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Turn on after 3 seconds turn off

D

donskister

Jan 1, 1970
0
I went to my friend he ask for my help if i can repair his kenwood
model RX-39 audio system. I turn on the power then it seems the unit
have no problem but after 3 seconds the unit turn off and the message
appear on the display ( Protect )..I noticed after repeatedly turn on i
hear a clicking sound inside the unit before the unit turn off..I plan
to open it by next week so that i can first gather informations before
i try to repair it.

By the way... My friend told me that sometimes he can used the unit
for a couple of months when he will not used the unit for a weeks then
after the unit will fail again then he will not used the unit for a
weeks..... it seems that the unit is working if had taken a rest.
 
J

James Sweet

Jan 1, 1970
0
donskister said:
I went to my friend he ask for my help if i can repair his kenwood
model RX-39 audio system. I turn on the power then it seems the unit
have no problem but after 3 seconds the unit turn off and the message
appear on the display ( Protect )..I noticed after repeatedly turn on i
hear a clicking sound inside the unit before the unit turn off..I plan
to open it by next week so that i can first gather informations before
i try to repair it.

By the way... My friend told me that sometimes he can used the unit
for a couple of months when he will not used the unit for a weeks then
after the unit will fail again then he will not used the unit for a
weeks..... it seems that the unit is working if had taken a rest.


It could be a cracked solder joint, you have to be careful working on
audio amps, sometimes the protection circuit will save them, sometimes
they suffer a catastrophic failure and then you're looking at new output
transistors and a whole pile of parts they take out when they blow.
 
B

budgie

Jan 1, 1970
0
I went to my friend he ask for my help if i can repair his kenwood
model RX-39 audio system. I turn on the power then it seems the unit
have no problem but after 3 seconds the unit turn off and the message
appear on the display ( Protect )..I noticed after repeatedly turn on i
hear a clicking sound inside the unit before the unit turn off..I plan
to open it by next week so that i can first gather informations before
i try to repair it.

By the way... My friend told me that sometimes he can used the unit
for a couple of months when he will not used the unit for a weeks then
after the unit will fail again then he will not used the unit for a
weeks..... it seems that the unit is working if had taken a rest.

I'd suspect a speaker load problem.
 
M

Morse

Jan 1, 1970
0
donskister said:
I went to my friend he ask for my help if i can repair his kenwood
model RX-39 audio system. I turn on the power then it seems the unit
have no problem but after 3 seconds the unit turn off and the message
appear on the display ( Protect )..I noticed after repeatedly turn on i
hear a clicking sound inside the unit before the unit turn off..I plan
to open it by next week so that i can first gather informations before
i try to repair it.

By the way... My friend told me that sometimes he can used the unit
for a couple of months when he will not used the unit for a weeks then
after the unit will fail again then he will not used the unit for a
weeks..... it seems that the unit is working if had taken a rest.

My guess would be failing capacitors causing DC leakage and upset bias in
the audio path or something similar.

It needs attention as using it in this condition and repeatedly trying to
power it on could cause expensive damage.

Morse.
 
A

Arfa Daily

Jan 1, 1970
0
Morse said:
My guess would be failing capacitors causing DC leakage and upset bias in
the audio path or something similar.

It needs attention as using it in this condition and repeatedly trying to
power it on could cause expensive damage.

Morse.
Some of the old Kenwoods used to have trouble with the delay cap in the
protect circuit, leaking. As the problem is intermittent, might be worth a
look, but otherwise, as others have said, good first place to look is at the
speakers and their wiring.

Arfa
 
D

donskister

Jan 1, 1970
0
Thanks guys for your advised il be visiting my friend house this week
to check it again...i will post immediately what happen when i check
it.. i hope you help me guys till the end to repair my friend
equipment ....thanks in advance
 
Some of the old Kenwoods used to have trouble with the delay cap in the
protect circuit, leaking. As the problem is intermittent, might be worth a
look, but otherwise, as others have said, good first place to look is at the
speakers and their wiring.

Arfa
I'd go with the delay cap too. Isn't that typically a low value
electrolytic in the relay turn on circuitry?
Jango.
 
A

Arfa Daily

Jan 1, 1970
0
I'd go with the delay cap too. Isn't that typically a low value
electrolytic in the relay turn on circuitry?
Jango.

It is. I've had more than a few over the years.

Arfa
 
M

Morse

Jan 1, 1970
0
Arfa Daily said:
Some of the old Kenwoods used to have trouble with the delay cap in the
protect circuit, leaking. As the problem is intermittent, might be worth a
look, but otherwise, as others have said, good first place to look is at
the speakers and their wiring.

Arfa


I wonder if the correct impedance speakers are being used? It's not that
uncommon for people to think it's OK to just bung any old speakers onto an
amp, and end up with 4 Ohm speakers on an 8 Ohm system, causing shutdowns.

The OP said the system works after 'taking a rest', which is why I suggested
an amp fault. A lot of amps will shut down when there is DC present on the
speaker terminals, even though the sound may appear normal.. I'd expect most
people not cursed with cloth ears to pick up on faulty speakers or wiring-
the sound would be low, distorted or non-existent. Mind, I've seen
situations where people were totally unaware of a dead audio channel so
anything's possible!

Morse
 
A

Arfa Daily

Jan 1, 1970
0
Morse said:
I wonder if the correct impedance speakers are being used? It's not that
uncommon for people to think it's OK to just bung any old speakers onto an
amp, and end up with 4 Ohm speakers on an 8 Ohm system, causing shutdowns.

The OP said the system works after 'taking a rest', which is why I
suggested an amp fault. A lot of amps will shut down when there is DC
present on the speaker terminals, even though the sound may appear
normal.. I'd expect most people not cursed with cloth ears to pick up on
faulty speakers or wiring- the sound would be low, distorted or
non-existent. Mind, I've seen situations where people were totally unaware
of a dead audio channel so anything's possible!

Morse

A couple of years back, I had a speaker that supposedly caused an amp to
shut down intermittently, and particularly on one specific piece of music,
which the customer obligingly supplied. I was of course sceptical, but the
owner insisted that he had proved beyond doubt, that it was the speaker.
When I tried the system out, both speakers sounded fine on the music I was
playing, but when I put on his offering, the system immediately started to
intermittently shut down. The cause finally turned out to be bass-related,
but not for any conventional speaker fault that you would hear on any old
passage of music, or even if you turned it up loud. It was actually due to
one of the braided flexible tails that go between the cone and the
connection tag board. A number of the strands had fractured at one end
through metal fatigue, and had come unravelled. This left them flying around
in mid air. On most music, and at most drive levels, this was of no
noticeable consequence. However, on the offending piece of music, on certain
bass passages, some kind of resonance was hit, and the free strands flew
about like things possessed, and intermittently touched the other tail,
resulting in a momentary short across the amp, which then caused its
protection circuit to shut it down for a few seconds.

So whilst I absolutely agree that normally, defective speakers or wiring
would be easily heard, it's not always the case ... ;-)

Arfa
 
B

budgie

Jan 1, 1970
0
A couple of years back, I had a speaker that supposedly caused an amp to
shut down intermittently, and particularly on one specific piece of music,
which the customer obligingly supplied. I was of course sceptical, but the
owner insisted that he had proved beyond doubt, that it was the speaker.
When I tried the system out, both speakers sounded fine on the music I was
playing, but when I put on his offering, the system immediately started to
intermittently shut down. The cause finally turned out to be bass-related,
but not for any conventional speaker fault that you would hear on any old
passage of music, or even if you turned it up loud. It was actually due to
one of the braided flexible tails that go between the cone and the
connection tag board. A number of the strands had fractured at one end
through metal fatigue, and had come unravelled. This left them flying around
in mid air. On most music, and at most drive levels, this was of no
noticeable consequence. However, on the offending piece of music, on certain
bass passages, some kind of resonance was hit, and the free strands flew
about like things possessed, and intermittently touched the other tail,
resulting in a momentary short across the amp, which then caused its
protection circuit to shut it down for a few seconds.

So whilst I absolutely agree that normally, defective speakers or wiring
would be easily heard, it's not always the case ... ;-)

Oddly enough, I had a shutdown/incompatiblity issue about 20 years back, with an
Akai amp driving Mission 700 speakers. The Akai spec was "minimum 4 ohms".

The 700's sounded fine in the showroom, and could be driven hard by their amp.
At home, anything above modest level with certain material caused the amp
protection to intervene. Eventually got the impedance curves for the 700's and
found there was one sub-1khz area where the impedance dropped to ~2.5 ohm.
Tests with a signal source proved the susceptibilty, and the Missions were
returned.
 
D

donskister

Jan 1, 1970
0
Hi Guys...

I just came to my friend place yesterday to repair his audio system
with full of knowledge thru the tips I gathered to all of you guys (
Checked for cracked solder joint, speaker wiring, failing capacitors in
the protect circuit... I confirmed that when I checked his audio before
theres no speakers connected so I plug the cord on the outlet and turn
it on again same as before the unit shut off after 2 to 3 sec, I
cleaned the connector by tipping using my finger to cleaned the
connector outlet before we connect the speakers on the unit then we
turn it on the unit does not shut off so we play a cd to test its
working! But we noticed that when we turn up the volume the unit shut
off( protect) so we try it again to know what level of volume the unit
shut off its seems that the unit seems working if only set below 35 (
note. Max volume 60 ). After that we dismantle the unit to check the
components of power supply hoping to find fail components by visual
check up then and again slap a little the connector pin of the speaker
to cleaned hoping to remove the one that causing the shut off if any .
After we assemble the unit we connect the speakers and turn it on its
working so we decide to turn up the volume above 35 the does not shut
so we adjust it to 40,45 and 50 the unit does not shut off. Im happy
that I successfully fixed his unit. But Im confused what really the
caused why that unit behave like that?????? and How I repaired that ,I
only disassemble the unit?????

Don
 
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