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The following is a list of Valve equipment and some classic transistor schematic diagrams.
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 have redrawn the following 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 have generally used common symbols for basic parts i.e. an electrolytic capacitor is drawn in the old British style and looks like I have elected to use the British symbol for redrawn schematics — Resistors are drawn Another area to look out for is junctions, most older schematics use bridges |
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Schematic
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Additional information and source links
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| Customer repair — Drawing supplied with returned amp — All part of the service | |
| Beard Audio P35 valve power amp circuit modified to remove d.c. input coupling and problem active bias circuit — My friend Chris found the original Beard M70 schematic | |
| Beard Audio P35 M70 Service Data download | Beard Audio P35 and M70 Valve power amplifier circuit diagram derived from a scrappy old schematic sold by Beard Audio redrwan to correct drawing error problem |
| Hafler and Keroes valve amp schematic from Audio Engineering 1951 in searchable and scaleable pdf | |
| Valve amp 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 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 article QUAD 34 Mods Moving coil Disc input schematics | |
| To support the article — Loud Speakers/LS3/5A external crossover modification | |
| To support article Loud Speakers/BBC LS3/5A | |
| Passive tone control modification for this 1970s "Marshall" copy amp | |
| Note: This information is offered for free and without warranty — 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 |
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"I recall when I was small ~ how I spent my days alone"
![[Download Acrobat Reader]](Schematics/getacro.gif){kind=small}
where the shaded end is negative — The American symbol would be 
where the curved side is negative
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 
to show wires that cross later becoming a simple cross + — Junctions are often marked with dots 
— As a rule however drawn no more than 3 wires should meet at a junction — I have elected to use bridges or simple crosses with junction dots (often coloured differently) and more than 3 wires at junctions if it reflects the original style and is obvious what is connected