Creast CA9 Fault
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Category: General
Forum Name: Amp Forum
Forum Description: The 'Stopping Jake Fielder moaning constantly' forum description...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=58323
Printed Date: 27 March 2026 at 8:46am
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: Creast CA9 Fault
Posted By: 100 Volt-line
Subject: Creast CA9 Fault
Date Posted: 20 October 2011 at 12:16pm
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One for you amp repairers.......... Crest CA9 MK2 has a fault on left channel,the problem is it is very quiet. There is sound there, but it is quiet. The other side works fine. My first thoughts were towards a sticky selector switch for the bridge/parallel/stereo switch, but working this a few times has not remedied it. The fault persists in stereo and parallel mode, not tried bridge. Its not dodgy cables or anything, tried all that, the only thing that has happened recently is the fan on the faulty side jammed when I lent it to a mate for his disco. It went into protect (as it would) and was ok when it cooled down, so he says ! this happened a few times apparently, and him not being technical, never thuoght to un-jam the fan, or ring me ! Could this have done some damage ? My background is electrical not electronics, so i can get so far with fault finding, but am not too good with the real technical stuff. (bias voltages, bi polar transistors, negative feedback...all Chinese to me )I have a scope, but have never used it ! This amp has had very little use; more time stood than being used, that said, its never ever been faulty before. Any thoughts are appreciated. 100 Volt |
Replies:
Posted By: inge_am
Date Posted: 20 October 2011 at 9:27pm
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Hi, the sound of defective channel is only quiter or distorted too? Is it full bandwidth or with less low frequencies? Let me know. AM |
Posted By: 100 Volt-line
Date Posted: 21 October 2011 at 9:04am
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Hello It is just quieter, sounds full range. It just sounds like one side is turned down a lot, I have tried the input attenuator, and turning that down makes it even quieter (as it would). The signal LED barely flashes for this channel. Its probbably something simple ! |
Posted By: _djk_
Date Posted: 21 October 2011 at 9:18am
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Compare the attenuation voltages on IC4, pins 7 and 10. If the same, try replacing IC4, a NE5517D attenuator. ------------- djk |
Posted By: Pinyorouk
Date Posted: 21 October 2011 at 9:21am
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Hi, Sounds like there is a fault in the input section of the amp. Could be the input volume control or one of the components in the low level circuitry of the amplifier. Best bet would be to send it off to repair. If you were to semi dismantle it and accidentaly caused a short circuit the repair bill may quickly soar. Had you have had electronic experience I would have suggested that you use a signal generator and oscilloscope to trace the signal through the amplifier circuit starting from the input. As _DKJ_ mentioned, you could do a comparison of the correctly working amps signal levels at different points in the circuit.
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100 Volt-line wrote:Posted By: 100 Volt-line
Date Posted: 21 October 2011 at 4:14pm
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With a bit of swapping around, I have located the fault to the board that piggy backs the main board on the faulty channel. Thats about as far as I can go, so it looks like it needs to go for repair. I used to go to Audio Labs in Leeds, but they have retired and shut up shop, anyone know anywhere else in Yorkshire ? |
Posted By: service dept Steve
Date Posted: 21 October 2011 at 7:08pm
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I was going to suggest that you check the pre-amp boards (the ones you mentioned) because the favorite failure of these amps is that the connector partly disconnects leading to unpredictable behavior, I assume that you have swapped both boards and the fault has changed sides?
------------- We are not "They", We are "The others" http://www.servicedept.co.uk" rel="nofollow - http://www.servicedept.co.uk - |
Posted By: 100 Volt-line
Date Posted: 22 October 2011 at 10:19am
| Yes, thats right. I gave the pins a clean up just in case. Looks like its a repair job ! |
Posted By: service dept Steve
Date Posted: 23 October 2011 at 10:48am
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But you have swapped the boards and now the fault is on the other channel, right?
------------- We are not "They", We are "The others" http://www.servicedept.co.uk" rel="nofollow - http://www.servicedept.co.uk - |
Posted By: 100 Volt-line
Date Posted: 24 October 2011 at 11:58am
| Yes I have |
Posted By: G-Wakefield
Date Posted: 01 November 2011 at 12:59pm
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Abacus Electronics have taken up work from Audio Lab
http://www.abacuselectronics.co.uk/" rel="nofollow - http://www.abacuselectronics.co.uk/
Give him a call before turning up as he works from a garage at home and sometimes doesn't have room, may give you a day to drop off!!
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