Re: Philips GR2.4 TV Chassis

Have a look here:
http://www.hamradio-badarc.co.uk/television/tvp/philipsgr234.htm

http://fileshare.eshop.bg/repair_tips_database/Philips_172.html


Dani.



antispam@xxxxxxxxxxxxx wrote:
Hello Newsgroup

Can anyone make comment to the following fault on a Philips GR2.4
chassis a 29 inch tube model now starting to drive me mad.

Fault symptoms are as follows: HT line low at only 8 volts instead of
nominal 140 volts as per service manual. Chopper transistor tested and
found to be ok on static diode test as did the Line Output Transistor.
Scan coil plug M71 disconnected but power supply voltage still remains
at 8 volts on the main HT line. Then disconnected power supply main HT
line from the Line Output stage and substituted a 100 watt mains Light
bulb as load but still the main HT line stuck at 8 volts. Disconnected
resistor at pin 8 of TDA8385 SOPS chip monitoring over voltage
conditions but still no HT or any set start up. I have the full
service manual but does not contain a circuit description which isn't
helping.

Could anyone make comment as to any further test to be made or
basically explain the power supply start up sequence of this chassis
which uses a TDA8385 S.M.P.S. IC and CNR50 opto-isolator to ultimately
drive the chopper transistor. Incidentally, both latter IC's renewed
together with new chopper and Line Output transistor but still no
results. Alternatively, could anyone direct me to a circuit
description on the Internet as this is absent within the service
manual.

I would be most grateful for any help or comments offered.

Many thanks

Daz

.

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