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Audio Research D70 mark1 + schematic

Hallo ! I´m trying to repair a D70 from 1983 . It has a 6DJ8
which determine the "workingpoint" for itself and the following two 6FQ7 tubes for each channel . This poweramp has no solid state parts and the cathodes of the 6DJ8 have two 1,5k resistors connected to each cathode ...... not 110 ohm and 511 ohm as mark 2 . I would very much like to find a schematic for this version of the D70 . ( The two 6FQ7 tube
in each channel have just two 6K powerresistors from their cathodes to earth ...... no other resistors as in version mark2 ) Regards Stewen
stewen1
pmotz
375 posts
 
Take a look at the Audio Research Corp. Database (ARCDB) at http://www.arcdb.ws Look under Amplifiers, then D-70. At the bottom of the D-70 page are a couple of schematics. Can't be sure which model, Mk I or Mk II, but the date is 1982/1983. They are hand drawn so I don't know the source and I doubt ARCDB knows either. They just post pictures people provide. Very doubtful you will get anything out of Audio Research, so good luck!
daveyf's avatar
daveyf
1,174 posts
 
Stewen1, I believe IF your D70 uses the 6FQ7's then it is a mk 2 version.
You could check with ARC themselves, they are VERY helpful when it comes to the amp and still service it. I don't believe Pmotz is correct in his assessment of ARC service.
stewen1 OP
9 posts
 
Thanks for answers ! Well , the schematic at www.arcdb is
an early mark 2 vesion with R13,R14 511 ohm and R12,R15 110 ohm . "My version has 1,5K for these resistors and its very
sensitive when I´m trying to set the +90V with the trimpot.
Can´t read the value of the trimpots ( four total) but when I measure it might be around 20K . The mark 2 version has 5K trimpots and I think it is much easier to set the "workingpoint" for mark2 amps. Do You think I should try a
modification here ? As I have found there are at least three
or probably more versions of the D70 model.
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