How to wire Marstran 103 OT to single Sp Jack @ 8ohms

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How to wire Marstran 103 OT to single Sp Jack @ 8ohms

Postby page361 » Wed Apr 18, 2012 12:28 pm

Greetings - I am building a JTM45 offset type chassis with single speaker jack and no ohm selector switch, hard wired for 8 ohms. I'm using a Marstran 1202-103 and hoping someone can confirm that the wiring outline below looks correct? Your review and guidance would be greatly appreciated - thanks!

Primary
• BLACK to V4
• RED to V5
• BROWN (Center Tap) – combined with choke wire and terminated to 32uf filter cap next to GZ

Secondary - single speaker jack wired for 8ohms
• GREEN (8 ohm) soldered to positive terminal of speaker jack
• ORANGE - (4 ohm) tucked under board
• BLUE (16 ohm) tucked under board
• YELLOW (Common) soldered to NEG term of speaker jack

• PURPLE wire between positive terminal of speaker jack to 27K feedback resistor on board
• Install ground wire (BLACK) between the negative terminal on speaker jack to V4 ground lug.
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Re: How to wire Marstran 103 OT to single Sp Jack @ 8ohms

Postby David B » Wed Apr 18, 2012 5:01 pm

Yeah that looks right though I like to leave my plate wires long just in case ya get the +FB squeal and need to swap them..

With that OT it wouldn’t be much trouble to throw in a rotary switch if you like..
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