Hi,
This unit failed to power up. Removed case and found the internal 1amp slow blow fuse (T1AL) was shot. replaced fuse turned power on power to unit successful as unit goes into standby mode red light on front and clock displayed.
As soon as the unit is turned on proper the Fuse blows again.
I am a novice at this sort of thing but did some rudimentary checking on the board that the transformer is attached to looking for blown capacitors or a short of some kind, can anyone suggest a way forward. I am thinking it cannot be that much wrong with it as initail power up is ok?
I would rather attempt a repair than put it into a shop as the cost of repair would probaly outweigh the value of the unit. any help? suggestions?

Cheers
Billy

Billy Brainstorm wrote in message
...
Hi,
This unit failed to power up. Removed case and found the internal 1amp
slow blow fuse (T1AL) was shot. replaced fuse turned power on power to unit
successful as unit goes into standby mode red light on front and clock
displayed.
As soon as the unit is turned on proper the Fuse blows again.
I am a novice at this sort of thing but did some rudimentary checking on the
board that the transformer is attached to looking for blown capacitors or a
short of some kind, can anyone suggest a way forward. I am thinking it
cannot be that much wrong with it as initail power up is ok?
I would rather attempt a repair than put it into a shop as the cost of
repair would probaly outweigh the value of the unit. any help? suggestions?

Cheers
Billy

++++++
Checked the speaker wiring ?
What is the output device/s ?

On Tuesday, September 11, 2012 8:58:51 AM UTC+1, N_Cook wrote:
Billy Brainstorm wrote in message ... Hi, This unit failed to power up. Removed case and found the internal 1amp slow blow fuse (T1AL) was shot. replaced fuse turned power on power to unit successful as unit goes into standby mode red light on front and clock displayed. As soon as the unit is turned on proper the Fuse blows again. I am a novice at this sort of thing but did some rudimentary checking on the board that the transformer is attached to looking for blown capacitors or a short of some kind, can anyone suggest a way forward. I am thinking it cannot be that much wrong with it as initail power up is ok? I would rather attempt a repair than put it into a shop as the cost of repair would probaly outweigh the value of the unit. any help? suggestions? Cheers Billy ++++++ Checked the speaker wiring ? What is the output device/s ?

didn't have the speakers connected.
heres a link to give you an idea of the unit in question
http://www.jvc.co.uk/files/instructi...t0105-008a.pdf

"Billy Brainstorm" wrote in message
...
Hi,
This unit failed to power up. Removed case and found the internal 1amp
slow blow fuse (T1AL) was shot. replaced fuse turned power on power to
unit successful as unit goes into standby mode red light on front and
clock displayed.
As soon as the unit is turned on proper the Fuse blows again.
I am a novice at this sort of thing but did some rudimentary checking on
the board that the transformer is attached to looking for blown capacitors
or a short of some kind, can anyone suggest a way forward. I am thinking
it cannot be that much wrong with it as initail power up is ok?

Oh how I wish I had a quid for every time that I've heard that. It's a bit
like saying that you have a pain in the chest, but you're sure it can't be
much because you've had pains in your arms or legs before, and they haven't
been anything serious ...



Chances are that in standby, very little other than the system control micro
is actually powered. When you attempt to take it out of standby, that's when
the main rails to (for instance) the output stages will come up. Any short
across any of the main rails, will likely take the fuse out. By far the most
common reason for such a short to be present, is failed output devices.
these might be in the form of discrete transistors, or integrated into a car
radio-type output IC, or an STK output hybrid. Without schematics, you may
not find that you can progress very far, given your admitted lack of
experience ...



I would rather attempt a repair than put it into a shop as the cost of
repair would probaly outweigh the value of the unit. any help?
suggestions?

Cheers
Billy


Hmmmm ... d:-\ }=

Arfa

thanks for the reply
have taken unit apart to investigate further cannot see any obvious short
the small board seems basic (says i the novice so please excuse my ignorance )

i will try and post a few pictures if it may help maybe the sages on this site can nurse me through a little more investigation?

"Billy Brainstorm" wrote in message
...
i will try and post a few pictures if it may help maybe the sages on this
site can nurse me through a little more investigation?


It's not really a 'site' as such. It's a usenet newsgroup that is being
fronted by the Google Groups site that you are accessing from. You probably
won't be able to post pictures direct. Most people post a link to something
like Photo Bucket, where they place the pictures.

Arfa

On Wednesday, 12 September 2012 01:22:12 UTC+1, Arfa Daily wrote:
"Billy Brainstorm" wrote in message ... i will try and post a few pictures if it may help maybe the sages on this site can nurse me through a little more investigation? It's not really a 'site' as such. It's a usenet newsgroup that is being fronted by the Google Groups site that you are accessing from. You probably won't be able to post pictures direct. Most people post a link to something like Photo Bucket, where they place the pictures. Arfa

links to pictures....
http://i1148.photobucket.com/albums/...d/a420684f.jpg
http://i1148.photobucket.com/albums/...d/e039b327.jpg
http://i1148.photobucket.com/albums/...d/d667ae55.jpg

thanks for looking... the blown fuse is in top left of the board mains input goes into the socket near it.
tips on how to try and trace the fault would be good, is the board relatively simple?

Cheers Billy

"Billy Brainstorm" wrote in message
...
On Wednesday, 12 September 2012 01:22:12 UTC+1, Arfa Daily wrote:
"Billy Brainstorm" wrote in message
... i will
try and post a few pictures if it may help maybe the sages on this site
can nurse me through a little more investigation? It's not really a
'site' as such. It's a usenet newsgroup that is being fronted by the
Google Groups site that you are accessing from. You probably won't be
able to post pictures direct. Most people post a link to something like
Photo Bucket, where they place the pictures. Arfa

links to pictures....
http://i1148.photobucket.com/albums/...d/a420684f.jpg
http://i1148.photobucket.com/albums/...d/e039b327.jpg
http://i1148.photobucket.com/albums/...d/d667ae55.jpg

thanks for looking... the blown fuse is in top left of the board mains
input goes into the socket near it.
tips on how to try and trace the fault would be good, is the board
relatively simple?

Cheers Billy




Billy, those photobucket links don't seem to work.


Gareth.

On Wednesday, 12 September 2012 08:40:28 UTC+1, Gareth Magennis wrote:
"Billy Brainstorm" wrote in message ... On Wednesday, 12 September 2012 01:22:12 UTC+1, Arfa Daily wrote: "Billy Brainstorm" wrote in message ... i will try and post a few pictures if it may help maybe the sages on this site can nurse me through a little more investigation? It's not really a 'site' as such. It's a usenet newsgroup that is being fronted by the Google Groups site that you are accessing from. You probably won't be able to post pictures direct. Most people post a link to something like Photo Bucket, where they place the pictures. Arfa links to pictures.... http://i1148.photobucket.com/albums/...d/a420684f.jpg http://i1148.photobucket.com/albums/...d/e039b327.jpg http://i1148.photobucket.com/albums/...d/d667ae55.jpg thanks for looking... the blown fuse is in top left of the board mains input goes into the socket near it. tips on how to try and trace the fault would be good, is the board relatively simple? Cheers Billy Billy, those photobucket links don't seem to work. Gareth.

http://s1148.beta.photobucket.com/us...7ae55.jpg.html
http://s1148.beta.photobucket.com/us...9b327.jpg.html
http://s1148.beta.photobucket.com/us...0684f.jpg.html

re try of the photo links!

"Billy Brainstorm" wrote in message
...
On Wednesday, 12 September 2012 08:40:28 UTC+1, Gareth Magennis wrote:
"Billy Brainstorm" wrote in message
... On
Wednesday, 12 September 2012 01:22:12 UTC+1, Arfa Daily wrote: "Billy
Brainstorm" wrote in message
... i will
try and post a few pictures if it may help maybe the sages on this site
can nurse me through a little more investigation? It's not really a
'site' as such. It's a usenet newsgroup that is being fronted by the
Google Groups site that you are accessing from. You probably won't be
able to post pictures direct. Most people post a link to something
like Photo Bucket, where they place the pictures. Arfa links to
pictures....
http://i1148.photobucket.com/albums/...d/a420684f.jpg
http://i1148.photobucket.com/albums/...d/e039b327.jpg
http://i1148.photobucket.com/albums/...d/d667ae55.jpg
thanks for looking... the blown fuse is in top left of the board mains
input goes into the socket near it. tips on how to try and trace the
fault would be good, is the board relatively simple? Cheers Billy
Billy, those photobucket links don't seem to work. Gareth.

http://s1148.beta.photobucket.com/us...7ae55.jpg.html
http://s1148.beta.photobucket.com/us...9b327.jpg.html
http://s1148.beta.photobucket.com/us...0684f.jpg.html

re try of the photo links!


As far as I can see, there are one and a half completely independent power
supplies on that board. The standby supply is based around the small
transformer in the middle of the board. This is what powers all the system
control circuitry on the unit's front panel. The main power supply comprises
the big transformer at the edge of the board, the four large diodes at the
edge of the board, and the relay by the side of the little transformer. This
is the 'half' power supply, because there is no additional circuitry on that
board which would make it a 'whole' power supply e.g. a pair of main
smoothing caps. I would guess that the rest of the supply is on the power
amp board.

Looking at the print, the fuse that's blowing feeds the primary of the big
transformer via the relay contacts, as well as the small standby transformer
from before the relay contacts. So the sequence of events is that with a
good fuse in place, the small transformer is fed, and that piece of
circuitry then produces a standby rail - probably 5 or 12 volts - that is
fed out to the system control micro at the front panel. When you attempt to
turn on from standby, the system control micro asserts the power control
line that's fed back to the power supply, and this line pulls the relay to
apply mains power to the primary of the big transformer. And that's when it
all goes tits up and the fuse blows. The other fuse on the board between the
big transformer and the four large diodes, is connected into the secondary
side of the transformer, and presumably that one never blows ?

Looking at the primary-side fuse that has blown, it appears to be quite
blackened inside. You can tell a lot about what caused a fuse to blow by
looking at what's left afterwards. If the wire is just separated with no
'blobs' on the broken ends, or there is just a tiny little "phtt" on the
inside of the glass, chances are it's a random 'tired fuse' failure, caused
by metal fatigue from the fuse wire stretching at every turn on. If the fuse
shows clear signs of melting without much if any kind of 'blast' mark inside
the glass, then it has blown because of a downstream overload such as a
faulty output stage.

However, when a fuse is blackened inside, it usually means that it has blown
as a result of a serious short almost on top of it ...

That doesn't bode well for you getting a fix on this. Apart from the
transformer primary itself, about the only other component that I can see
across the mains, is the blue VDR next to the relay. Whilst these do fail,
usually they show physical signs that they have.

About the only other checks that I can suggest that you try at a 'basic'
level is to remove the VDR (it doesn't need it to work), remove the
secondary side fuse, replace the primary side fuse, and try again. If the
fuse immediately blows again, then there's a good chance that the big
transformer has a shorted primary winding. It's not super common, but by no
means unknown, either. I would guess that I probably change on average two
or three transformers a year for having a shorted primary.

Arfa

On Tuesday, 11 September 2012 08:47:13 UTC+1, Billy Brainstorm wrote:
Hi, This unit failed to power up. Removed case and found the internal 1amp slow blow fuse (T1AL) was shot. replaced fuse turned power on power to unit successful as unit goes into standby mode red light on front and clock displayed. As soon as the unit is turned on proper the Fuse blows again. I am a novice at this sort of thing but did some rudimentary checking on the board that the transformer is attached to looking for blown capacitors or a short of some kind, can anyone suggest a way forward. I am thinking it cannot be that much wrong with it as initail power up is ok? I would rather attempt a repair than put it into a shop as the cost of repair would probaly outweigh the value of the unit. any help? suggestions? Cheers Billy

Thanks for your help and the pointers re the fuse.
I havent had time to look again but will over the weekend, looking like a replacement transformer But probably not worth the cost.
Thanks you very much for your help.
You never know i may have something else thrown at me to fix and i may ask for more help in the future.
take care

Cheers
Billy

On Wed, 12 Sep 2012 01:13:05 -0700 (PDT), Billy Brainstorm
put finger to keyboard and composed:

Direct links to your photos ...
http://i1148.photobucket.com/albums/...d/d667ae55.jpg
http://i1148.photobucket.com/albums/...d/e039b327.jpg
http://i1148.photobucket.com/albums/...d/a420684f.jpg

Page 8 of the following UX-P5 circuit diagrams looks very much like
your power supply board. The P/N of the main transformer is the same
in any case.
http://www.go-gddq.com/upload/2009_0...1710066960.pdf

UX-P5 Service Manual:
http://www.go-gddq.com/upload/2009_0...1710075498.pdf

The following link looked promising, but it has expired:
http://jvckenwood.com.au/jvcfiles/UX-P7%23SCH1.pdf

Here is another service manual, but it looks quite a bit different:
http://service.eclubthai.com/new/audio/JVC/UX-P550U.pdf

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

"Franc Zabkar" wrote in message
...
On Wed, 12 Sep 2012 01:13:05 -0700 (PDT), Billy Brainstorm
put finger to keyboard and composed:

Direct links to your photos ...
http://i1148.photobucket.com/albums/...d/d667ae55.jpg
http://i1148.photobucket.com/albums/...d/e039b327.jpg
http://i1148.photobucket.com/albums/...d/a420684f.jpg

Page 8 of the following UX-P5 circuit diagrams looks very much like
your power supply board. The P/N of the main transformer is the same
in any case.
http://www.go-gddq.com/upload/2009_0...1710066960.pdf

UX-P5 Service Manual:
http://www.go-gddq.com/upload/2009_0...1710075498.pdf

The following link looked promising, but it has expired:
http://jvckenwood.com.au/jvcfiles/UX-P7%23SCH1.pdf

Here is another service manual, but it looks quite a bit different:
http://service.eclubthai.com/new/audio/JVC/UX-P550U.pdf

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


Looking at the PSU schematics, it's *just* possible that one of the VH
reccies - that's D1004 to D1007 - might take out the primary side fuse if
it was short circuit. That said, the fuse did look very violently blown in
the picture. Still, Billy, I guess before condemning the transformer, it
would be worth just checking those diodes with an ohm meter, and the wires
to points 1, 2, 3 & 4, 5, 6 disconnected.

Arfa