Marshall 18 Watt
Amp Board and Layout

!!!CAUTION: TUBE AMPLIFIERS CONTAIN LETHAL VOLTAGES EVEN WHEN UNPLUGGED!!!

Table of Contents

 
  SAFTY READ FIRST  

 
  18 watt Lite Layout w/EZ81

  18 watt Lite board

  18 watt tremolo board

  18 watt Pro Jr. Layout

  18 watt Lite Layout w/diodes

  Pictures

  New 18 watts for Pro Jr. PDF!

  18 watt Full Schematic PDF

  Home


HIGH VOLTAGES CAN KILL YOU - ALWAYS WORK SAFE!
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You have to understand how to safely work inside the chassis of a tube amp. Just reading this is not enough, but here are a few tips: Never work on a amplifier that is plugged into the wall socket, always unplug it first! Stand on a rubber mat of some sort and don't work bare foot, under the influence of alcohol or any other drug, legal or not for that matter. Here is another good tip: Only probe an amp with you're right hand and with you're left hand by you're side. So if you do happen to take a high voltage shock, the the voltage will not go across you're chest!

High Voltage is stored in the electrolitic capacitors and they need to be discharged!That's what I'm doing in this pic. These are those large round can's and there usually blue or black. The discharge tool is made of 600 Volt wire with a 3-5 watt resistor of 500 to 1000 ohms. Basically you clip one side to ground then clip the other end to the Pos + side of the capacitor. If I have two cans as seen here then there are actually 4 capacitors 2 in each can, so I will take the time and clamp the discharge tool on all 4. Some cans can have more that 2 as well. Check with you're multimeter set to 600 DC volt setting and make sure the voltage has been fully discharged.

Please read through these two Links:

How much voltage can kill?
A Must Read!

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18 Watt Board
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One of my earlier builds, though this was my first chassis that I built. I have never bought a chassis yet.

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18 Watt Tremolo Board
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18 watt Tremolo Board in Vintage Red Swirl

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18 Watt Layout for Pro Jr.
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Missing from this layout is the power transformer, fuse, power switch, output transformer and speaker outputs.
V1 and V2 are the pre-amp tubes 12AX7 or of that type, and V3 and V4 are the larger EL84 power tubes.

This is not for a novice, you have to have some background with tube amps and electrical skills!

PDF Layout

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18 Watt Lite Layout - Diodes
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This is the schematic used in my home brew seen below.
Missing from this layout is the power transformer, fuse, power switch, output transformer and speaker outputs.
V1 and V2 are the pre-amp tubes 12AX7 or of that type, and V3 and V4 are the larger EL84 power tubes.

This is not for a novice, you have to have some background with tube amps and electrical skills!

PDF Layout

  18watt lite Schematic

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18 Watt Lite Layout - EZ81
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Missing from this layout is the Output Transformer, and speaker outputs.
V1 and V2 are the pre-amp tubes 12AX7 or of that type,
V3 and V4 are the larger EL84 power tubes
V5 is a EZ81 Rectifier Tube.
This is not for a novice, you have to have some background with tube amps and electrical skills!

PDF Layout

  18watt lite Schematic

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18watt pics
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Copyright © 2005-2006 by Robert Souza. All rights reserved.