I was checking a VHF boat radio for power polarity, using my car
battery. Both polarities immediately blew the 10A in-line fuse. I had
the radio sitting on the car and I realized that the heat sink was
touching the sheet metal. The radio had worked before, so I assumed
that it was the heat sink contact which had caused the fuse blows. The
radio now shows a dead short between the input power leads.

Questions:
- could the heat sink contact damage circuitry? I would _think_ that if
the heat sink was connected to anything it would be the power "neutral",
directly, and not through any circuitry. Is it possible that it was
connected through active circuitry?

- if the heat sink contact did cause it, what is the likely extent of
the damage? I.e., would it be worth fixing or is it likely trash? (It
is a Standard Horizon radio - maybe $100 on eBay.)

Thanks,
Bob

BTW - is there a better newsgroup to ask?

Look at the back of the set and locate the large power diode near to the
power input wires.

This usually shorts out.

Desolder a leg off this diode and check it for a short. If it is replace it.

You can run it without this "Reverse Protection Diode" but you will not get
a second chance ever again.

Other than that, I don't know


PS Where can I buy Static Cleaner ??

Edward B Tweedel
Oxford
UK

This is absolutely correct advice.....
.... and as advised if the reverse polarity diode is shorted...... replace it
immediately..... do use the radio without it.
Certainly other parts could be faulty due to the shorted heatsink, but this
is a good place to start.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
----------------------------------------

snipperoo:
"Fast Eddy" wrote in message
Look at the back of the set and locate the large power diode near to the
power input wires.
This usually shorts out.
Desolder a leg off this diode and check it for a short. If it is replace
it.
You can run it without this "Reverse Protection Diode" but you will not
get
a second chance ever again.

Ummm "do use the radio" ??? :-)
You have the same finger problem I am afflicted with !!


--
Regards ............... Rheilly Phoull

"Sofie" wrote in message
...
This is absolutely correct advice.....
... and as advised if the reverse polarity diode is shorted...... replace
it
immediately..... do use the radio without it.
Certainly other parts could be faulty due to the shorted heatsink, but
this
is a good place to start.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
----------------------------------------

snipperoo:
"Fast Eddy" wrote in message
Look at the back of the set and locate the large power diode near to the
power input wires.
This usually shorts out.
Desolder a leg off this diode and check it for a short. If it is replace
it.
You can run it without this "Reverse Protection Diode" but you will not
get
a second chance ever again.

Fast Eddy wrote:

Look at the back of the set and locate the large power diode near to the
power input wires.

This usually shorts out.
...

That was it! Replaced it and it works! Thanks a million, as they used
to say. I love newsgroups. Bob