Schematic question

[calman46]

Happy New Phoenix Audio .
I have a Sony STR 6065 that I recapped for a friend . There are two common connection paths on schematic , one goes to chassis through the phono ground jack . The other path which includes the negative speaker terminals and negative center channel out jack goes to the protection circuit . I can't see on schematic were it connects to chassis but I'm get continuity from neg. terminals mentioned to chassis . There is no resistance it measures like a dead short. A noisy volume control that cleaning won't fix lead me to find this . The volume control is quiet now but I really didn't fix anything so the noise may return . If someone could take a look at the schematic and these two ground paths , it would be greatly appreciated. The volume pot was noisy before the recap and all the jacks are isolated from rear panel . thanks

 

[BlueCrab]

Spent a few minutes looking at the schematic. I see what you're saying - no direct connection from the negative speaker terminals to ground. Sorry I can't be of more help.

 

[Gepetto]

Everything in the schematic keyed with the BOLD black line is ground (even though they are not shown as connected on the page). Originates from the center tap of the transformer shown on the lower right of the schematic.

 

[calman46]

Bear with me please I'm self taught, The speaker NEG and the center channel NEG Bold black line crosses over the Center tapped of the transformer Bold black line ,but there is no dot showing a connection there(shown on same page). Also all the I/O jacks and speaker terminals are isolated from the rear panel . The phono ground jack(isolated from rear panel ) connects to the chassis which connects everything else to chassis . So why isolate the I/O jacks etc.. from the rear panel if there connected to it through the phono ground ? So is the schematic is wrong ?

 

[Gepetto]

There are other pages to this schematic which may disclose some important keys...

Generally speaking, you bring the circuit ground to the chassis at one and only one point. You want the chassis to serve as a shield but you do not want any currents flowing through the chassis, this can lead to ground loops.

 

[calman46]

The other schematic is of the tuner section which shows the FM IF board ground going to E but I can't find the other end of E on either schematic. When you get a chance take a look at the speaker protection circuit and that "ground" path . Would that work without a chassis connection ? Like it is drawn? Thanks

 

[VSAT88]

Try it

 

[Gepetto]

The other schematic is of the tuner section which shows the FM IF board ground going to E but I can't find the other end of E on either schematic. When you get a chance take a look at the speaker protection circuit and that "ground" path . Would that work without a chassis connection ? Like it is drawn? Thanks

Without the proper schematic or unit in hand, I have no way of telling if it will work without a chassis connection, or even if the ground run shown on the schematic page you have posted is tied to the chassis. Not enough context.

 

[calman46]

I'm thinking the schematic should have the connection dot where the two grounds cross. The tuner schematic is part of the SM PDF so I can't post it . The protection circuit is part of the amp board and the grounds on that board go to chassis . It plays great was able to set the bias and DC offset , which is real low .Its not mine so I'm not going to mess with it . That's for all the input .