Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on July 26, 2010, 10:25:49 am

Title: Which is the purpose of that germanium diode ??
Post by: kagliostro on July 26, 2010, 10:25:49 am

A friend of an italian forum is interested to change the final tubes of a Binson Amp

the question is about a version of the first stage

in that schematic there is a AO81 germanium diode (connected to 3.15v)

which is the purpose for that diode ?

http://www.audiofaidate.org/forum/download/file.php?id=1168&mode=view
http://www.audiofaidate.org/forum/download/file.php?id=1174&mode=view
http://www.audiofaidate.org/forum/download/file.php?id=1169&mode=view
http://www.audiofaidate.org/forum/download/file.php?id=1170&mode=view

Many thanks

Kagliostro

Title: Re: Which is the purpose of that germanium diode ??
Post by: DummyLoad on July 26, 2010, 12:06:39 pm

can you post the images... viewing of the files via the links is not possible unless you are a member.

Title: Re: Which is the purpose of that germanium diode ??
Post by: HotBluePlates on July 26, 2010, 12:26:24 pm

It looks like a small adjustable bias supply.

After the 200k pot and on the far side of the 2.2M resistor, the schematic shows -2v. I'd guess that the -2v leads to the grid of a preamp tube.

Title: Re: Which is the purpose of that germanium diode ??
Post by: kagliostro on July 28, 2010, 02:58:53 am

Here are the files

http://www.mediafire.com/imgbnc.php/1c62a2f905d4b4d77329962fac5559476g.jpg

http://www.mediafire.com/imgbnc.php/688795731ae566679e0c78f45db3300f6g.jpg

http://www.mediafire.com/imgbnc.php/4f91384196fe1d35edd98a5062a010456g.jpg

http://www.mediafire.com/imgbnc.php/7e25ba4e33fef6b29e452a59a7ef4e116g.jpg

http://www.mediafire.com/imgbnc.php/ee285f5021fb331489ed02f90f8e67896g.jpg

Sorry to post it only now

Kagliostro