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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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It is currently 21 Apr 2018, 08:42

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PostPosted: 11 Apr 2018, 18:01 
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Joined: 13 Jan 2018, 21:33
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Woodo wrote:
quite possibly the dropping R value should be worked based on 2A as there are two windings. not sure how the transformer ratings work. if so that would mean a 4 watt 1R.

edit: Reading further about this it looks i should be using 1.2 A. Also the V drop of the bridge rectifier is 0.9v per diode giving 1.8v drop. So dropping resistor needs to drop 8.4 - 1.8 - 5 = 1.6v at 1.2 A. if correct that is about 1.9 w 1.3 R. Alternatively the approach used in the 300b set in Gio’s link above is to use a further adjustable regulator.


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PostPosted: 14 Apr 2018, 07:28 
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edit: updated schematic from another look at the pcb


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PostPosted: 16 Apr 2018, 21:47 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
You can use resistors to drop the voltage. However, you will likely end up doing trial and error to get the right value. The issue with using resistors is the heat generated. In that regard, you will want to use resistors with power ratings much larger than the power to be dissipated. Give consideration to spacing and airflow around the resistors. Most heat issues won't arise until after several hours of continuous operation, so keep that in mind when testing.

Also note that with 6V transformers you may be cutting it close even with a low dropout regulator like the LT1085.

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PostPosted: 18 Apr 2018, 22:12 
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Thanks Gio. I expect it will be a lot of trial and error mixed with the experiences of those who have had success on the site.


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