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PL36 or a PL504 ?

 
PYE625
(@pye625)
Famed V-Ratter Registered

The "Cavitrap" anode as used in the PL504 seems to have made it into a PL36 bottle.... at least it would appear so. The PL36 on the left in the first picture below is a standard earlier type. The one on the right is a later PL36. In the last photo, it can be compared to a PL504 and to me, the internals look identical. So, I wonder if it was easier for the makers' to simply produce the later PL36 using the more advanced innards of the PL504 ?

IMG 5075 50
IMG 5074 50
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Topic starter Posted : 03/08/2019 11:05 am
Nuvistor
(@nuvistor)
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You could well be right Andrew, by the end of the 60’s although valve production was in full swing I am sure they new they didn’t have much time left before valves became a replacement market. Economies would have been a priority.

Someone may have earned a bonus for putting the idea in a suggestion box, be nice to think so.

 

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Posted : 03/08/2019 6:17 pm
Till Eulenspiegel
(@till)
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From the Radiomuseum. The cavitrap construction technique of the PL500 can clearly be seen in the illustrations. https://www.radiomuseum.org//tubes/tube_pl500.html

Although described as a pentode the PL36 is actually a beam tetrode.  The was some discussion about the PL36 valve here: In post No 24  https://www.vintage-radio.net/forum/showthread.php?t=101350&page=2

Towards the end of UK production of the PL36 Mazda made the valve with the electrode assembly of the PL504.

Later on the Mazda PL36 was imported from the old German Democratic Republic.  

Till Eulenspiegel.

 

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Posted : 03/08/2019 8:49 pm
PYE625 liked
Till Eulenspiegel
(@till)
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In fact the Mazda PL36 in the Stella ST1007 was one of the late production made in UK valves having the PL504 cavitrap electrodes.  For some reason it didn't work all that well in the set and subsequently it was replaced with a Mullard PL36.

The problem was a peculiar squegging effect in the line oscillations.   The ST1007 employs the type of line timebase in which the flyback pulse is fed back to the grid of the triode discharge valve.  

Till Eulenspiegel.

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Posted : 14/08/2019 8:50 pm