06-18-2018, 01:00 AM
I'm currently working on a Model 86 and it's got a few oddities that I'm curious about.
Question #1 - what with the 27 tube and it's placement slightly below the chassis?
[Image: https://farm2.staticflickr.com/1766/4286...9604_c.jpg]
Question #2 - probably a pretty basic question but why is no shielding necessary / used?
Question #3 - what does the right-most control do? The schematic labels 'range control' but it seems to be a combination of a small variable capacitor and a switch.
[Image: https://farm2.staticflickr.com/1749/4196...439d_c.jpg]
Question #4 - Why is there a switch for the power transformer primary winding (labeled 'primary tap switch' on the schematic)? What voltages does this set support? It's got a cover over it on the chassis so seems not normally supposed to be messed with by an end user. You can barely see it just below the filter bank near the mid-right of this picture:
[Image: https://farm2.staticflickr.com/1763/2899...ee48_c.jpg]
Question #5 - how critical is the grid leak resistor value? I believe it's supposed to 2M based on the labeled schematic but I measure 3.75M. The set seems to work fine and actually is pretty sensitive.
[Image: https://farm2.staticflickr.com/1724/2800...471e_c.jpg]
For reference, that's #20 on the schematic (Part #3083). In case anyone is interested, here is a PDF scan that includes the parts list (but not nicely labeled with parts values like Ron's version):
https://drive.google.com/file/d/1JkRvp2C...sp=sharing
Question #1 - what with the 27 tube and it's placement slightly below the chassis?
[Image: https://farm2.staticflickr.com/1766/4286...9604_c.jpg]
Question #2 - probably a pretty basic question but why is no shielding necessary / used?
Question #3 - what does the right-most control do? The schematic labels 'range control' but it seems to be a combination of a small variable capacitor and a switch.
[Image: https://farm2.staticflickr.com/1749/4196...439d_c.jpg]
Question #4 - Why is there a switch for the power transformer primary winding (labeled 'primary tap switch' on the schematic)? What voltages does this set support? It's got a cover over it on the chassis so seems not normally supposed to be messed with by an end user. You can barely see it just below the filter bank near the mid-right of this picture:
[Image: https://farm2.staticflickr.com/1763/2899...ee48_c.jpg]
Question #5 - how critical is the grid leak resistor value? I believe it's supposed to 2M based on the labeled schematic but I measure 3.75M. The set seems to work fine and actually is pretty sensitive.
[Image: https://farm2.staticflickr.com/1724/2800...471e_c.jpg]
For reference, that's #20 on the schematic (Part #3083). In case anyone is interested, here is a PDF scan that includes the parts list (but not nicely labeled with parts values like Ron's version):
https://drive.google.com/file/d/1JkRvp2C...sp=sharing