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Old 20th April 2008, 09:42 AM   #1
OXAUDIO is offline OXAUDIO  United Kingdom
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Question Schematic for CambridgeAudio A3i

Does anyone have, or know where I can get, a scematic diagram/service manual for the above? The 2SA1216 in the LH Channel has failed(Base/Collector short-circuit). Having 'cold checked' and visually inspected other components, I replaced both output transistors(The NPN one is a 2SC2922) only to find that the centre rail, which should be 0v is about +25v w.r.t. ground. The relay and driver transistors check out OK 'cold'
Any suggestions as to what else needs replacing??
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Old 20th April 2008, 12:18 PM   #2
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east electronics's Avatar
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Default check drivers

also for short circuit and if this circuit includes clamp diodes check them also ....also check rail fuses to see if they are ok
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Old 20th April 2008, 01:24 PM   #3
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Cambridge Audio A3i Amplifier

The two 4amp fuses in the transformer secondary circuit had blown, due to the original fault. Replacement 4A(T) Fuses OK after amp was powered for a couple of minutes whislt checking it. The driver Transistors check OK 'cold', don't know about clamp diodes, though I will check for them, but a schematic would still be helpful, if one can be obtained. There are a number of green LEDs on the main amp PCB. Not certain what they are there for, but they all illuminate.
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Old 20th April 2008, 02:23 PM   #4
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I'm pretty sure there are more threads about this amp with input from the designer. At least two people in those threads offer a schematic.

The search button can be very useful sometimes.
+ + =
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Old 20th April 2008, 05:00 PM   #5
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Schematic for Cambridge Audio A3i

I had done a search before posting my request, but, unless I've missed something(quite possible!!) there are no threads on this forum relating specifically to the A3i Amplifier, which include a schematic diagram. I will have another look, however, in case something has appeared since this morning(UK Time)
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Old 21st January 2009, 07:35 AM   #6
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Hi there dont know if you fixed amp or not but also check the big resistors for open circuit and when the output blows normally takes the little black trim pot with it also ,,and replace all leds (green) these set up the current in amp.make sure they stand above board get hot...
if you strip it for parts keep them for years as soon as you get rid you will want them .....................
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Old 21st January 2009, 09:30 AM   #7
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Reply to post by 'homertooties'

I had actually fixed that amplifier sometime in April/May last year, having obtained a circuit diagram for it. In the end, from memory, I replaced at least one faulty LED(They, as you no doubt know, don't fail too often), and some other parts. After setting it up, I test ran it for several hours a day, then it went back to it's owner. So far as I know it's working fine to this day. Your post may help others having problems with Cambridge Amplifiers, though.
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