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Old 30th August 2011, 05:56 PM   #11
DF96 is offline DF96  England
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EZ81 limits are 100mA DC at 450V AC (160mA at 250V), 50uF reservoir cap, and series resistance of at least 310 ohms (150ohms at 250V). You can exceed one of these provided you keep well below the limits on the others.

100uF breaks one limit, so are you on the safe side of the others?

BTW your diagram is wrong. EZ81 has separate connections for heater and cathode.
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Old 30th August 2011, 07:55 PM   #12
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If the EZ81's filament is powered by a 6.3 volt winding that is otherwise grounded for the needs of other tubes it is powering, and if the EZ81 has a heater cathode short within it, you will definitely have glowing plates!

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Old 30th August 2011, 08:42 PM   #13
DF96 is offline DF96  England
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Good point!
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Old 31st August 2011, 02:33 AM   #14
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My friend will order a new tube. We will start from there.

Thanks for all your help and comments.
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Old 2nd September 2011, 02:21 PM   #15
jim is offline jim  Belgium
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You could try to temporarily replace the EZ81 with 2 1N4007 diodes and check if the B+ is correct then.
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Old 7th September 2011, 04:38 AM   #16
lechuck is offline lechuck  Netherlands
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You stated that the EZ81 glows red when you turn it on and you have no B+ voltage. I have had the same thing one time with a 5AR4, it turned out that the filter capacitor had shorted out which caused a short circuit.

Based on my previous experience I strongly recommend you to check the power supply for any short circuits
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Old 7th September 2011, 07:24 AM   #17
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My friend first of all disconnect the amplifier from the power supply and try once more. Then if you still have the same I would suspect the 1st servoir capacitor which i would suggest to change it with a 47uf MAXIMUM. In case the problem is the EZ81 tube just try to replace it with two silicon diodes just for checking. In case you try this disconnect the rest of the circuit because the HV will be a bit higher than before.

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Old 13th November 2012, 06:52 PM   #18
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Originally Posted by kevinkr View Post
I suspect you should replace the EZ81 before going any further.. I would also add 1M/1W flame proof metal oxide resistors and 0.01uF/1kV ceramic caps across each 1N4007..
Old thread I know, but the search function on this site is amazing. I'm in the process of building an amp using a 6BY5 rectifier with an Antek toroid PT that has no center tap for the filament winding. Thanks very much for the tip.

Last edited by scott17; 13th November 2012 at 06:56 PM.
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Old 15th November 2012, 03:15 AM   #19
TheGimp is offline TheGimp  United States
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I hate to hijack a thread, but I don't want to start one just for this question.

Can anyone identify this full wave rectifier?

It has the same pin out as a 6X5 or 6ZY5, but the plates seem a bit large compared to the 6X5s I have. One can see all the way through the tube between the plates. There are "T" shaped heat fins that are about 1" across the top of the T and 1/4" perpendicular to it.

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Old 15th November 2012, 09:05 PM   #20
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Could it be a 6AX5GT?

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