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Quad 303 all versions illustrated upgrade guidelines V2.0 

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Quad 303 all versions illustrated upgrade guidelines V2.0 
Including installing HE boards 
 

These are the illustrated step-by-step guidelines for upgrading your Quad 303 with 
the Dada Electronics upgrade-kit. 
 

 

 
First of all, thanks for your purchase of our upgrade kit! Hereunder, you will find the 
step-by-step guidelines for upgrading the Quad 303 amplifier to modern, high-end 
standards. A word of advice: be sure to always watch the polarity of all diodes, 
zeners & electrolytic capacitors mentioned, and strictly follow the steps described in 
these guidelines!  
 
There are in fact three versions (as far as we now until now) of the Quad 303. The 
first two versions (up to serial no. 11500) have different driver boards. Make sure you 
use the schematic that corresponds with the version you have. You will find the 
schematics and the service manual in our download section, the information from the 
service manual and the diagrams will not be repeated in this manual. We cover all 
the versions with one kit. Only RV101 is different and will be delivered in two values! 
 
We do not advice to revise boards older than version 9, although it can be done, the 
quality of the boards is too low in most cases and there are circuit changes. Instead, 
purchase our HE boards or already revised version 10 boards. 

DaDa Electronics

Summary of Contents for 303

Page 1: ...teps described in these guidelines There are in fact three versions as far as we now until now of the Quad 303 The first two versions up to serial no 11500 have different driver boards Make sure you u...

Page 2: ...derlined and will provide for tips tricks and advice in italics You can obtain 7 7 technical support for upgrading the 303 via this e mail address Also make sure to check the Quad revision weblog regu...

Page 3: ...t have these tools they can be ordered from our Dada Electronics Webshop The 303 upgrade kit consists of 1x 4700 F 100V capacitor for the power supply 2x 6800 F or 4700uF 63V or 100V capacitors for t...

Page 4: ...apacitor 470 F 16V C104 Capacitor 22 F 25V C106 Capacitor 47 F 25V RV100 4K7 Trimmer potentiometer RV101 2K2 Trimmer potentiometer and 22K for the versions below serial 11500 Options available from ou...

Page 5: ...x 2000 F PSU capacitors in parallel with 1x 4700MF 100V Modern capacitors are a lot smaller and better than their 6 ties ancestors In some cases you may need to wind some self adhesive tape around the...

Page 6: ...ck brown brown Replace R206 with 10R brown black black gold brown Replace R207 with 68R blue grey black gold brown Replace MR200 with 1N4004 black with silver or white stripe Replace MR201 with a Zene...

Page 7: ...C104 with 22 F Replace C106 with 47 F Replace RV100 with a 4K7 trimmer Replace RV101 with a 2K2 trimmer or 22K in the case of version 9 or lower driver board Be advised watch the polarity of the elec...

Page 8: ...reen White Output to output capacitor 6 Blue White Collector of TR2 7 Orange White Base of TR2 8 Brown White Emitter of TR2 and negative Power Supply 9 Brown White LS These are for the left channel Th...

Page 9: ...river board Connect a multimeter between pins 4 and 6 on any of the driver boards Set the multimeter to its DC millivolt mV range Adapt RV101 until you measure at least 6 mV DC A somewhat higher value...

Page 10: ...board there is a two position switch with both switches off as in the picture the sensitivity is 0 5V standard 303 value with one switch on the sensitivity is 1V with both switches on the sensitivity...

Page 11: ...yout for a serial below 11500 2 Schematics refer to the download section of our webpage 3 Color coding of resistors 4 Identification of electrolyte capacitors diodes and zeners Layout of the driver bo...

Page 12: ...Quad 303 all versions illustrated upgrade guidelines V2 0 Page 12 of 14 M12038 Issue 5 and 9 boards in one 303 Graphic by Jose Ignacio Alfaro Allona D a D a E l e c t r o n i c s...

Page 13: ...s the third significant figure band D is the decimal multiplier band E indicates tolerance of value in percent Color A First figure B Second figure C Third figure D Multiplier E Tolerance Black 0 0 0...

Page 14: ...ipe indication or have indications on top of the capacitor if any doubts contact us Be aware connecting capacitors wrongly could cause serious damage or injuries With axial capacitors there is an extr...

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