my Trophy 8 which seems to use two drive cords one is missing and the other is broken and lying loose, the broken one is drive cord and not rubber belt.
Is a rubber belt needed for the missing one I wonder?

John

[roadster541]

John,
Here are two photos of the tuning drive on my Trophy 8. There are only two pulleys, both flat belt, one on the tuning knob spindle and the other on the reduction drive behind the tuning dial; the belt simply goes round the two pulleys . The present drive belt is a piece of knicker elastic about 3mm wide; it was already fitted when I got the receiver and does work surprisingly well.
I am confused by your mention of two drive cords in your Trophy8. Is the preselector built into the same cabinet?
Rod