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~ Schematic Diagrams & Service Information ~
The following is a list of Valve and some classic Transistor equipment schematic diagrams and 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 symbols 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
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 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 "