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Grundig TV CUC1825 does not start

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

--
Bram
...If you want to grow old as a pilot, you have got to know when to push it, 
and when to back off...(Free to Chuck Yeager)
Reply to
Bram Stolk
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Did you change the TDA8145 ? it is certainly dead. Check the capicitors around the yoke and the BY228 diode.

--
--
Marcel Beysselance

marcel.beysselance@hi-tek.fr

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

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

"Marcel Beysselance" schreef >> This Grundig TV set shows the red LED when powered on through its

Reply to
Bram Stolk

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