Grundig NF 1

[UncleBernie]

Hello, I have inherited a Grundig NF 1 that was still functional a few years ago, and I'd like to make some renovation on it. There are has two major issues (beside the usual replacement of caps and resistors) :

1 - the power transformer is made for 220 V main, and my main is rather 240 V.
I have seen in that post https://www.diyaudio.com/community/threads/photo-gallery.71300/post-6843380 the work that Pamook has made on the same amplifier. To lower the voltage from 230 V to 220 V he put a 12 V transformer in series with the main transformer. Can someone explains me the process and what kind of transformer I should use to get from 240 V to 220 V ?

2 - I know that it is recommended to replace the selenium rectifier with a silicium bridge, but some resistors have to be added as the voltage out of the silicium will be higher than the one from the selenium, if I'm not wrong. How may I calculate the needed resistors ?

Thanks a lot in advance.

 

[Magz]

Here is a link to a thread on another site wherein I describe my efforts to turn an NF1 into an iPod dock. It should answer many of your questions as you proceed.

https://audiokarma.org/forums/index...-console-amp-meets-i-pod.400078/#post-5287498

 

[UncleBernie]

Thank you, Magz, I'll have a look at that.

 

[analogadikt]

lower the voltage from 230 V to 220 V he put a 12 V transformer in series with the main transformer. Can someone explains me the process and what kind of transformer I should use to get from 240 V to 220 V ?

https://sound-au.com/articles/buck-xfmr.htm

Regards,

 

[UncleBernie]

Thank you, this will be very useful.