Cambridge Audio Azur 640T DAB radio,2006

[N_Cook]

Surprised to see the scematic out there.
Symptom: works for a few minutes then backlight starts dipping out,
exactly every second , no audio out, random letters, (not segments)
disappear from the display and no response to any buttons.
So far found 5V, +\- 15V and are stable but not delved further into the
digital board or other TO220 devices. Corrupted memory? insulated
touching of digital chippery makes no difference.

 

[N_Cook]

On 20/02/2015 14:54, N_Cook wrote:

Surprised to see the scematic out there.
Symptom: works for a few minutes then backlight starts dipping out,
exactly every second , no audio out, random letters, (not segments)
disappear from the display and no response to any buttons.
So far found 5V, +\- 15V and are stable but not delved further into the
digital board or other TO220 devices. Corrupted memory? insulated
touching of digital chippery makes no difference.

schematic for CD and pa , but not 640T for tuner out there, front pic
looked the same at reduced scale.

 

[N_Cook]

4 separate 7805 for some odd reason. 2 non-heasinked ones are stable 5V
but 2 with heatsinks dip to 4.5V or so. Both H/S are perfectly cold and
9.6V ac from Tx is fine. Can only monitor supply side of one of those
7805 and it dips below required, so hopefully it will be failed
smoothing electro, when I get to the other side of the main pcb.

 

[Sjouke Burry]

On 20.02.15 16:49, N_Cook wrote:

4 separate 7805 for some odd reason. 2 non-heasinked ones are stable 5V
but 2 with heatsinks dip to 4.5V or so. Both H/S are perfectly cold and
9.6V ac from Tx is fine. Can only monitor supply side of one of those
7805 and it dips below required, so hopefully it will be failed
smoothing electro, when I get to the other side of the main pcb.

Well, do you like talking/responding to yourself?

 

[Gareth Magennis]

"Sjouke Burry" wrote in message
news:54e76807$0$21155$703f8584@textnews.kpn.nl...

On 20.02.15 16:49, N_Cook wrote:

4 separate 7805 for some odd reason. 2 non-heasinked ones are stable 5V
but 2 with heatsinks dip to 4.5V or so. Both H/S are perfectly cold and
9.6V ac from Tx is fine. Can only monitor supply side of one of those
7805 and it dips below required, so hopefully it will be failed
smoothing electro, when I get to the other side of the main pcb.

Well, do you like talking/responding to yourself?

I think you might find many quiet people listening.



Gareth.

 

[N_Cook]

On 20/02/2015 16:59, Sjouke Burry wrote:

On 20.02.15 16:49, N_Cook wrote:
4 separate 7805 for some odd reason. 2 non-heasinked ones are stable 5V
but 2 with heatsinks dip to 4.5V or so. Both H/S are perfectly cold and
9.6V ac from Tx is fine. Can only monitor supply side of one of those
7805 and it dips below required, so hopefully it will be failed
smoothing electro, when I get to the other side of the main pcb.

Well, do you like talking/responding to yourself?

It means less typing for when I get around to consolidating the threads
and expanding with other obs, for my repair briefs

 

[N_Cook]

electro seemed ok despite 16V,220uF rating on 9V full-wave rectifying,
replaced with 40V 330uF .
Maybe iffy polyswitches, 2 for the one winding. Both marked 30V PG3F,
one measures cold .2R the other .9R, both increasing to double or so
(normal, but should be the same) on touching with a soldering iron, data
not found. Tx has printed rating of 9V , 1A for that sec, so presumably
pg3f is .3A rating rather than 3A,supplying 2x 1amp regulators with
large heatsinks?. Will try monitoring the ac over these polyswitches in
use, perhaps wrong rating polyswitches were used.

 

[N_Cook]

problem not returned in half an hour of use, perhaps was the elctro,
good ESR, good capacity (low volts) presumably at service voltage fails.
The 2 polyswitches, same current, .20V stabilised at .23V after 10
minuts and the other 0.055V to 0.058Vac
I'd not looked on the other side of these polyswitches, has the logo of
a sloping p but 2 gaps in the loop, so a sloping f and a backwards c ,
and 110UF so 1.1 amp ratings presumably. Before an extended test I'll
change the large ohmic one though