Crow Berry wrote:
Good Day,

I accidently wrecked my amplified speakers by reversing the polarity
from the battery. It is a fairly inexpensive set from radio shack
with a sub woofer and two small "towers" . I still get a very quiet
sound reproduction as well as a buzz from the speakers, but nothing
from the sub woofer. I took it apart and it has a small circuit
board with a bunch of capacitors, etc on it as well as two amplifier
IC's. I read about someone fixing something like this by replacing
the amplifier chip so I replaced them both........a learning
experience. Anyhow, it made no difference. Now I noticed there is a
zener diode in the circuit right where the power comes in. Could
this get fried by giving it the opposite polarity? Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.
Brett


Yes, the diode is probably shorted, chances are that was there in the
first place to protect against what you did as well as overvoltage. It
likely was the only problem.

Good Day,

I accidently wrecked my amplified speakers by reversing the polarity
from the battery. It is a fairly inexpensive set from radio shack
with a sub woofer and two small "towers" . I still get a very quiet
sound reproduction as well as a buzz from the speakers, but nothing
from the sub woofer. I took it apart and it has a small circuit
board with a bunch of capacitors, etc on it as well as two amplifier
IC's. I read about someone fixing something like this by replacing
the amplifier chip so I replaced them both........a learning
experience. Anyhow, it made no difference. Now I noticed there is a
zener diode in the circuit right where the power comes in. Could
this get fried by giving it the opposite polarity? Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.
Brett

"Crow Berry" wrote in message
...

Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.

First you need a circuit diagram.

Homer J Simpson wrote:
"Crow Berry" wrote in message
...


Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.


First you need a circuit diagram.





Why? I almost never have them for things I repair.

James Sweet wrote:

Homer J Simpson wrote:
"Crow Berry" wrote in message
...


Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.


First you need a circuit diagram.




Why? I almost never have them for things I repair.


Homer works on HVAC.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

On 9 Apr, 06:28, James Sweet wrote:
Homer J Simpson wrote:
"Crow Berry" wrote in message
.. .

Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.

First you need a circuit diagram.

Why? I almost never have them for things I repair.

no way do you need a cct diag to fix a blown zener. Nor indeed for a
large proportion of repairs.


NT

) writes:
On 9 Apr, 06:28, James Sweet wrote:
Homer J Simpson wrote:
"Crow Berry" wrote in message
. ..

Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.

First you need a circuit diagram.

Why? I almost never have them for things I repair.

no way do you need a cct diag to fix a blown zener. Nor indeed for a
large proportion of repairs.

But you have to take into context the original poster and the question.

I read it to mean someone who isn't regularly repairing things, may
not even have much knowledge of electronics. And that at the very least
may require a schematic, if for no other reason than hand-holding.

Think of when you were young and first looked at circuit boards. How
much of it was immdiately obvious?

Michael

Michael Black wrote:

Think of when you were young and first looked at circuit boards.

Circuit boards ?

Graham

Eeyore ) writes:
Michael Black wrote:

Think of when you were young and first looked at circuit boards.

Circuit boards ?

Graham

Now that is funny.

To be fair, I was thinking in terms of a beginner looking at circuit
boards today (since they aren't likely to come across something else).

Nevertheless, it would apply to point to point wiring between tube
sockets, though those had the slight advantage of being easier to
trace.

Michael

Michael A. Terrell wrote:
James Sweet wrote:

Homer J Simpson wrote:

"Crow Berry" wrote in message
...



Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.


First you need a circuit diagram.




Why? I almost never have them for things I repair.



Homer works on HVAC.




So do I, and the same applies. Those are even simpler electrically,
practically every system contains the same basic components wired in the
same way.

"James Sweet" wrote in message
news:7akSh.7522$Cl.6290@trndny08...

First you need a circuit diagram.

Why? I almost never have them for things I repair.

I assume you have experience. You need one or the other and I doubt the OP
has the experience.

"James Sweet" wrote in message
news:JkvSh.13596$Rg2.11731@trndny02...

So do I, and the same applies. Those are even simpler electrically,
practically every system contains the same basic components wired in the
same way.

That doesn't help a beginner. After 50 years you can figure out how 90% of
things work. With 0 years you can figure out how 0% of things work.

James Sweet wrote:

Michael A. Terrell wrote:
James Sweet wrote:

Homer J Simpson wrote:

"Crow Berry" wrote in message
...



Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.


First you need a circuit diagram.




Why? I almost never have them for things I repair.



Homer works on HVAC.



So do I, and the same applies. Those are even simpler electrically,
practically every system contains the same basic components wired in the
same way.


Homer hangs around ABSE and other electronics news groups pretending
that he knows something, but so far has never given anyone any useful
answers. Then he brags that he can't be fired because he's a union HVAC
man. he would need a schematic, because its out of his field.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Eeyore wrote:

Michael Black wrote:

Think of when you were young and first looked at circuit boards.

Circuit boards ?

Graham


Yes, but they had tubes on them. Nasty heat damage to those early
phenolic PC boards by the heat conducted through the pins of the tube
sockets, too.


A little snip from: http://www.americancircuits.com/circuit-board/

We, at American Circuits, are here to fulfill all your printed circuit
board needs. Printed circuit boards were invented in the mid-1930's but
it wasn't until the 1950's, when the auto-assembly process was developed
by the U.S. Army, that printed circuit boards have been a part of
consumer electronics. You can't even begin to imagine how our lives
would be different without the convenience of printed circuit boards,
and printed circuit design has progressed to the point that it makes
them far different than their predecessors.




--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

On 9 Apr, 16:34, (Michael Black) wrote:
) writes:
On 9 Apr, 06:28, James Sweet wrote:
Homer J Simpson wrote:
"Crow Berry" wrote in message
. ..

Any suggestions as
to how to troubleshoot this would be greatly appreciated. I have
already invested more time than the darn thing is worth, but I still
want to try to repair it.

First you need a circuit diagram.

Why? I almost never have them for things I repair.

no way do you need a cct diag to fix a blown zener. Nor indeed for a
large proportion of repairs.

But you have to take into context the original poster and the question.

I read it to mean someone who isn't regularly repairing things, may
not even have much knowledge of electronics. And that at the very least
may require a schematic, if for no other reason than hand-holding.

A cct diag wont help the OP find the zener, and wont help them replace
it. Its not relevant here.


Think of when you were young and first looked at circuit boards. How
much of it was immdiately obvious?

Michael

I remember trying to figure out where the voltage dropped Had me
puzzled for ages that did, meters weren't given to kids like they are
today.

But understanding the workings of the amp is not something the OP need
get into. Anyway modern IC amps really dont explain themselves with
cct diags, theyre just spider structures, a central blob with various
support components hooked on, all of which do things that are well
beyond the absolute beginner.


NT

wrote in message
oups.com...

A cct diag wont help the OP find the zener, and wont help them replace
it. Its not relevant here.

It's highly unlikely there is a zener. Usually there's just a series diode.

"Crow Berry" wrote in message
...
O.K. Thanx for all the responses. The circuit board has a label
" Z 1" where this small glass cylinder is and under it is what looks
like a symbol for a zener diode. Now I am wondering two things - how
do you test a zener diode and how can you tell what value it is for
replacement. The board also has " 4V7" next to the diode symbol and
with a magnifier I can see " C4V7" and "CH" on the diode itself.
Also the glass cylinder sort of looks cracked, but it is hard to tell.
Thanx again, Brett

That is, indeed, a 4.7V Zener diode. Power rating is a guess, but probably in
the neighborhood of 0.5 to 1 watt.
To test a zener, you need a power supply that can supply more voltage than the
zener voltage, at about 10 to 50 ma (DC of course).
Connect a voltmeter directly across the zener.
Connect a 1K resistor between the power supply positive output lead and the
zener cathode.
Connect the power supply negative to the zener anode.
Turn the power supply on and slowly turn the voltage control up. If the
voltmeter reads zero or less than a volt, reverse the zener connections.
If the voltmeter reads in accordance with the power supply's output as it is
adjusted, continue adjusting the power supply voltage upwards until the
voltmeter reads a constant voltage. That reading is the zener voltage.
If the zener is shorted, the voltmeter will read zero or a very low voltage
regardless of the direction in which it is connected.
If it is open, the voltmeter will never stabilize on reading, meaning that the
zener isn't regulating. Of course, this will also happen if the power supply
voltage isn't high enough to make the zener conduct. In that case, get a power
supply capable of higher voltage output.

Cheers!!!
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.

O.K. Thanx for all the responses. The circuit board has a label
" Z 1" where this small glass cylinder is and under it is what looks
like a symbol for a zener diode. Now I am wondering two things - how
do you test a zener diode and how can you tell what value it is for
replacement. The board also has " 4V7" next to the diode symbol and
with a magnifier I can see " C4V7" and "CH" on the diode itself.
Also the glass cylinder sort of looks cracked, but it is hard to tell.
Thanx again, Brett