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It is currently 14 Aug 2018, 22:26

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PostPosted: 08 Aug 2018, 22:02 
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Joined: 08 Aug 2009, 03:11
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Location: Chilliwack, BC
Try a different tube?

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 09 Aug 2018, 01:40 
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Joined: 25 May 2016, 16:30
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Tried that! No difference


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PostPosted: 09 Aug 2018, 04:25 
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Joined: 25 May 2016, 16:30
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M. Gregg wrote:
Juancho wrote:
Hi, by input sockets connected correctly I mean they are correctly insulated and connected to the star earth point. The heater circuit is not grounded in this design so simply floating


Is this the schematic?
http://www.4tubes.com/SCHEMATICS/BY-BRA ... 0-89-4.gif
http://www.4tubes.com/SCHEMATICS/BY-BRA ... 0-89-3.gif
http://www.4tubes.com/SCHEMATICS/BY-BRA ... 0-89-2.gif

I don't see the heaters floating?
If this isn't the circuit do you have a link?

Regards
M. Gregg

I will certainly check the heater grounding for V1 2 and 3. This has been modified by someone and I'm pretty sure the earth connection has been removed
David


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PostPosted: 09 Aug 2018, 10:14 
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Juancho wrote:
I will certainly check the heater grounding for V1 2 and 3. This has been modified by someone and I'm pretty sure the earth connection has been removed
David


The reason I mention trying floating the heaters with a capacitor is possible cathode>>>heater leakage.
The capacitor will charge up to a potential and needs to be 600v low leakage.
The capacitor charges up and lowers the difference in potential between the two.
This is a common fault liked to oscillation via a grounding potential that varies with pot settings.
There are other things you can try on the grounding but its a good idea to check this first.
It could be the "mods" on the heater grounding are because its on DC but this isolation won't help the potential will vary and modulate the other heater voltages. NB not the heater supply but the potential from heater to ground.

Regards
M. Gregg

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