~ 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

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 schematic 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
AcroSound 6L6 Rebuild	Customer repair ~ Drawing supplied with repaired amp ~ All part of the service
Beard Audio P35	Beard Audio P35 valve power amp circuit modified to remove the problem d.c. input coupling and the active bias circuit ~ parallel valve amplifiers need good output transformers which the original does not have ~ and separate resistor biasing helps prevent them melting down with inevitable valve mismatch
Beard Audio P35–M70	Beard Audio P35 and M70 Valve power amplifier circuit diagram derived from a scrappy old schematic previously sold at a stupid price ~ Share and enjoy
BUSH TR130 130D	BUSH Tr130 B818 Transistor Radio Service Information ~ Alignment and Repair
Ultra-Linear Amplifier	Hafler and Keroes valve amp schematic from Audio Engineering 1951 in searchable and scalable pdf
High Quality Amplifier	Valve amplifier schematic from 1947 Wireless World Article by D.T.N. Williamson
High Quality Amplifier	Schematic from 1949 Wireless World Article New Version by D.T.N. Williamson
QUAD II Amplifier	From the QUAD II handbook redrawn in the original style
QUAD II Amplifier	Relaid for PSPICE Analysis giving a different perspective on the circuit operation
"Concordant" QUAD	Traced from a Concordant modified QUAD II before being put back to standard
QUAD AM II Tuner	Scan from drawing supplied with original handbook
QUAD QC 22 pre-amp	Redrawn on A4 but as scalable and searchable pdf file
QUAD 22 RIAA PCB	My replacement PCB for an improved QUAD 22 'fixed' RIAA amplifier stage
QUAD 405 Evolution	A Compilation of redrawn QUAD 405 circuit diagrams covering all production versions plus some of my own mods ~ Use as a pdf "flick book" to see the changes
QUAD 405 Service Data	pdf version of the original QUAD 405 and 405-2 service data
QUAD 405 input stage	Schematic to support 405 Article non inverting input stage modification
QUAD 66FM	QUAD 66FM RF section ~ A3 pdf ~ Not the best
QUAD 606 service data	QUAD 606 power amplifier schematic
QUAD FM4	pdf of scan (A3 size) for s/n 11,000 onward
QUAD 34	QUAD 34 Pre-amp schematic redrawn to support QUAD 34 Mods
QUAD34 Moving Coil	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
11Ω LS3/5A modified	To support the article ~ Loud Speakers/LS3/5A external crossover modification
11Ω LS3/5A Standard	To support the article ~ Loud Speakers/BBC LS3/5A
SAI guitar amp	Passive tone control modification for this 1970s "Marshall" copy amp
Selmer TV8 & Mercury 5	1960s Guitar Amp ~ Mercury 5 is same as TruVoice 8 tremolo but has magic eye
This information is offered free and without warranty ~ If you intend to use this information for commercial use then certain laws may apply in some parts of the world ~ Otherwise Share and Enjoy ~ And please be careful not to electrocute yourself or others The Map is not the Territory

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