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 ~ Schematic Diagrams & Service Information ~

The following is a list of Valve and some classic transistor equipment schematic diagrams and some service information

To increase clarity and or reduce the file sizes some have been traced redrawn and output in Adobe Acrobat pdf format

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Where possible I redraw schematics in the original style and layout so there may be a few inaccuracies ~ please let me know and I will correct them ~ Where components are concerned I generally use common symbols for basic parts i.e. an electrolytic capacitor is drawn in the old British style and looks like where the shaded end is negative ~ The American symbol would be where the curved side is negative

I have elected to use the British symbol for many redrawn schematics ~ Resistors are drawn which is common to nearly all older schematics and looks like a difficult path for current or even a heating element which is actually what it is! ~ The box symbol indicates nothing but I use it for the day job and some schematics that I produced for this site using my shematic and analysis software

Another area to look out for is junctions ~ most older schematics used bridges to show wires that cross later becoming a simple cross + where Junctions are marked with dots ~ As a rule however drawn no more than 3 wires should meet at a junction ~ I use bridges or simple crosses with junction dots (often coloured differently in EDA) and more than 3 wires at junctions if it reflects the original style and is obvious how connected

Schematic
Additional information and source links
Customer repair ~ Drawing supplied with repaired amp ~ All part of the service
Beard Audio P35 valve power amp circuit modified to remove d.c. input coupling and the problem active bias circuit ~ parallel valve amplifiers need good output transformers and separate resistor biasing helps prevent them melting down
Beard Audio P35–M70 Beard Audio P35 and M70 Valve power amplifier circuit diagram derived from a scrappy old schematic as sold at an excessive price by BeardAudio.com or is it .uk ~ which my friend Chris Found without the aid of a copyright lawyer ~ Share and enjoy
BUSH TR130 130D BUSH Tr130 B818 Transistor Radio Service Information ~ Alignment and Repair
Hafler and Keroes valve amp schematic from Audio Engineering 1951 in searchable and scaleable pdf
Valve amplifier schematic from 1947 Wireless World Article by D.T.N. Williamson
Schematic from 1949 Wireless World Article New Version by D.T.N. Williamson
From the QUAD II handbook redrawn in the original style
Relaid for PSPICE Analysis giving a different perspective on the circuit operation
Traced from a "Concordant" modified QUAD II before being put back to standard
Scan from drawing supplied with original handbook
Redrawn on A4 but as scaleable and searchable pdf file
A Compilation of redrawn QUAD 405 circuit diagrams covering all production versions plus some Keith Snook mods ~ Use as a "flick book" to see the changes
pdf version of the original QUAD 405 and 405-2 service data
Schematic to support 405 Article non inverting input stage modification
Scanned copy QUAD 606 power amplifier schematic
pdf of scan (A3 size) for s/n 11,000 onward
QUAD 34 Pre-amp schematic redrawn to support QUAD 34 Mods
To support my article QUAD 34 Mods Moving coil Disc input schematics
QUAD MPX Decoder To suppport my article QUAD FM1 Stereo MPX decoder Silicon transistor mod
To support the article ~ Loud Speakers/LS3/5A external crossover modification
To support the article ~ Loud Speakers/BBC LS3/5A
Passive tone control modification for this 1970s "Marshall" copy amp
This information is offered for free and without warranty ~ Take note Beard audio and Mauritron Services ~ If you intend to use this information for commercial use certain laws may apply in some parts of the world ~ Otherwise Share and Enjoy ~ And please be careful not to electrocute yourself

The map is not the territory

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"I recall when I was small ~ how I spent my days alone"