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improved BIAS for old DR103 versions

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kentuckytukker:
Hi DR103 fans,

We all now that the original old Bias winding voltage of the power transformer was to less. (35VAC) to use to set a proper operatin bias voltage. I do have a Dutch clone which has only 32,5VAC winding for this purpose. So digging through the excelent info, gathered together by Mark Huss at hiwatt.org, I planned to upgrade the amp with his improved Bias schematic. As no actual physical layout was provided on Marks website I have designed my own. It still uses the 23 way turret strip to accomodate most additonal electronic parts. It is recommended to instal the Bias pot or pot's by drilling a hole(holes) in the top plate. This pending you integrate a common bias for a matched quad output tubes or use matched pairs. To my opinion we should go for a matched quad, as when doing a replacement we most of the time will replace all tubes at this stage. I'ts also recomended to add 1 Ohm bias measuring resistors at each output tube. This will eleminate the need for buying a special adapter. Pardon using English in this topic, but although I can read, speak and understand German language very well, it takes me to much time to write this down in proper German

kentuckytukker:
It is recommended to use the original layout of Mark as a reference too, because not all the wiring details at the 23 way turret strip is shown in my sketches.

kentuckytukker:

--- Zitat von: kentuckytukker am  1.12.2019 17:39 ---It is recommended to use the original layout of Mark as a reference too, because not all the wiring details at the 23 way turret strip are shown in my sketches.

--- Ende Zitat ---

kentuckytukker:

--- Zitat von: kentuckytukker am  1.12.2019 17:06 ---Hi DR103 fans,

We all now that the original old Bias winding voltage of the power transformer was to less. (35VAC) to use to set a proper operatin bias voltage. I do have a Dutch clone which has only 32,5VAC winding for this purpose. So digging through the excelent info, gathered together by Mark Huss at hiwatt.org, I planned to upgrade the amp with his improved Bias schematic. As no actual physical layout was provided on Marks website, I have designed some bymy own. It still uses the 23 way turret strip to accomodate most additonal electronic parts. It is recommended to instal the Bias pot or pot's by drilling a hole(holes) in the top plate. This pending you integrate a common bias for a matched quad output tubes or use matched pairs. To my opinion we should go for a matched quad, as when doing a replacement we most of the time will replace all tubes at this stage. I'ts also recomended to add 1 Ohm bias measuring resistors at each output tube. This will eleminate the need for buying a special adapter. You just measure the mV across these resistors and it will give you the actual bias current in mA. Allt htis without any additional calculation. Pardon for using English in this topic, but although I can read, speak and understand the German language very well, it takes me to much time to write this all  down in proper German language.

--- Ende Zitat ---

kentuckytukker:
Hi DR103 fans,

Unfortunatelly a small mistake has been discovered in both the layout circuits. :'( A jumper was missing between turret 6 and 13. I've updated the sketches now.
See rev.1 of the attached documents

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