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Ashdown audio band amps - generic fault

For factory retro-fitted fans.

3 faults in one just fitting a fan and power bleedoff

For random fan stoppage - look for Instead of 47R 5W W/W placed in line with the fan (dangling R unsupported at one end) , 0.047R soldered-in so 21V across the 12V fan. Surprisingly thousands of hours of unproblematic use like that.

Even without that , for any long term excessive wear on the bearing of fan , the reaction force pushes the impeller towards the mounting bracket, eventually touching it. You could see a slight trace of where one fan vane had rubbed the bracket and rubbed the plastic of that vane, ie clear of usual gunge.

Replace with 47R, supported, and new fan with the centre section of the mounting bracket hacksawed out.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook
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Fourth mistake : the fan just circulates the air internally, no added baffles to duct air in from outside. So air heats up, softens fan's plastic vanes , vanes flex a bit, to the extent of touching the mount.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

What do you expect? it`s a Trashdown!

;)

Ron

Reply to
Ron(UK)

unsupported

fan

vane

Up till today I assumed they were no better or no worse than any other make.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

unsupported

fan

vane

I was aware, a long time ago, that WEM was short for Works Every Monday

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

I just thought of a fifth problem. With the fan , as original, directing internal air down the long axis of the fan. The big toroidal would split the air flow at the other end , returning back to the fan along the outer edges. As no pressure differential between inside and outside of box , the vents in the base and rear become useless as any thermal gradient across the box is lost.

A baffle now added arounfd the fan to take air from outside, through some of the vents, and direct it back out through the remaining vents.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

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