Part 4 - Chassis assembly



This page shows how to use the pre-punched chassis (shown above) that comes with the Time saver version of the SE-5a. If you bought the Basic version of the kit, you will have your own chassis, so use these pictures and instructions as a general guide.


Power transformer

The outside of the pre-punched chassis is covered with a protective plastic film; peel it off before you start. Then fit the power transformer - it mounts through the large rectangular cut-out that's surrounded by four M4 screw holes. Undo the four nuts and remove the fixing hardware from the underside of the transformer: one shakeproof washer, one plain steel washer and then the red fibre washer. Mount the transformer on the chassis' top surface, sliding the solder lugs through the rectangular hole.
      The power transformer can go either way around, but it's probably best to have the mains-related solder lugs (0-120 and 0-120) closer to the front of the chassis. This will help you make neater cable runs. With this transformer in place, refit all of the fixing hardware in the same order. So, the red fibre washer will be against the chassis, then the plain steel washer fits on top of that, then the shakeproof washer and finally the nut. Tighten the four nuts fully.

The PT mounts through the large rectangular hole on the chassis; use its own M4 hardware


Output transformer

The output transformer runs across the chassis (from front to back), and is almost in the centre. It mounts using two of the three 4mm holes (the two that are shown circled red in the picture below).


      Use M4 screws, shakeproof washers and nuts, and turn the transformer so that its solder lugs are facing towards the power transformer. Then fit a rubber grommet into the 10mm hole that's just to the side of the output transformer, close to these lugs.

Use M4 hardware to secure the output transformer, and add the rubber grommet to the hole next to the transformer


Valve sockets

The pre-punched chassis has five valve socket holes (numbered 1-5 in the photo, right). The SE-5a uses two of these for the ECC83 and EL84 valves. Add the first 9-pin valve socket to position 1, using the base of the valve shield. Rotate the ceramic socket so that the gap between pins 1 and 9 is towards the front of the chassis and use M2.5 screws and nuts with M3 shakeproof washers to secure the base.
      The socket for the EL84 goes in position 3 of the five holes, and uses the retaining clip to secure its socket to the chassis. Use the same combination of hardware to fix the clip and socket. Then fit the black hole covers to the remaining three socket holes.




Use holes 1 and 3 for the SE-5a's ECC83 and EL84 valve sockets


Orientate the sockets so that the gap between pins 1 and 9 is towards the front of the chassis


The spring clip will hold the EL84 in place, and will also act as a reminder of which valve fits into the SE-5a's two sockets


Front panel controls

There are five pots (variable resistors), two switches, a neon indicator and a jack socket to mount on the front of the chassis. They mount through your kit's silver anodised control panel and hold the panel in place.
      Start by adding the outer two components - the On/Off (DPDT) switch and the Input jack socket. There's a small amount of tolerance so use it to line the other hole positions up before tightening the nuts up fully. Then add the other controls:
* Neon indicator - so that the two solder lugs are easily accessible
* Standby switch - so that the two solder lugs are closest to the open side of the chassis
* Pots - so that the solder lugs also face the open side of the chassis. See Mounting the pots, right for extra details
* Knobs - with the pots fitted and tightened, fit the chickenhead knobs. To do this, first rotate each so that when the pot shaft is set to minimum (anti-clockwise), the head of the knob points to '0' (zero) on the dial. Fix in position by tightening each knob's set screw.

Mounting the pots

The pots are a general purpose type, and there are a couple of adjustments to make before fitting them. First, bend back the small forward-projecting tab (A) so that the pot can sit flush against the chassis. Then trim the soft nylon shaft of the pot to about 8mm (B), using a Dremel-type tool or junior hacksaw to cut it to size.
      Make sure to fit the correct pot in the correct position:
* Gain - VR1 is a 1M Log pot
* Treble - VR2 is the 220k Lin pot
* Middle - VR4 is the 22k Lin pot
* Bass - VR3 is a 1M Log pot
* Master - VR5 is a 1M Log pot


Rear panel parts

Fix the rear control panel into place by using M2.5 hardware for the small hole at one end and the IEC socket (with its two countersunk M3 screws) at the other end. Use the slight tolerance to line up the other three holes before fully tightening these nuts.
      Add the two speaker sockets, so that the solder lugs face the open side of the chassis. Add the fuseholder (which already has its fuse installed); it has a D-profile hole for anti-rotation, so can only be fitted in one position.


The fuseholder has a D-profile and can only be inserted one way round


Solder lugs for grounding

There are four 4mm holes for grounding lugs placed around the chassis. The first is close to the IEC socket. Use M4 screw, shakeproof washer and nut to fix a solder lug in place here, bending the 'arm' of the lug upwards (shown right) - to make easy access when you later add the wiring.
      The second grounding lug goes in the hole close to the 8-ohm speaker socket, the third is close to the Input socket and the fourth is close to the Standby switch.
      Now your chassis will look like this (below). Double check that all controls are in place and aligned as described above before proceeding.


The solder lugs are used for grounding, bend the arm of each lug so that its hole is accessible for soldering


  SE-5a construction guide
  1 - Kit contents
  2 - Block diagram
  3 - Reading your schematic
  4 - Chassis assembly
  5 - Turret board assembly
  6 - Turret board wiring
  7 - Chassis wiring guide I
  8 - Chassis wiring guide II
  9 - Chassis wiring guide III
  10 - Initial testing
  11 - Final test

  Main diagrams:
  Schematic
  Control panel wiring
  Turret board layout
  Turret board wiring
  Test-point diagram
  Final chassis picture

  SE-5a kit purchase page

  SE-5a construction guide
  1 - Kit contents
  2 - Block diagram
  3 - Reading your schematic
  4 - Chassis assembly
  5 - Turret board assembly
  6 - Turret board wiring
  7 - Chassis wiring guide I
  8 - Chassis wiring guide II
  9 - Chassis wiring guide III
  10 - Initial testing
  11 - Final test

  Main diagrams:
  Schematic
  Control panel wiring
  Turret board layout
  Turret board wiring
  Test-point diagram
  Final chassis picture

  SE-5a kit purchase page