Quad 405-1 Woes - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

sennsai · 3rd Jul 2022, 12:16 pm

I found the Snook 2.5 mods a little too ambitious for me so completed the boards with Bernd Ludwig's basic mods.

On test, the boards seem ok however when I fitted D13 and the 10ohm resistor to TR9 base, the bias changes.

prior to fitting D13, bias volts on Tr9= 0.57, Tr10= 0.4.

after fitting D13/10ohm, volts on Tr9=0.16 Tr10=4.7.

So, I'm not sure which one is best. In all instances, DC volts on outputs were around 1Mv or less.

3rd Jul 2022, 12:16 pm	#21
sennsai Tetrode Join Date: Jun 2016 Location: Worksop UK. Posts: 77	Re: Quad 405-1 Woes I found the Snook 2.5 mods a little too ambitious for me so completed the boards with Bernd Ludwig's basic mods. On test, the boards seem ok however when I fitted D13 and the 10ohm resistor to TR9 base, the bias changes. prior to fitting D13, bias volts on Tr9= 0.57, Tr10= 0.4. after fitting D13/10ohm, volts on Tr9=0.16 Tr10=4.7. So, I'm not sure which one is best. In all instances, DC volts on outputs were around 1Mv or less.