12-03-2017, 12:45 PM
hi everyone!
its been a while, but im nearly done replacing the caps and resistors in my philco 118. ive been saving this one section for last, because it wasnt making any sense to me, and also because it had obviously been fiddled with at some point in its life.
the caps we are looking at are the big electrolytic caps, #73 and 74 on the schematic....73 is the 8mfd and 74 is a 8 and 10 mfd multisection. in my actual chassis, it looks like something happened to the 8mfd section of #74, so they put in a 20mfd replacement cap.
the part thats got me confused right now is it looks to me like theyve got ground running to the positive pole of the 10mfd cap in #74. correct me if im wrong, but the case of the can caps are ground, right? because theres definitely a ground lead from a nearby bakelite block (#34 if i remember correctly) going to the center pole of the 10mfd section of the can cap, not to its case. so is the 10mfd in the circuit backward? that is to say, positive to ground, and negative goes out to the rest of everything?
this is probably basic stuff for you guys, but im still learning the basics, so please bear with me. ive seen this before, where your electrolytic goes in backward with respect to ground because youre dealing with negative voltages, but its not clear to me if that is the case here.
ive included a picture of the schematic in the area im talking about, as well as a photo of my actual chassis. in that photo i have already clipped out the big replacement 20mfd they had stuffed in there, but you can clearly see the ground lead from the bakelite block on the left running to the silver lead in the cap on the right, which is 74.
any help you guys can give would mean the world, i really appreciate everyones help as i fumble through the learning curve.
Brian Foose
its been a while, but im nearly done replacing the caps and resistors in my philco 118. ive been saving this one section for last, because it wasnt making any sense to me, and also because it had obviously been fiddled with at some point in its life.
the caps we are looking at are the big electrolytic caps, #73 and 74 on the schematic....73 is the 8mfd and 74 is a 8 and 10 mfd multisection. in my actual chassis, it looks like something happened to the 8mfd section of #74, so they put in a 20mfd replacement cap.
the part thats got me confused right now is it looks to me like theyve got ground running to the positive pole of the 10mfd cap in #74. correct me if im wrong, but the case of the can caps are ground, right? because theres definitely a ground lead from a nearby bakelite block (#34 if i remember correctly) going to the center pole of the 10mfd section of the can cap, not to its case. so is the 10mfd in the circuit backward? that is to say, positive to ground, and negative goes out to the rest of everything?
this is probably basic stuff for you guys, but im still learning the basics, so please bear with me. ive seen this before, where your electrolytic goes in backward with respect to ground because youre dealing with negative voltages, but its not clear to me if that is the case here.
ive included a picture of the schematic in the area im talking about, as well as a photo of my actual chassis. in that photo i have already clipped out the big replacement 20mfd they had stuffed in there, but you can clearly see the ground lead from the bakelite block on the left running to the silver lead in the cap on the right, which is 74.
any help you guys can give would mean the world, i really appreciate everyones help as i fumble through the learning curve.
Brian Foose
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