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In Reply to: Re: HP branded Amperex 6DJ8/ ECC88 tubes - Help! posted by kentaja@yahoo.com on September 22, 2004 at 07:19:28:
Is there a site with pix of open vs. closed plate and/or getter format? We have lots of old HP and Tek scopes here. ;-)
Follow Ups:
I too have a collection of old Tek scopes for parts.I'll post some pictures soon and then everybody can take their time identifying them and listing the various frame, plate, and getter strictures etc.
I have never seen a site with pics of the various plate types.The names I give for the plate structure is of my own choosing. It seemed logical to me. Later production Philips 6DJ8 had the 'open' plate structure. The plate halves do not mate and a small bit of metal is spot welded on the plate halves in the area between the top and bottom mica spacers. You can clearly see the grid and heater. I think Philips started using this plate type in the late 60s. I have never seen one of these with an earlier production date.
With 'closed' plate, earlier production, the plate halves mate so you cannot see the internals of the tube and the connection between the plate halves is made above the top mica spacer. While I have a few examples of this type of Philips tube from the early 70s, generally later production Philips/Holland no longer used this plate structure. Perhaps these were produced much earlier and date coded later once sold to HP. Just a guess on my part.
All of the Japanese produced tubes I have from the 60s and 70s produced on Philips tooling use the closed plate. I also note the new JJ produced tube use the closed plate. To my ears, the closed versions are generally better.
mt
Thanks everyone for the very useful insight'.
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