A modded Cossor 54

[Murphyv310]

Hi.
I'd think that the signal from a Hedghog or Aurora would be great enough without the preamp. Personally I'd remove it. Understandably it's part of the sets history but it is very much hidden from view.

[`FRANK.C]

Hi Adam and Trevor
It is a bit of a dilemma to know what to do with the extra amplifier. If it wasn't there so long it would be an easier choice. But it does look to have been there for a large part of its life.
The same goes for the cabinet. I would think that it has been altered for the larger part of its working life. Do I leave as is and try and find a magnifier like the one fitted or restore back to original.
At least I don't have to make those decisions for a long time yet.

Frank

[Freya]

I think the cabinet should be returned to as good as it can be as your going to be looking at it, especially removing the added accessory magnifier holes. But that's just my opinion.
The extra valve amp would not serve any purpose and in fact could be detrimental with our signal source being so strong.
Out of interest, was the set bought from its original location, was it in a remote location from the transmitter ?

[Mike Watterson]

I'd go for leaving the amp and restoring the cabinet with the magnifier holes, as both those may be relatively contemporary to the original sale. But just my opinion. Those both might have been common. The amp might even have been a rare factory mod?

An suitable attenuator can be used. It's not like the set is going to be used instead of a current model.

[`FRANK.C]

Hi Stephen
I have no idea of its original location. It would be good to know.

Hi Mike
It may have been a factory mod. But to me the way the valve holder is mounted looks a little crude for an official mod.
It is soldered to the nearby choke. The same way as the other choke was was mounted by being soldering to the speaker.

Frank

[Freya]

Just the speaker cloth left for you to do Frank  [attachment=21094]

[`FRANK.C]

Now you are setting the bar high Stephen.

[`FRANK.C]

I spent a little time on the TV today. I had another look at the choke that was mounted on the speaker. I has initially thought it was wired in parallel with the choke mounted on the underside of the chassis.
But on closer examination of the wiring that is not the case. I guess the fact that it was mounted on the speaker should have been a clue. The TV would have been originally have been fitted with energised speaker and at some point it failed and was replaced with a permanent magnet type. The choke was us ed to take the place of the energising coil.
Some of the wiring around the choke area is not matching the circuit diagram. How it is at present I cant see it being correct so it will need to be changed back.
The diagram I am working from can be found here. I note that at least some of the information there was provided by out own Geordie McBoyne. A big thank you goes to Geordie McBoyne as it is proving most useful.

It would be nice to refit a energised speaker. I had a search and found one potential candidate of the correct size. I have no idea what it is out of as it was given to me but most lightly a radio of some sort. The cone is a little tore but is salvageable. The speaker coil has continuity. As does the energising coil but I may need to rewind it to suit the higher current of the TV HT.

Frank

[Freya]

Certainly looks man enough for the job, may as well see if it holds up to the current as is. The rewind is pretty basic if it does fail.

[`FRANK.C]

Hi Stephen
I don't think it will work as it is. If nothing else I believe that the voltage drop would be too high.
The resistance of the choke I took out is 500R wheres the resistance of the energising coil is 2k5.
The inductance of the energising coil is 40H and the choke is 20H. Both those values will be less when there is DC in the coils.
The choke is most likely different to the original energising coil.
There is not much unused room left for a larger winding.

Frank