Thats a job for a TIG or a Henrob mini gas torch and lots of patience, that
Alpha cover is thin. I use both when required and leave the MIG, arc and
old gas stuff for other heavier/less critical work.
Carl
KM1H
----- Original Message -----
From: "Jim Barber" <audioguy@q.com>
Cc: <amps@contesting.com>
Sent: Thursday, June 21, 2012 5:13 PM
Subject: Re: [Amps] Acoustic Noise Comparison
> I'd hate to warp the cover MIG welding, but then I'm no welder at all -
> just guessing.
> Also - just read your last... Angle stock would be stronger, but we're
> trying to dampen resonance. my seat-of-the-pant-ometer says flat bar
> would be perhaps just as effective and would have a flatter profile.
>
> I hate to admit this in public, but the last one I fiddled with I used
> 1/2" MDF in strips, first sealed with a 50% solution of yellow glue and
> water, then glued (press-clamp HARD) to the underside of the cover with
> Gorilla glue. I spent too much time "cutting and trying", but in the end
> it worked well and although I haven't heard that it's ever come off, it
> would be non-conductive if it did. I'm planning the same treatment for
> *my* QRO HF2500DX, which suffers from a cheap-but-easy-to-replace,
> solid-mounted Dayton blower and a huge sheet metal cover. That one's
> also getting an EBM-Papst ball-bearing unit with a cast housing,
> assuming I can make it fit.
>
> Just some ideas - there are some bright people that read this list,
> perhaps one or more of them will share a relevant experience.
>
> 73,
> Jim N7CXI
>
> On 6/21/2012 3:12 PM, Jerry Kaidor wrote:
>>> Spot on, Jim.
>>> The 76A and the 78 suffer from both vibration and turbulence, with the
>>> effects compounded by resonances in the sheet metal cover.
>> *** I do have some "Dynamat" left over from a car project. I might try
>> a few pieces of that stuck to the top & sides - in places where there's
>> nothing for it to short out if it comes loose - which doesn't seem very
>> likely; the stickum on Dynamat is extremely agressive. The casing is
>> pretty thick metal - but it sure does ring like a bell when you tap it.
>>
>>> Better blower mounting and fuzz would help a lot, a scattering of braces
>> *** By "braces" I assume you mean narrow strips of metal welded to the
>> case so they stand up at right angles to it? My cover has a couple real
>> good
>> scratches in the top, so it needs to be bodyworked anyway.
>> Unfortunately,
>> according to Mr. Magnet, it's aluminum. I do have a spool gun for my MIG
>> welder that's supposed to be able to weld aluminum, but I've never tried
>> it yet. And that's assuming it's a weldable *alloy*.
>>
>> The amp came to me without rear feet, so the back of the cabinet is
>> resting on the desk. I have ordered new feet from RF Concepts, along
>> with the new blower.
>>
>> - Jerry Kaidor
>>
>>
>>
>
>
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