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Chris Firth View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris Firth Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 2015 at 3:49pm
Originally posted by BackinBlack BackinBlack wrote:

The Frugels are quite sensitive


Not with Mark Audio drivers fitted!
The drive units are Alpair7 by the look of 'em Wink
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Graham Slee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 2015 at 4:18pm
Originally posted by Ash Ash wrote:

(It's not a blue velvet)


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.
Not simple enough for Google-Bot to understand...
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Dave Friday View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave Friday Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 2015 at 5:16pm
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!
lp12,oc9mk3,ca610p,krimson40watt pa,kef105.4
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marshmid View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote marshmid Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 2015 at 5:35pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote ICL1P Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 2015 at 6:02pm
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.
Ifor
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Reflex M, CuSat50, Majestic DAC, a Proprius pair.
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ICL1P View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ICL1P Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 2015 at 6:13pm
Originally posted by Chris Firth Chris Firth wrote:

Originally posted by BackinBlack BackinBlack wrote:

The Frugels are quite sensitive


Not with Mark Audio drivers fitted!
The drive units are Alpair7 by the look of 'em Wink
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
Ifor
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Reflex M, CuSat50, Majestic DAC, a Proprius pair.
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ServerBaboon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ServerBaboon Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jan 2015 at 10:25pm
Does the crossover in the Spenders make the difference since there is non in the frugal?


Steve

-------------

Various bits of GSP Kit ..well two so far, unless you count the cables that is.
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