Half rail voltage QUAD 303

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Hi,
Prepares me to fix a problem that has got on my QUAD 303 amplifier. it is about the half-rail voltage in the driver boards, both right and left. I measured it (pin 9 and 5) and its the same that the rail voltage (pin 1 and 9) = 67volt. before i start with troubleshooting wanted to ask you about how I should connect a bench DC power supply with current limitation ( 200, 400, 800mA) to this driver boards. should i connect it to pins 1 and 9 or should i use pins 1 and 10? and which current limitation shoud I select?
Thank you,
Richar
 
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Joined 2010
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Hi.
Pin10 is the signal ground connection. R115 would likely overheat if you powered the amplifier from the front end so don't do this. When you normally power any amplifier that has a a voltage problem, always use a current limiting device such as a DBT (dim bulb tester) which is simply an incandescent lightbulb in series with the AC mains supply.

A DC bench supply can be used but the regulator board that connects to pins 12, 15 must be included so that the DC level at the output capacitor (5) can be set at half supply voltage. The service manual details the operation, setup and test procedure for this model. There's a free download available after signup here: Quad 303 - Manual - Stereo Power Amplifier - HiFi Engine
 
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