Custom Sound Trucker 704
Another solid state head from the eighties, manufactured in the UK by Custom Sound SST Ltd in Oswestry, Shropshire.
Custom Sound seem to have picked up a reputation as a cheap and cheerful, budget brand, possibly through their association with FAL. There's nothing wrong with the design and performance of this one though. The cost saving starts to show up in the quality of the components, something you could say about a lot of the competition at the time.
There are some interesting discussions about the company's history in several places including;
mu:zines, facebook, UK Vintage Radio and Bass Buzz.
The original company was wound up in October 1982.
Odd things to look out for:
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The toggle switches on the front panel are prone to damage. They also suffer from dirty, intermittent contacts if they've been left in the same position for the last twenty years. Don't be fooled by a low reading with a multi-meter; the audio signal will still struggle. This one had a very low reverb level, completely cured by replaceing the switch.
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Noisy pots
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Someone had turned the output bias control (RV301 on the power board) fully clockwise, causing a nasty crossover distortion.
Front Panel:
Input HI
Input LO
Bright / Normal toggle switch
Bright / Normal footswitch socket
Gain
Reverb on/off toggle switch
EQ Section:
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Bass, Mid Lo, Mid Hi, Treble
Overtone
Overtone footswitch socket
Master Section:
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Reverb, Presence, Volume
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Reverb footswitch socket
Illuminated mains power on/off rocker switch
Rear Panel:
IEC mains input
Mains fuse 3amps
Output Fuse 5amps
Loudspeaker Outputs x2
Line / Tape Out
Slave Output
Headphone*
*The headphone output takes a 1/4" TRS jack plug.
Left and right channels are fed in parallel through a 470R resistor from the main power amp output.
Using the headphone jack disconnects the main speakers.
Measured output power:
100watts rms into 4ohms at clipping with a 1kHz sinewave.
IMPORTANT: These drawings and notes are provided for interest only and are not guaranteed to be accurate. Use at your own risk and discretion. The equipment shown contains lethal voltages and should only be worked on by people with suitable training and experience. Schematics and layouts are typical but will vary.
PRINTING
Wix (bless 'em 😖) have changed their image format - again - to avif just to make them awkward to print. Unless you want to buy a converter, the easiest way to make a hard copy is:
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Left click when the magnifying glass icon appears and wait for the picture to clear.
(On a touch screen, tap on the image). This will display a higher res file. -
Right click and 'save image as' to somewhere as an avif file.
(On a touch screen, touch and hold down to view the menu) -
Upload the saved file to your Google Drive.
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Open the file and use the print menu to make a hard copy or save as a pdf.
Custom Sound Trucker 704 General Layout
Custom Sound Trucker 704 Input Board Schematic
Custom Sound Trucker 704 Input Board Layout
Custom Sound Trucker 704 Master Board Schematic
Custom Sound Trucker 704 Master Board Layout
Custom Sound Trucker 704 Power Board Schematic
Custom Sound Trucker 704 Power Board Layout
