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'Convertible' 405-line sets

 
ntscuser
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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

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Topic starter Posted : 03/11/2015 2:48 am
Nuvistor
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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

Frank

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Posted : 03/11/2015 10:31 am
Till Eulenspiegel
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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.

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Posted : 03/11/2015 3:37 pm
ntscuser
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Great pictures, thanks Till :aad

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

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Topic starter Posted : 03/11/2015 6:45 pm
Till Eulenspiegel
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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.

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Posted : 03/11/2015 7:45 pm
ntscuser
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I see, thanks Till

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.

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Topic starter Posted : 04/11/2015 2:46 am