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'20w pp. Sparks in tube.'
Author:brotor norway (registered user: 29 posts )
Date: Tue, Mar 20th, 2012 @ 04:37 ( . )

On 03/19/2012 @ 15:51, joe kerr wrote :
Hi Brotor and welcome to AX84. I think with the language barrier some readers are confused a little (me) I couldn't work out if you had cathode biased power tubes or fixed bias (negative voltage across control grids) So it seems you've built the core twenty watt amp with fixed bias? I'd suggest measuring all the voltages across each power tube pins and writing them down e.g. pin1 200VDC etc If you have sparks in tubes I'd take the measurements without the tubes in. Can you post a link to the OT specs data sheet? You can copy and paste a http address straight into the thread. You can also post links to photos from hosting sites like photobucket etc Just make the photos well lit and large so people can see details. As for the test point resistors you do need 1 ohm between the cathode and ground and check that you can measure that resistance with your meter when it's powered off.

Hi. You're right. Fixed bias. Pot adjusting negative votlage on grids. Plate voltage: 376VDC, GRID: -34V. EACH TUBE DRAWS 24,5mA.Sparking stopped when cross-changing the two wires going from the primary of the OT to the plates. But now, no sound. OT is: [link]

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--* 20w pp. Sparks in tube.
3/23/2012 @ 15:52--joe kerr

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