bfglp
Member
- Joined
- Jul 30, 2009
- Messages
- 133
- Reaction score
- 5
Amp powered but was weak and trebly. It has new tubes all test as new and a new cream back speaker that sounds great with my Boogie.
Tried to bias it and v8a was OL and v7a 42mv plate voltage is was 474 and 475.5
Found a test recommended by Mad Scientist and ohms between pin 4&5 stoped 515 v8 & 517 v7
Following circuit from bias point I see that r67 has lost a good portion of its coating the bias pots respond to adjustment smoothly
So I believe that I found the issue is r67 but can only speculate the cause was someone frequently using the 1/2 power switch without putting the amp on standby first
Tried to bias it and v8a was OL and v7a 42mv plate voltage is was 474 and 475.5
Found a test recommended by Mad Scientist and ohms between pin 4&5 stoped 515 v8 & 517 v7
Following circuit from bias point I see that r67 has lost a good portion of its coating the bias pots respond to adjustment smoothly
So I believe that I found the issue is r67 but can only speculate the cause was someone frequently using the 1/2 power switch without putting the amp on standby first
