Grundig TV CUC1825 does not start

[Bram Stolk]

This Grundig TV set shows the red LED when powered on through its
mainswitch. At a 1Hz rate one can tell that the supply is trying to do
something. Commanding the set thru the REMCO does not work either.

I removed its chassis and tried to diagnose the problem.
With the deflection yoke connector (J5-J6)removed and a 60 watt ballast lamp
connected to the A+ the light comes on for about a second when Prog + on
Front Panel is pressed. (Pressing Prog - does not !)

The H+ 5 Volt is steady and always present.
I have removed and replaced the obvious ? parts: TDA 4605-3, 2 Opto couplers
CN17F1, FET T6006 PC50, checked the Caps and A+ 140 Volt ckts for ESR and
shorts.

Opening the fuse S161026 = disabling the +D, +M, +B voltages turns the light
continuously ON, so I suspected a short/load in that ckt. It all measured OK
showing MegOhms. I reconnected the fuse.

Opening the fuse S161036 = disabling the +E, +F, voltages turns the light
continuously ON, so I suspected a short/load in that ckt. It all measured OK
showing MegOhms. I reconnected the fuse.

A visual learned that R55014 = 4,7 Ohm at pin 5 of TDA8145 E/W Correction
Ckt was exploded, replacement did not result into normal ops.

Is there anyone who can help me to pinpoint the problem ??

Thanks all

 

[Marcel Beysselance]

This Grundig TV set shows the red LED when powered on through its
mainswitch. At a 1Hz rate one can tell that the supply is trying to do
something. Commanding the set thru the REMCO does not work either.

I removed its chassis and tried to diagnose the problem.
With the deflection yoke connector (J5-J6)removed and a 60 watt ballast lamp
connected to the A+ the light comes on for about a second when Prog + on
Front Panel is pressed. (Pressing Prog - does not !)

The H+ 5 Volt is steady and always present.
I have removed and replaced the obvious ? parts: TDA 4605-3, 2 Opto couplers
CN17F1, FET T6006 PC50, checked the Caps and A+ 140 Volt ckts for ESR and
shorts.

Opening the fuse S161026 = disabling the +D, +M, +B voltages turns the light
continuously ON, so I suspected a short/load in that ckt. It all measured OK
showing MegOhms. I reconnected the fuse.

Opening the fuse S161036 = disabling the +E, +F, voltages turns the light
continuously ON, so I suspected a short/load in that ckt. It all measured OK
showing MegOhms. I reconnected the fuse.

A visual learned that R55014 = 4,7 Ohm at pin 5 of TDA8145 E/W Correction
Ckt was exploded, replacement did not result into normal ops.

Is there anyone who can help me to pinpoint the problem ??

Thanks all

Did you change the TDA8145 ? it is certainly dead.
Check the capicitors around the yoke and the BY228 diode.


--
--
Marcel Beysselance

[email protected]

www.hi-tek.fr
Boutique en ligne
5 millions de références TV Ménager Froid

 

[Bram Stolk]

Dear Marcel,
I replaced the TDA8145, and found BY229 beyond suspicion, no changes to
operation of the CUC1825

I did receive another comment that one cannot test the CUC1825 primary
powersupply using the lamptest method. (In German)
......Leider wird es immer schwieriger ein Netzteil auf korrekte Funktion zu
überprüfen. Neuere Gerät werden mit immer mehr Schutzschaltungen
ausgestattet, die es nahezu unmöglich machen, das Netzteil seperat zu
testen. Zu diesen Geräten gehört zum Beispiel das Chassis CUC1825 und
CUC1826 von Grundig. .....

Can you comment on that ?, is it really impossible to test the Prim PS with
a disabled HOT ckt ?

I continued to use my ballastlamp approach and found out that the Prim PS
does not shut-off due to heavy loading in the ckts protected by fuse
S161026, Connecting an external 9 VDC PS at the opened fuse, triggers the
protection circuit and cuts the 140 VDC to my ballast lamp. I am now tracing
SS, SBY and RESET signals generating from UP's and SMD ckts...driving me
crazy.

I am sure Grundig has a more simple approach by just removing and replacing
UProcessors and Feature Box ?
BTW will Powersupply ckts continue to function if I physically remove the
Feature Box ?


Thanks
Bram