Recently my tower was hit by lightning. All my ham gear survived except
one. Since I forgot to unplug my Amp Supply LK-500ZB Linear Amp from the AC
power mains, the lightning found a nice way in.. (The rest of my ham gear
was disconnected from the power mains and the antenna)

I wasn't sure whether that amp was affected. But when I turned it on the
plate voltage was about half the normal value and the tubes were half as
bright.

What is the best way to troubleshoot and repair an amp that was damaged by
lightning NOT through the antenna BUT through the AC power mains?

What components will likely need to be replaced? Just the caps? What about
the transformer?

Is it worth repairing in the first place?

73's
Rob

Rob wrote:

Recently my tower was hit by lightning. All my ham gear survived except
one. Since I forgot to unplug my Amp Supply LK-500ZB Linear Amp from the AC
power mains, the lightning found a nice way in.. (The rest of my ham gear
was disconnected from the power mains and the antenna)

I wasn't sure whether that amp was affected. But when I turned it on the
plate voltage was about half the normal value and the tubes were half as
bright.

What is the best way to troubleshoot and repair an amp that was damaged by
lightning NOT through the antenna BUT through the AC power mains?

What components will likely need to be replaced? Just the caps? What about
the transformer?

Is it worth repairing in the first place?

73's
Rob

Transformer, diodes, caps are all subject to damage.

I once had a transformer damaged by a nearby strike. I decided to
repair it since it was a multi winding jog that would have been hard
to replace. I unwound and counted turns, measuring the wire size for
each winding. This was an old style transformer with each layer,
neatly flat wound on a fresh layer of paper. Everything looked fine
till I got to the very first turn on the bottom winding.

It had been started sloppily, diagonally, and where it passed under
other turns, the insulation was burned through. This few turn short
lowered the output voltage of all the windings and after a few
seconds, blew the primary fuse.

--
John Popelish

Rob wrote:

Recently my tower was hit by lightning. All my ham gear survived except
one. Since I forgot to unplug my Amp Supply LK-500ZB Linear Amp from the AC
power mains, the lightning found a nice way in.. (The rest of my ham gear
was disconnected from the power mains and the antenna)

I wasn't sure whether that amp was affected. But when I turned it on the
plate voltage was about half the normal value and the tubes were half as
bright.

What is the best way to troubleshoot and repair an amp that was damaged by
lightning NOT through the antenna BUT through the AC power mains?

What components will likely need to be replaced? Just the caps? What about
the transformer?

Is it worth repairing in the first place?

73's
Rob

Transformer, diodes, caps are all subject to damage.

I once had a transformer damaged by a nearby strike. I decided to
repair it since it was a multi winding jog that would have been hard
to replace. I unwound and counted turns, measuring the wire size for
each winding. This was an old style transformer with each layer,
neatly flat wound on a fresh layer of paper. Everything looked fine
till I got to the very first turn on the bottom winding.

It had been started sloppily, diagonally, and where it passed under
other turns, the insulation was burned through. This few turn short
lowered the output voltage of all the windings and after a few
seconds, blew the primary fuse.

--
John Popelish

Rob,

Well, the first thing would be a visual inspection of the top and bottom sides
of the chassis, with the power cord unplugged of course. My guess is that one
or more diodes has opened/shorted. An ohmeter check will confirm that, same
for the electrolytics. Voltage checks of the transformer will tell if it has
obvious damage.

Having said that, it would be best to replace all the diodes and rectifiers and
anything else with physical or electrical problems. My experience with
servicing gear that has taken a lightning strike or severe surge, is that there
are failed and stressed components. Some that were stressed might fail in the
near future. I used to fix TVs that had such misfortune, but after 2-3 repairs
over 6 months, it was obvious that continued repairs were beyond the point of
diminishing returns.

Hope it works out for you.

73s,

Evan

Rob,

Well, the first thing would be a visual inspection of the top and bottom sides
of the chassis, with the power cord unplugged of course. My guess is that one
or more diodes has opened/shorted. An ohmeter check will confirm that, same
for the electrolytics. Voltage checks of the transformer will tell if it has
obvious damage.

Having said that, it would be best to replace all the diodes and rectifiers and
anything else with physical or electrical problems. My experience with
servicing gear that has taken a lightning strike or severe surge, is that there
are failed and stressed components. Some that were stressed might fail in the
near future. I used to fix TVs that had such misfortune, but after 2-3 repairs
over 6 months, it was obvious that continued repairs were beyond the point of
diminishing returns.

Hope it works out for you.

73s,

Evan

wrote:
Rob, you may have answered your question...you say the tubes are HALF
as bright..and the plate voltage is HALF of what its supposed to be?
Does it normally run on 220-240 volts? I suspect a half side open or
damaged pole pig transformer. The amplifier might be fine.....


Thanks for the post. I am using 240 vots to power the amp. (Any self
respecting ham would!)

Yes, I think the transformer may be gone. Like most BIG heavy transformers
for HF amps, it will likely be costly to replace the transformer. But I may
give it a go.

Ca you explain what you mean by a "damaged pole pig transformer". I have
never heard of the term "pole pig"

But after I replace the transformer, I am worried that I may end damaging
the new transformer if another component has failed or is close to failure.
(e.g. a AC Filter cap or diode).
Is this a realistic fear?

Rob

wrote:
Rob, you may have answered your question...you say the tubes are HALF
as bright..and the plate voltage is HALF of what its supposed to be?
Does it normally run on 220-240 volts? I suspect a half side open or
damaged pole pig transformer. The amplifier might be fine.....


Thanks for the post. I am using 240 vots to power the amp. (Any self
respecting ham would!)

Yes, I think the transformer may be gone. Like most BIG heavy transformers
for HF amps, it will likely be costly to replace the transformer. But I may
give it a go.

Ca you explain what you mean by a "damaged pole pig transformer". I have
never heard of the term "pole pig"

But after I replace the transformer, I am worried that I may end damaging
the new transformer if another component has failed or is close to failure.
(e.g. a AC Filter cap or diode).
Is this a realistic fear?

Rob

Hi,

Perhaps he has gas appliances ?

The dryer motor and timer is on 120 but heater element is 240
so his clothes would take longer to dry.

I agree with other post that he could have lost another part in the amp
or the main transformer has a short in the primary.

He could remove the transformer and bench test it using
small ac power supply to input 1-10 volts to the transformer primary
to test is in a safe way.

73 gabe


But if it were the pole transformer don't you think he would have
mentioned that half his lights don't work and that the stove, hot water
heater and dryer aren't working like they used to?

Hi,

Perhaps he has gas appliances ?

The dryer motor and timer is on 120 but heater element is 240
so his clothes would take longer to dry.

I agree with other post that he could have lost another part in the amp
or the main transformer has a short in the primary.

He could remove the transformer and bench test it using
small ac power supply to input 1-10 volts to the transformer primary
to test is in a safe way.

73 gabe


But if it were the pole transformer don't you think he would have
mentioned that half his lights don't work and that the stove, hot water
heater and dryer aren't working like they used to?