Well I had an old student that just got an education in radio shops. He
has an older 172. He took the airplane in for a pitot static check and to
certify a transponder. Spent all day there. First is that they came back
and said he had a blind encoder that was bad, even though he got no
complaints from controllers on the way in.

When he got back in it to fire the airplane up, BOTH radios were also dead.
They quickly looked at it and found a burnt out diode in one on the bench
and the other they kept to check.

All this is HIGHLY unlikely without some help. Then I asked does the
airplane have an external plug for ground power. hmm He said yes. Its an
older 172 with a 12 volt system, but I suspect the shop hooked it up to a 24
volt ground power unit.

Would these symptoms be consistent with a young kid hooking a GPU up at too
high of voltage? Hes learning that many shops you are lucky to get your
airplane back undamage, even if they don't fix what you took it there for.
Thanks in advance.

Mark

Hooking +24 VDC to a +12 VDC system could most definitely cause major damage to
electronic components!

Ron Gardner

mark wrote:

> Well I had an old student that just got an education in radio shops. He
> has an older 172. He took the airplane in for a pitot static check and to
> certify a transponder. Spent all day there. First is that they came back
> and said he had a blind encoder that was bad, even though he got no
> complaints from controllers on the way in.
>
> When he got back in it to fire the airplane up, BOTH radios were also dead.
> They quickly looked at it and found a burnt out diode in one on the bench
> and the other they kept to check.
>
> All this is HIGHLY unlikely without some help. Then I asked does the
> airplane have an external plug for ground power. hmm He said yes. Its an
> older 172 with a 12 volt system, but I suspect the shop hooked it up to a 24
> volt ground power unit.
>
> Would these symptoms be consistent with a young kid hooking a GPU up at too
> high of voltage? Hes learning that many shops you are lucky to get your
> airplane back undamage, even if they don't fix what you took it there for.
> Thanks in advance.
>
> Mark

The question becomes is the damage I described consistent with the likely
damage caused by hooking 24 volts into a 12 volt system?

There seems to be other things that were undamaged. Starter and alternator
appear ok, but then they were not in use when a GPU would be hooked to it.
Doesn't mean they couldn't have been fried anyway, but the last time I
remember this happening it was only radios that were damaged. No idea yet
if the transponder was damaged in anyway yet either.

Aren't airplanes fun LOL
"Ronald Gardner" > wrote in message
...
> Hooking +24 VDC to a +12 VDC system could most definitely cause major
> damage to
> electronic components!
>
> Ron Gardner
>
> mark wrote:
>
>> Well I had an old student that just got an education in radio shops.
>> He
>> has an older 172. He took the airplane in for a pitot static check and
>> to
>> certify a transponder. Spent all day there. First is that they came
>> back
>> and said he had a blind encoder that was bad, even though he got no
>> complaints from controllers on the way in.
>>
>> When he got back in it to fire the airplane up, BOTH radios were also
>> dead.
>> They quickly looked at it and found a burnt out diode in one on the bench
>> and the other they kept to check.
>>
>> All this is HIGHLY unlikely without some help. Then I asked does the
>> airplane have an external plug for ground power. hmm He said yes. Its
>> an
>> older 172 with a 12 volt system, but I suspect the shop hooked it up to a
>> 24
>> volt ground power unit.
>>
>> Would these symptoms be consistent with a young kid hooking a GPU up at
>> too
>> high of voltage? Hes learning that many shops you are lucky to get your
>> airplane back undamage, even if they don't fix what you took it there
>> for.
>> Thanks in advance.
>>
>> Mark
>

A motor Such as a starter will not be affect with this amount of over voltage.
However, electronic components such as diodes, IC's, resistors are another
story. It would depend on the protection built into the radio or GPS or
transponder that would clip the over voltage situation. If it is not there,
then damage most likely will happen. Spent many years in USAF flight simulator
repairing electronics' in just such a situation. The best I ever saw was later
when a fellow worker over voltage a $40,000 X-ray control panel, blew the tops
off every IC!! A bit different though, he dropped a test lead against the DC
trace. The other end was on one leg of a 480 VAC terminal!

Anyway, what you describe is highly probable , a tech not familiar with older 12
VDC systems would out of habit go right to a 24 VDC hook up. With no real
problems going in and multiple failures coming out, the only common factor is
the repair center and what they did! Did you put the repair on a credit card?
If so, call them and dispute the charge and explain what happened, they will
stop payment until resolved! Then at the same time call the repair center and
speak to the top dog only. Tell them what happened and what you suspect the
cause was. If flat refuses to except any of it, tell him you have stopped
payment to him by the card company. And you will take the plane to another
repair center for a check out and verification on your suspicions.

I think if they have any reputation to uphold, he will immediately make a
correction or have an explanation why that could not happen. Take good notes,
then call and ask someone else if what they say is true.

mark wrote:

> The question becomes is the damage I described consistent with the likely
> damage caused by hooking 24 volts into a 12 volt system?
>
> There seems to be other things that were undamaged. Starter and alternator
> appear ok, but then they were not in use when a GPU would be hooked to it.
> Doesn't mean they couldn't have been fried anyway, but the last time I
> remember this happening it was only radios that were damaged. No idea yet
> if the transponder was damaged in anyway yet either.
>
> Aren't airplanes fun LOL
> "Ronald Gardner" > wrote in message
> ...
> > Hooking +24 VDC to a +12 VDC system could most definitely cause major
> > damage to
> > electronic components!
> >
> > Ron Gardner
> >
> > mark wrote:
> >
> >> Well I had an old student that just got an education in radio shops.
> >> He
> >> has an older 172. He took the airplane in for a pitot static check and
> >> to
> >> certify a transponder. Spent all day there. First is that they came
> >> back
> >> and said he had a blind encoder that was bad, even though he got no
> >> complaints from controllers on the way in.
> >>
> >> When he got back in it to fire the airplane up, BOTH radios were also
> >> dead.
> >> They quickly looked at it and found a burnt out diode in one on the bench
> >> and the other they kept to check.
> >>
> >> All this is HIGHLY unlikely without some help. Then I asked does the
> >> airplane have an external plug for ground power. hmm He said yes. Its
> >> an
> >> older 172 with a 12 volt system, but I suspect the shop hooked it up to a
> >> 24
> >> volt ground power unit.
> >>
> >> Would these symptoms be consistent with a young kid hooking a GPU up at
> >> too
> >> high of voltage? Hes learning that many shops you are lucky to get your
> >> airplane back undamage, even if they don't fix what you took it there
> >> for.
> >> Thanks in advance.
> >>
> >> Mark
> >

"Ronald Gardner" > wrote in message
...
>A motor Such as a starter will not be affect with this amount of over
>voltage.
> However, electronic components such as diodes, IC's, resistors are another
> story. It would depend on the protection built into the radio or GPS or
> transponder that would clip the over voltage situation. If it is not
> there,
> then damage most likely will happen.

I completely concur. The most likely thing to blow would be the diodes in
the radio power supply. I too have many years in the military game.
(Retired avionics tech)

Gerry

Spent many years in USAF flight simulator
> repairing electronics' in just such a situation. The best I ever saw was
> later
> when a fellow worker over voltage a $40,000 X-ray control panel, blew the
> tops
> off every IC!! A bit different though, he dropped a test lead against the
> DC
> trace. The other end was on one leg of a 480 VAC terminal!
>
> Anyway, what you describe is highly probable , a tech not familiar with
> older 12
> VDC systems would out of habit go right to a 24 VDC hook up. With no real
> problems going in and multiple failures coming out, the only common factor
> is
> the repair center and what they did! Did you put the repair on a credit
> card?
> If so, call them and dispute the charge and explain what happened, they
> will
> stop payment until resolved! Then at the same time call the repair center
> and
> speak to the top dog only. Tell them what happened and what you suspect
> the
> cause was. If flat refuses to except any of it, tell him you have stopped
> payment to him by the card company. And you will take the plane to
> another
> repair center for a check out and verification on your suspicions.
>
> I think if they have any reputation to uphold, he will immediately make a
> correction or have an explanation why that could not happen. Take good
> notes,
> then call and ask someone else if what they say is true.
>
> mark wrote:
>
>> The question becomes is the damage I described consistent with the likely
>> damage caused by hooking 24 volts into a 12 volt system?
>>
>> There seems to be other things that were undamaged. Starter and
>> alternator
>> appear ok, but then they were not in use when a GPU would be hooked to
>> it.
>> Doesn't mean they couldn't have been fried anyway, but the last time I
>> remember this happening it was only radios that were damaged. No idea
>> yet
>> if the transponder was damaged in anyway yet either.
>>
>> Aren't airplanes fun LOL
>> "Ronald Gardner" > wrote in message
>> ...
>> > Hooking +24 VDC to a +12 VDC system could most definitely cause major
>> > damage to
>> > electronic components!
>> >
>> > Ron Gardner
>> >
>> > mark wrote:
>> >
>> >> Well I had an old student that just got an education in radio shops.
>> >> He
>> >> has an older 172. He took the airplane in for a pitot static check
>> >> and
>> >> to
>> >> certify a transponder. Spent all day there. First is that they came
>> >> back
>> >> and said he had a blind encoder that was bad, even though he got no
>> >> complaints from controllers on the way in.
>> >>
>> >> When he got back in it to fire the airplane up, BOTH radios were also
>> >> dead.
>> >> They quickly looked at it and found a burnt out diode in one on the
>> >> bench
>> >> and the other they kept to check.
>> >>
>> >> All this is HIGHLY unlikely without some help. Then I asked does the
>> >> airplane have an external plug for ground power. hmm He said yes.
>> >> Its
>> >> an
>> >> older 172 with a 12 volt system, but I suspect the shop hooked it up
>> >> to a
>> >> 24
>> >> volt ground power unit.
>> >>
>> >> Would these symptoms be consistent with a young kid hooking a GPU up
>> >> at
>> >> too
>> >> high of voltage? Hes learning that many shops you are lucky to get
>> >> your
>> >> airplane back undamage, even if they don't fix what you took it there
>> >> for.
>> >> Thanks in advance.
>> >>
>> >> Mark
>> >
>

Thanks for the help everyone. It sounds like its totally consistent that
the type of damage that was done was consistent with plugging a 24 volt gpu
with a 12 volt airplane. Thanks again.

"pTooner" > wrote in message
...
>
> "Ronald Gardner" > wrote in message
> ...
>>A motor Such as a starter will not be affect with this amount of over
>>voltage.
>> However, electronic components such as diodes, IC's, resistors are
>> another
>> story. It would depend on the protection built into the radio or GPS or
>> transponder that would clip the over voltage situation. If it is not
>> there,
>> then damage most likely will happen.
>
> I completely concur. The most likely thing to blow would be the diodes
> in the radio power supply. I too have many years in the military game.
> (Retired avionics tech)
>
> Gerry
>
> Spent many years in USAF flight simulator
>> repairing electronics' in just such a situation. The best I ever saw was
>> later
>> when a fellow worker over voltage a $40,000 X-ray control panel, blew the
>> tops
>> off every IC!! A bit different though, he dropped a test lead against
>> the DC
>> trace. The other end was on one leg of a 480 VAC terminal!
>>
>> Anyway, what you describe is highly probable , a tech not familiar with
>> older 12
>> VDC systems would out of habit go right to a 24 VDC hook up. With no real
>> problems going in and multiple failures coming out, the only common
>> factor is
>> the repair center and what they did! Did you put the repair on a credit
>> card?
>> If so, call them and dispute the charge and explain what happened, they
>> will
>> stop payment until resolved! Then at the same time call the repair
>> center and
>> speak to the top dog only. Tell them what happened and what you suspect
>> the
>> cause was. If flat refuses to except any of it, tell him you have
>> stopped
>> payment to him by the card company. And you will take the plane to
>> another
>> repair center for a check out and verification on your suspicions.
>>
>> I think if they have any reputation to uphold, he will immediately make a
>> correction or have an explanation why that could not happen. Take good
>> notes,
>> then call and ask someone else if what they say is true.
>>
>> mark wrote:
>>
>>> The question becomes is the damage I described consistent with the
>>> likely
>>> damage caused by hooking 24 volts into a 12 volt system?
>>>
>>> There seems to be other things that were undamaged. Starter and
>>> alternator
>>> appear ok, but then they were not in use when a GPU would be hooked to
>>> it.
>>> Doesn't mean they couldn't have been fried anyway, but the last time I
>>> remember this happening it was only radios that were damaged. No idea
>>> yet
>>> if the transponder was damaged in anyway yet either.
>>>
>>> Aren't airplanes fun LOL
>>> "Ronald Gardner" > wrote in message
>>> ...
>>> > Hooking +24 VDC to a +12 VDC system could most definitely cause major
>>> > damage to
>>> > electronic components!
>>> >
>>> > Ron Gardner
>>> >
>>> > mark wrote:
>>> >
>>> >> Well I had an old student that just got an education in radio shops.
>>> >> He
>>> >> has an older 172. He took the airplane in for a pitot static check
>>> >> and
>>> >> to
>>> >> certify a transponder. Spent all day there. First is that they came
>>> >> back
>>> >> and said he had a blind encoder that was bad, even though he got no
>>> >> complaints from controllers on the way in.
>>> >>
>>> >> When he got back in it to fire the airplane up, BOTH radios were also
>>> >> dead.
>>> >> They quickly looked at it and found a burnt out diode in one on the
>>> >> bench
>>> >> and the other they kept to check.
>>> >>
>>> >> All this is HIGHLY unlikely without some help. Then I asked does the
>>> >> airplane have an external plug for ground power. hmm He said yes.
>>> >> Its
>>> >> an
>>> >> older 172 with a 12 volt system, but I suspect the shop hooked it up
>>> >> to a
>>> >> 24
>>> >> volt ground power unit.
>>> >>
>>> >> Would these symptoms be consistent with a young kid hooking a GPU up
>>> >> at
>>> >> too
>>> >> high of voltage? Hes learning that many shops you are lucky to get
>>> >> your
>>> >> airplane back undamage, even if they don't fix what you took it there
>>> >> for.
>>> >> Thanks in advance.
>>> >>
>>> >> Mark
>>> >
>>
>
>