A modded Cossor 54

[Murphyv310]

Those spiders are eating up your EHT  

[Freya]

Your doughnut image could be showing a missing or exhausted area on the cathode, can remember doing the same on a Mazda CRM tube which looked like craters on the moon. Has to be said it still produces a great picture in daylight.

[Geordie McBoyne]

Frank's Cossor 54 motivated me to try out my set today.  First result was a spot in the centre of the screen. A partial short circuit across the HT supply was caused by the lid of one the IF stages screening boxes coming into contact with a component in the HT circuit. Lifted the lid and short circuit gone.
Now have a dim raster. The CRT isn't good.  There's a fault in the signals circuits somewhere. The RF circuits resemble those in the model 1210 and the post-war model 900.
The frame oscillator is a Cossor type 4TP, a valve that's just about impossible to find. Andrew Beer has made for this set a plug-in replacement which employs an ECL80. A miniature auto transformer in the B7 base provides the 6.3volt heaters for the ECL80. 

Geordie McBoyne.

[`FRANK.C]

HI Geordie McBoyne
Thanks for sharing those photos. The spot on you looks pretty bright in that photo.
Your set looks good and clean. I note it has a speaker cloth.
Am I right in thinking that these sets don't have a implosion screen? At this one I have doesn't and I cant see how one would fit.
It is good to know that there is a solution to the unobtainable 4TP.

Frank

[peter scott]

That's great to see you've got a spot on the CRT Frank. Perhaps Cossor thought that if the CRT in their 339 'scope didn't need a safety glass then why bother with it in the 54. Even half naked girls don't need safety.



Peter

[Murphyv310]

Of course health and safety wasn't even thought of back then Peter.

[Geordie McBoyne]

Acquired my Cossor 54 in 1993 when it was still possible to find and buy pre-war TVs for considerably less than the figures asked nowadays for similar sets.

There is no protection for the screen of the CRT.  A console version of the model 54 was made which had a larger CRT. The model 65 as the name implies the set has a 6" X 5" screen.

Close up of the plug-in replacement for the 4TP triode-pentode.  It is essential that the ECL80 is fully warmed up before the EHT rectifier.

Geordie McBoyne.

[Panrock]

Of course health and safety wasn't even thought of back then Peter.

Funny - that picture makes me think more of "Health & Efficiency"! 

What was the type of 6-inch tube in this set? Anyway, it looks a good 'un.

I attach the table including such tubes that appeared in Aug. '48 Wireless World. Strangely, the VCR97 (listed as such) is absent.

Steve

[Panrock]

As far as I can glean from Steve McVoy's site the SU2150(?) tube is not a plug-in replacement for the VCR97 etc., having a different 10-contact base. (Sliding contact bases for valves seemed to be all the rage generally in 1938-9 sets.)

[`FRANK.C]

Thanks for confirming that there was no Implosion screen.
It did look as there was no place to fit one. But I couldn't be sure I thought it may have been removed to make room for the magnifier.

That replacement for the 4TP is a very neat solution for a valve that cant be obtained.

Steve
Thanks for the CRT chart.
I don't actually know what tube is in it. The label that is on it is blank. Either it was never wrote on it or is totally faded.
I will soon remove the tube for safe keeping while I have a look at the rest of the set. When I get it out I may be able to see something useful on it.

Frank