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Chris Firth
Moderator Group Joined: 16 May 2013 Location: Rossendale, UK Status: Offline Points: 1529 |
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Not with Mark Audio drivers fitted! The drive units are Alpair7 by the look of 'em |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Alps don't name their pots "Blue Velvet". I believe you are referring to an Alps RK27. The Bitzie uses an Alps RK09. The plastic on the RK27 is blue and on the RK09 green. Neither use velvet. Both (like most pots) have carbon elements deposited on SRBP by silk-screen process, and some end-resistance tolerance is allowed because of registration error. The larger the print, the smaller the percentage of error. The tolerances are given by Alps in their data sheets. As most parts are riveted or pressed together there will be errors within tolerance here too. Wipers (which output the set volume or level) are formed from thin metal sheet having spring properties such as phosphor or beryllium bronze. Each wiper is often divided into a number of wiper fingers to reduce the possibility of the track lifting - or bouncing - when operated quickly. The AC27 wipers are divided into 5, and smaller diameter pots have wipers divided into 3 or 2 wiper fingers. Over extended use, parts can wear out and the wipers can loose their springiness. DC offsets are not all that well tolerated on the RK27 (see data sheet). The elements may become loose and go slightly out of position, and this might be the cause of Ifor's problem. If the "ground" connection was lost, that channel would most likely fail to full volume. |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Dave Friday
Senior Member Joined: 07 Apr 2011 Location: Spain Status: Offline Points: 173 |
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The earthy end of the volume controls could have a low resistance " dry joint".
But as you say Graham the crimping at the ends of the carbon track could be poor/ loose. I have two 10 k pots that had that problem! |
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lp12,oc9mk3,ca610p,krimson40watt pa,kef105.4
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marshmid
Senior Member Joined: 10 Feb 2013 Location: Scotland Status: Offline Points: 136 |
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If the above suggestions do not solve the problem, I successfully replaced a faulty volume pot on a Cambridge P50 amplifier. Neither air or cleaning fluid improved it. The amp was worth next to nothing and the Alps pot was about £15 (maybe less) so it wasn't a difficult decision. There was a good clearance around the pot so the job was not difficult.
I do not have the soldering skill to build a Genera! However, more modern amps may have limited clearance or be surface mounted? |
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ICL1P
Senior Member Joined: 04 Aug 2012 Location: Faringdon, Oxon Status: Offline Points: 2341 |
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It's certainly not a big enough problem to send it back to the manufacturer for repair. It is several years old and I bought it second hand. Sometime soon I'll open it up and have a look. With my new found confidence and skills, I might even be tempted to replace it myself as Marsh did.
Thanks everyone.
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Ifor
===== Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair. |
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ICL1P
Senior Member Joined: 04 Aug 2012 Location: Faringdon, Oxon Status: Offline Points: 2341 |
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Interestingly zero volume is noticeably louder with the FH3s (Mark Audio Alpair 7.3), SPL 85.8 dB than with the Spendor A5s, SPL 86 dB.
Edited by ICL1P - 21 Jan 2015 at 6:14pm |
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Ifor
===== Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair. |
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ServerBaboon
Senior Member Joined: 16 Jan 2008 Location: NW England Status: Offline Points: 968 |
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Does the crossover in the Spenders make the difference since there is non in the frugal?
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Steve
------------- Various bits of GSP Kit ..well two so far, unless you count the cables that is. |
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