I picked up an old AC/DC buzzbox the other day. It's branded Airco and has a red
case, but it's a Miller Thunderbolt AC/DC. It's probably from 1980 or so. I
started testing it and it was welding fine but suddenly the box started buzzing
much louder than before and it won't weld worth beans any more. I haven't taken
it apart yet. I figure something could be shorted to ground (although the 30A
mains fuse didn't blow) or whatever holds the transformer laminations together
might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington

Is it pooched in both a/c and d/c?
JR
Dweller in the cellar

Grant Erwin wrote:
I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly
the box started buzzing much louder than before and it won't weld worth
beans any more. I haven't taken it apart yet. I figure something could
be shorted to ground (although the 30A mains fuse didn't blow) or
whatever holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington


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Look for a loose connection. I've fixed lots of welders that needed nothing
more than a new lug or a connection tightened. You did not mention smoke
escaping or internal arcing so look at your connections.

Pete


"Grant Erwin" wrote in message
...
I picked up an old AC/DC buzzbox the other day. It's branded Airco and has
a red case, but it's a Miller Thunderbolt AC/DC. It's probably from 1980 or
so. I started testing it and it was welding fine but suddenly the box
started buzzing much louder than before and it won't weld worth beans any
more. I haven't taken it apart yet. I figure something could be shorted to
ground (although the 30A mains fuse didn't blow) or whatever holds the
transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this
one.

Grant Erwin
Kirkland, Washington

JR North wrote:
Is it pooched in both a/c and d/c?

It buzzes loudly regardless of whether any leads are plugged in at all.

If it had any capacitors I'd guess they shorted. But it doesn't. I'll pull the
cover as soon as I can.

GWE

Grant Erwin wrote:
I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly
the box started buzzing much louder than before and it won't weld worth
beans any more. I haven't taken it apart yet. I figure something could
be shorted to ground (although the 30A mains fuse didn't blow) or
whatever holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington

My guess would be a shorted diode, assuming the diodes are always in the
circuit. Second guess would be a shorted secondary winding in the
transformer or a short to ground, either in the transformer or a lead
shorted to the cabinet.

John

Sounds like it burned through some insulation and made some shorted
turns. Those boxes are only good for a 40% duty cycle and overheating
ruins the winding insulation.
Probably need to chuck it or try DIY rewinding.
Bugs

On Fri, 12 Aug 2005 20:16:53 -0700, Grant Erwin
wrote:

I picked up an old AC/DC buzzbox the other day. It's branded Airco and has a red
case, but it's a Miller Thunderbolt AC/DC. It's probably from 1980 or so. I
started testing it and it was welding fine but suddenly the box started buzzing
much louder than before and it won't weld worth beans any more. I haven't taken
it apart yet. I figure something could be shorted to ground (although the 30A
mains fuse didn't blow) or whatever holds the transformer laminations together
might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington

Pop the case and look on the right side for a main bus ribbon that has
melted in half.

Gunner

If it has the many turn crank on the front, check to see if the magnetic
shunt has broken away from the crank. If it does, the shunt will pull
all the way into the core, sets the welder for the lowest possible
amperage, and buzzes like the devil.

Grant Erwin wrote:
I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly
the box started buzzing much louder than before and it won't weld worth
beans any more. I haven't taken it apart yet. I figure something could
be shorted to ground (although the 30A mains fuse didn't blow) or
whatever holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington

On Sat, 13 Aug 2005 14:42:33 GMT, RoyJ wrote:

If it has the many turn crank on the front, check to see if the magnetic
shunt has broken away from the crank. If it does, the shunt will pull
all the way into the core, sets the welder for the lowest possible
amperage, and buzzes like the devil.


oooo..yah...that could be it!

Gunner

Grant Erwin wrote:
I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly
the box started buzzing much louder than before and it won't weld worth
beans any more. I haven't taken it apart yet. I figure something could
be shorted to ground (although the 30A mains fuse didn't blow) or
whatever holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington

I had the pleasure of trying to keep such a machine going in a school many
years ago. I ordered new guides and parts for the crank screw assembly to
firm up the movable core. It improbved it a bit but the machine had run so
much rod at rates well over the duty cycle that I was very happy to see it
replaced with a 300 amp dialarc.
Randy
"RoyJ" wrote in message
nk.net...
If it has the many turn crank on the front, check to see if the magnetic
shunt has broken away from the crank. If it does, the shunt will pull all
the way into the core, sets the welder for the lowest possible amperage,
and buzzes like the devil.

Grant Erwin wrote:
I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly the
box started buzzing much louder than before and it won't weld worth beans
any more. I haven't taken it apart yet. I figure something could be
shorted to ground (although the 30A mains fuse didn't blow) or whatever
holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this
one.

Grant Erwin
Kirkland, Washington

Mine was $5 a yard sale. had to fix the ball joint that attaches the
screw to the shunt assembly. Works fine, albeit a bit noisy.

Randy Zimmerman wrote:
I had the pleasure of trying to keep such a machine going in a school many
years ago. I ordered new guides and parts for the crank screw assembly to
firm up the movable core. It improbved it a bit but the machine had run so
much rod at rates well over the duty cycle that I was very happy to see it
replaced with a 300 amp dialarc.
Randy
"RoyJ" wrote in message
nk.net...

If it has the many turn crank on the front, check to see if the magnetic
shunt has broken away from the crank. If it does, the shunt will pull all
the way into the core, sets the welder for the lowest possible amperage,
and buzzes like the devil.

Grant Erwin wrote:

I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly the
box started buzzing much louder than before and it won't weld worth beans
any more. I haven't taken it apart yet. I figure something could be
shorted to ground (although the 30A mains fuse didn't blow) or whatever
holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this
one.

Grant Erwin
Kirkland, Washington

Grant Erwin wrote:
I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly
the box started buzzing much louder than before and it won't weld worth
beans any more. I haven't taken it apart yet. I figure something could
be shorted to ground (although the 30A mains fuse didn't blow) or
whatever holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this one.

Grant Erwin
Kirkland, Washington
Is it a arc point to point that wore down and once jumped it makes plasma and dumps.
Might be a matter of adjusting for the wear of he points so it does it normally.

Just a thought - might be it. Can't think of the 'real name' it is a
gross form of a regulator.

Martin

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Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
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NRA Second Amendment Task Force Charter Founder

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I tore it down today. First I ran the shunt all the way down and back up again,
then I wiggled every heavy wire. All looked good. So I plugged it in and no more
bad buzz. Didn't try running a bead yet, but the main symptom has gone. Rules
out a shorted diode. If it starts again when I'm actually running a bead, I'll
figure it's a thermal related issue with a transformer winding. Thanks for all
the tips, excellent help!

GWE

Randy Zimmerman wrote:

I had the pleasure of trying to keep such a machine going in a school many
years ago. I ordered new guides and parts for the crank screw assembly to
firm up the movable core. It improbved it a bit but the machine had run so
much rod at rates well over the duty cycle that I was very happy to see it
replaced with a 300 amp dialarc.
Randy
"RoyJ" wrote in message
nk.net...

If it has the many turn crank on the front, check to see if the magnetic
shunt has broken away from the crank. If it does, the shunt will pull all
the way into the core, sets the welder for the lowest possible amperage,
and buzzes like the devil.

Grant Erwin wrote:

I picked up an old AC/DC buzzbox the other day. It's branded Airco and
has a red case, but it's a Miller Thunderbolt AC/DC. It's probably from
1980 or so. I started testing it and it was welding fine but suddenly the
box started buzzing much louder than before and it won't weld worth beans
any more. I haven't taken it apart yet. I figure something could be
shorted to ground (although the 30A mains fuse didn't blow) or whatever
holds the transformer laminations together might have cracked.

Anyone got any bright ideas what to look for? I'd like to salvage this
one.

Grant Erwin
Kirkland, Washington