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Forum 2

'Convertible' 405-line sets

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ntscuser
(@ntscuser)
Prominent Member
Topic starter
 

Further to the recent discussion about the Philips Twinline 'convertible' 405/625-line receiver in the suppliers section (no longer available) I found this snippet in the article "Converting the Convertibles" in the February 1964 edition of Practical Television:

The rest of the article can be found here: http://www.americanradiohistory.com/Arc ... 964-02.pdf

 
Posted : 03/11/2015 1:48 am
Nuvistor
(@nuvistor)
Illustrious Member
 

The sentence about the contacts lining up when the 625 strip is screwed down gave me thoughts of intermittent faults in its future use.

Frank

 
Posted : 03/11/2015 9:31 am
Till Eulenspiegel
(@till)
Illustrious Member
 

Pictures of the Philips "Twin Line" 625 line conversion kit. It was easy to fit and was reliable too. Could do with a bit more IF amplifier gain though.

Till Eulenspiegel.

 
Posted : 03/11/2015 2:37 pm
ntscuser
(@ntscuser)
Prominent Member
Topic starter
 

Great pictures, thanks Till :aad

I wonder if substituting frame-grid valves would have cured the low-gain problem?

 
Posted : 03/11/2015 5:45 pm
Till Eulenspiegel
(@till)
Illustrious Member
 

Great pictures, thanks Till :aad

I wonder if substituting frame-grid valves would have cured the low-gain problem?

The IF amplifier valves are EF183 and EF184. A three stage amplifier would have been better. The Thorn add on 625 unit was the same, just two frame grid valves. A transistor IF pre amplifier was available from the service department, this little unit really improved matters.

Till Eulenspiegel.

 
Posted : 03/11/2015 6:45 pm
ntscuser
(@ntscuser)
Prominent Member
Topic starter
 

I see, thanks Till Forum 6

I suspect low gain is less of a problem since the end of analogue transmissions.

Hopefully the buyer of that set is reading this thread.

 
Posted : 04/11/2015 1:46 am