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Old 21st April 2017, 04:54 PM   #1
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Default Mod 805 based amp without anode cap

My amp uses 805 tubes without anode caps. I cant find any data sheet for 805 without anode cap. But if i read this sheet correctly i only need to take the connection to the pin left of bayonet pin and attach that on the anode cap?

But this sheet makes me confused. The picture on the first page where the pins are numbered and the picture on the secound page dont match...
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Old 21st April 2017, 05:13 PM   #2
TheGimp is offline TheGimp  United States
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One is a bottom view, the other is a top view.

Yes, you need the anode caps for the 805 per the drawings or you have no connection to the anode (Plate).

Are you sure your amp is running 805s?

Pictures of your amp?

Schematic?
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Old 21st April 2017, 05:34 PM   #3
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You are maybe right. I think it is 805a tubes not 805.

Its these tubes i think: http://www.grantfidelity.com/images/RZ/805A-T.jpg

And I whant to use these tubes: http://grantfidelity.com/site/files/805T-spec.jpg

This is my tube: https://www.dropbox.com/s/g2oca9dqsu...20.12.jpg?dl=0
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Old 22nd April 2017, 10:09 PM   #4
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It appears that the "805a" is a "Modern Botique" version of the old RCA 805.
Just something companies do to capture a share of the market (partly because it is
more convenient too).
That is a little like when years ago Svetlana made "811" tubes that took the plate cap off the top, and connected the plate to one of the 4 pins below (811-3, 811-10, etc.).

I bet that the plate on your "805" tubes are connected to pin 3.

You will have to pull apart the amp, and see if the 805 filament power is connected to pins 2 and 4; and if the output transformer primary is connected to pin 3, and the driver tube (probably from a cathode, or from an interstage transformer secondary) is connected to the 805a grid pin 1.
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