TDA4600 / Chopper Transformer

M.Joshi · Joined: 19 Feb 2005 Posts: 2

I am trying to repair a Ferguson T.V (TX100 chassis) which just went dead while switched on.

Initially the standby L.E.D was not coming on but after replacing D15 (BY299) near the chopper transformer, the L.E.D now responds to the remote control however the T.V is still dead.

Is there a way to check if the TDA4600 chip or chopper transformer is dead?

Thanks.

tsgunnell · Joined: 03 Jun 2004 Posts: 49 Location: middx england

i got this from the web dead d15(by299) d28(by299) r711(2k7) so you will need to check d28 and r711 ,d28 is in series with the high tension feed

ausbryant · Guest

As well as the good advice given by last poster, check/replace the Polyester/Mylar Capacitors across both diodes listed, as they can go low value and cause the diodes to then fail.

TX100s also have a nasty habit of suffering intermittent tracking down inside the Focus unit or within the CRT Base connector, which can trip the PSU. The only way to know (safely) is to fit a replacement Focus assembly, if you can still get one, or CRT connector.

Good luck

SHELDONS TV · Joined: 22 Apr 2005 Posts: 25 Location: ENGLAND

WHAT YOU NEED TO DO IS CHECK THE VOLTAGE AT PIN 9 OF YOUR TDA4600(ABOUT 12-13V),IF IT IS LOW OR MISSING CHECK -
C119 FOR OC
R111(100K) FOR OC
D12 FOR OC OR SC
R115(270K)FOR OC-VERY IMPORTANT AS THIS RESISTOR CAN CAUSE PROBLEMS IF IT HAS INCREASED IN VALUE
CHECK C117 FOR OC(100mf)
REPLACE C112(22mf)
REGARDS MIKE

M.Joshi · Joined: 19 Feb 2005 Posts: 2

Thank you for everyone's help with this.

I found the problem to be D28 being incorrectly oriented.

I previously replaced it with a BY229 R800 and the datasheet appears to show the orientation of the anode and cathode different to that of when it was previously connected and working?

The cathode corresponds to the non-banded side on the PCB marking and the anode to black band side of the PCB component marking?

I had de-soldered it to check if it was faulty and soldered it the other way around (Correct according to the datasheet).

Incidently, the BY229 R800 is a good replacement for the D28 however the package style is a TO-220 and you will probably need to create two support wires to solder to the diode.

R711 is 2.7 Ohms. Anything higher will cause the sides of the screen to bow in. I think there is a mistake with the posting (2k7).