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While repairing a Marantz amplifier using the service manual, I came across resistors with odd symbols (see page 18). They are trapped between two parallel lines (for example, 3297).

Is this linked to the fact that this is a 0.33W resistor? A comment suggested it could be related to the way it's mounted to the board for heat dissipation, but I don't see any mounting difference between 3297 and 3283 (see picture below).

Furthermore, what's the difference between the "R" and "E" letters for 3293 & 3305. Don't they both mean "Ohm" ? Is there any reason for Marantz to use both notations in this diagram or is it just an inconsistency?

Marantz PM-68 Main circuit left amp +56V Marantz PM-68 Main circuit photography Marantz PM-68 disassembled

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  • \$\begingroup\$ Check electronics.stackexchange.com/questions/246920/…. Weird they use both in the same schematic. \$\endgroup\$ – Huisman Mar 28 '19 at 9:56
  • \$\begingroup\$ That's why it bothers me. Why would they use both if they mean exactly the same thing? \$\endgroup\$ – MFlop Mar 28 '19 at 10:10
  • \$\begingroup\$ Possible duplicate of What is a "100R" resistor? \$\endgroup\$ – C. K. Mar 28 '19 at 10:11
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    \$\begingroup\$ @MariusGulbrandsen : I'm just bothered by the fact they used both notations. The main question was about the two parallel lines for 3297. \$\endgroup\$ – MFlop Mar 28 '19 at 10:15
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    \$\begingroup\$ @soosaisteven Don't write answers in the comment section. No one can interact with them, and OP can't mark anything as accepted. \$\endgroup\$ – pipe Mar 28 '19 at 16:12
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I came across resistors with odd symbols (see page 18). They are trapped between two parallel lines (for example, 3297).

crop from schematic supplied in the question, showing the unknown resistor symbol

(Crop from the original schematic, showing the unknown resistor symbol.)


Answer: That is one of the (many) symbols used for a fusible resistor. Here is an extract from page 177 in the book: Electronics for Service Engineers by Joe Cieszynski and David Fox (Google Books link to page 177) showing that symbol, which I've marked in red below:

Figure 11.4 from "Electronics for Service Engineers" by Joe Cieszynski and David Fox

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