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Old 30th November 2006, 08:19 PM   #1
BradNad is offline BradNad  United Kingdom
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Default Cambridge Audio A3i Relay

The output relay on my Cambridge A3i is on its way out. It lies at the back of the power amp board near the speaker outputs.

It has Cambridge Audio on it. Does anyone know which relay would work? It looks to have four soldering tails and switches both left and right channel on and off and forms part of the muting and speaker protection circuit.
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Old 30th November 2006, 11:06 PM   #2
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could you post a pin-out drawing with measurements between pins. I'll research possible parts over here.
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Old 20th April 2008, 06:22 PM   #3
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Relay in Cambridge Audio A3i

The relay coil has a DC resistance of ca. 1000 Ohms(in an A3i that I'm in process of repairing at least) and is a DPCO type. Most Component suppliers should stock a suitable device, although I haven't checked, and it will probably cost less from the likes of RS, CPC, Maplin, Radio Shack, etc., than the 'official' spare part from Cambridge Audio(if it's still available from them!) A Maplin store near to where you live may stock a suitable relay.
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Old 21st April 2008, 01:10 AM   #4
x-pro is offline x-pro  United Kingdom
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This relay should be fine:

http://uk.rs-online.com/web/search/s...duct&R=2563654

x-pro
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Old 21st April 2008, 02:54 PM   #5
BradNad is offline BradNad  United Kingdom
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Thanks for the replies. I know x-pro was the designer of the amp, thanks for the input.

However, the amp got very hot and went bang a few months ago, and does not even power up anymore.

I have owned 2 A3i's, and both of them ended up doing this.
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Old 21st April 2008, 03:58 PM   #6
x-pro is offline x-pro  United Kingdom
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Quote:
Originally posted by BradNad
However, the amp got very hot and went bang a few months ago, and does not even power up anymore.

I have owned 2 A3i's, and both of them ended up doing this.
Unfortunately, the build and some components quality were really poor, plus the original circuit was designed to be 40 W amplifier and than by a management decision was promoted to 60W just by increasing the supply voltage. Two things combined made for a poor reliability. I can supply you the circuit diagrams for A3i plus some suggestions how to improve it - in a little while. I've purchased an old A3i from ebay recently to rebuild and modify it, so I could publish an update guide on the web. The circuit in that amp is quite capable and uniquie, so I thought that I should do this update for my old design.

Cheers

Alex
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Old 21st April 2008, 05:17 PM   #7
OXAUDIO is offline OXAUDIO  United Kingdom
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Quote:
Originally posted by x-pro


Unfortunately, the build and some components quality were really poor, plus the original circuit was designed to be 40 W amplifier and than by a management decision was promoted to 60W just by increasing the supply voltage. Two things combined made for a poor reliability. I can supply you the circuit diagrams for A3i plus some suggestions how to improve it - in a little while. I've purchased an old A3i from ebay recently to rebuild and modify it, so I could publish an update guide on the web. The circuit in that amp is quite capable and uniquie, so I thought that I should do this update for my old design.

Cheers

Alex
21/04/08 4.06PM GMT

Alex,
Would you mind supplying me with a circuit diagram, and any other useful information on the A3i. I am in the process of repairing one in which Q14(2SA1216) had failed(Base/Collector s/c). Having replaced both O/P Transistors in that channel, and checked other components, I find that, after a few minutes, the relay trips out, the centre rail rises to ca. +26v, and LED2 goes out. Would I be correct in thinking that Q7 & Q8 are at fault, and, if so, with what should I relpace Q7? The type No. looks like ZVB330 to me, and that's not in any Data Book I have.
Incidentally on all the PCBs in the A3i which I have it states 'Copyright Michael Creek, 1996'
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Old 21st April 2008, 05:44 PM   #8
x-pro is offline x-pro  United Kingdom
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Quote:
Originally posted by OXAUDIO


21/04/08 4.06PM GMT

Alex,
Would you mind supplying me with a circuit diagram, and any other useful information on the A3i. I am in the process of repairing one in which Q14(2SA1216) had failed(Base/Collector s/c). Having replaced both O/P Transistors in that channel, and checked other components, I find that, after a few minutes, the relay trips out, the centre rail rises to ca. +26v, and LED2 goes out. Would I be correct in thinking that Q7 & Q8 are at fault, and, if so, with what should I relpace Q7? The type No. looks like ZVB330 to me, and that's not in any Data Book I have.
Hi,

I've emailed you through the forum and on reply will send you the diagrams. Most likely the LED2 itself is at fault - just replace it first with a good quality green LED, lifting it at least 15 mm of the PCB. Mind the polarity! If it is the transistor (also possible, thought less likely) the correct type is ZVP3306A from Zetex, available from Farnell:

http://uk.farnell.com/9524851/semico...ZETEX-ZVP3306A

Quote:
Originally posted by OXAUDIO
Incidentally on all the PCBs in the A3i which I have it states 'Copyright Michael Creek, 1996'
In 1996 I was working for Creek Audio and Michael was my boss . That does not change the fact that I've designed all electronics in that amp, including the PCB layout.

Cheers

Alex
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Old 21st April 2008, 08:01 PM   #9
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Cambridge Audio A3i Schematics

Alex.
Thanks for your prompt reply and the info. re Q7. I have now downloaded the diagrams, which, with your advice, should help me to get the amp. working again. It seems, from reading other posts on this forum, that these amps have been prone to failure, due mainly to poor build quality and (sometimes) poor components, so I will recheck everything carefully.
Michael('OXAUDIO')
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Old 22nd April 2008, 03:49 PM   #10
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Hi X-pro

Ive seen your thread on the mosfet vas, and played around in it with in lt spice. Very interesting topology with good results congrats. i dont have much experience with spice yet( learning now) and would like to ask if you have spice models on the mosfets(zvp3306 or zvp3310). I tried using the models from zetex but they dont seem to work with lt spice.

Thanks
Alexandre (also call me Alex)
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