In looking over many more photos of the US made 7s, I don't see any variation in wiring, only the 7K kit from Japan shows some variations. The 7K had the shielded wire connecting the cathode to toneamp instead of the yellow single conductor.
As far as the 7C designation, I started using the 7C designation after seeing most of the service manuals use it and it appears to be there only to designate whether you were ordering it with wooden case or not.
As far as the 7C designation, I started using the 7C designation after seeing most of the service manuals use it and it appears to be there only to designate whether you were ordering it with wooden case or not.
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HollowState, you mentioned you would leave your 7's out for a few days and to ask if anymore questions. I've got two more and I think I will have all I need. If you are not able to come up with answers by a quick look, please don't spend any extra time digging because you've been more than gracious already!
1. Is the ground path for the short ground buss at V1 going to chassis as photos seem to indicate via a short wire going to one of the turret board brackets?
2. Can you determine what the ground path is for the long ground buss? Looks to be tied to a terminal of C103 (middle PS cap can) but wondering if that terminal is tied to the can's case and if the case is isolated from chassis or not?
1. Is the ground path for the short ground buss at V1 going to chassis as photos seem to indicate via a short wire going to one of the turret board brackets?
2. Can you determine what the ground path is for the long ground buss? Looks to be tied to a terminal of C103 (middle PS cap can) but wondering if that terminal is tied to the can's case and if the case is isolated from chassis or not?
Yup, got the answers.
1) The short ground buss does in fact tie to chassis ground by a short bare wire soldered to a ground lug under a bolt that secures the turret board to the tube mounting frame. This mounting frame is affixed to the rear panel by three bolts. Each of these three bolts go through a fairly rigid rubber spacer to help absorb shock. But the metal is electrically connected by the bolt itself.
2) The long ground buss does connect to the middle can capacitor's negative terminal. The capacitor is isolated from ground by a phenolic mounting plate. The other end goes to ground by a slightly roundabout route. A short (4") length of shielded cable's shield connects the buss to the input selector switch. (Remember the missing 1 meg resistor thread?) That connection on the switch is unused. But there is a black wire from that point, through the laced cable array, that grounds at the input connector for phono 1 and tapehead. Since these two ground points are close to each other, it's almost a common or single point ground.
You can see the black wires below the 47K resistor on the input jack. And also the black wire on the rotary switch.
1) The short ground buss does in fact tie to chassis ground by a short bare wire soldered to a ground lug under a bolt that secures the turret board to the tube mounting frame. This mounting frame is affixed to the rear panel by three bolts. Each of these three bolts go through a fairly rigid rubber spacer to help absorb shock. But the metal is electrically connected by the bolt itself.
2) The long ground buss does connect to the middle can capacitor's negative terminal. The capacitor is isolated from ground by a phenolic mounting plate. The other end goes to ground by a slightly roundabout route. A short (4") length of shielded cable's shield connects the buss to the input selector switch. (Remember the missing 1 meg resistor thread?) That connection on the switch is unused. But there is a black wire from that point, through the laced cable array, that grounds at the input connector for phono 1 and tapehead. Since these two ground points are close to each other, it's almost a common or single point ground.
You can see the black wires below the 47K resistor on the input jack. And also the black wire on the rotary switch.
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My biggest concern was being able to replicate the path of the long buss to power supply ground so this gets me what I need. The other end of the board is convoluted how they pulled off the phono end with using the selector as a post etc but I guess it obviously worked for the Marantz team.
Thanks again for all the effort you made to get the photos and follow things out!
Thanks again for all the effort you made to get the photos and follow things out!