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27th Jun 2022, 7:00 pm | #1 |
Moderator
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Location: Wembley, Middlesex
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Philips CTX chassis
This was brought to me by another member.
It is a non remote model. It appears dead. On switching on there is 330V going to the base of the chopper transistor T7355 but nothing on the emitter. The Line O/P transistor is Ok, and disconnecting it makes no difference. There is only 20V instead of 100V at the collector of the driver transistor T7353. There is 6.8V on the emitter, and 7.5V on the base, (which should be 6.6V) so its unlikely the driver is faulty. I have checked D6360 and it appears OK. I haven’t put a scope on it but it appears that the power supply is not oscillating. I may not be able to repair the set as the owner lives quite same way from me but I would like to know what might be causing this fault so that e could come back to it. Last edited by Michael Maurice; 27th Jun 2022 at 7:06 pm. Reason: addition of a diagram |
27th Jun 2022, 7:29 pm | #2 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
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Re: Philips CTX chassis
The first thing I always used to do with this chassis is resolder the line output transformer’s pins. All sorts of logic-defying faults would vanish.
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27th Jun 2022, 8:00 pm | #3 |
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Join Date: Feb 2006
Location: Wembley, Middlesex
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Re: Philips CTX chassis
First thing I did Nick. I’ve serviced many of these sets in the day.
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27th Jun 2022, 8:07 pm | #4 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
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Re: Philips CTX chassis
Sorry!
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27th Jun 2022, 9:30 pm | #5 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,550
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Re: Philips CTX chassis
It seems like 100 years ago since I last repaired one of these! I think the drive for the power supply comes from the line driver chip. From memory ..... TDA (posssibly TBA) 2577B?? Long since got rid of everything for these....
Is that snip the right circuit in post #1? I don't remember these having E-W correction circuits and I see mention of it over on the RH side of the circuit. It's also worth checking the two protection transistors (connected as a thyristor) T7330 and T7331. One or both failing will stop the power supply.
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27th Jun 2022, 9:34 pm | #6 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Philips CTX chassis
In the January 1993 issue of Television magazine, one of the reported faults in "TV Fault Finding" page 184, describes very similar conditions. The low voltage at the collector of the chopper drive transistor, TR7353 was due to C2395 (100uF) being s/c.
Hope this may be helpful. Regards, Symon |
27th Jun 2022, 9:44 pm | #7 |
Heptode
Join Date: Jan 2007
Location: Luton, Bedfordshire, UK.
Posts: 891
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Re: Philips CTX chassis
Fault list for CTX and related for easy reference:
Philips CTNBB No pic - OSD OK replace s/m transistor 7651 (1F/2 npn) .Read O.K. Philips CTO/CTX To reset settings With set sw'd on s/c the left hand side of R3017 to the bottom of R3014 Philips CTX Dead R3394 R3395 OC 27k 2.5W Philips CTX Dead crack in print at corner of remote psu Philips CTX Dead R3298 4R7 dropper o/c Philips CTX Dead - buzzing from psu & spkr HT ok - IC7375 TDA2577 u/s Philips CTX Dead - HT low at 50v Trs7322 & 7323 BC548 & BC558 faulty - (read ok) Philips CTX Dead - no 125v, faint whine from psu D6317 1N4148 leaky Philips CTX Dead - overload on LOP EHT lead s/c Philips CTX DEAD SET SCREAMS AND BLOWS LINE OP TRANSISTOR IF L C2351 CHOPPER TRANSISTOR BASE COUPLER 4u7 Philips CTX Dead with whistle - ok on dummy load Dry joints C2609 Philips CTX Dead. Check R3394/3395 27k , 2.5W for o/c. Philips CTX EHT & CRT heaters ok but no raster & loud hum fro R3585 ( 2R2 ) o/c Philips CTX Frame - picture Jitter. Drys around LOPTX Philips CTX Frame collapse - Intermittent. Check connections around LOPTX Philips CTX Int colour TDA3560 Philips CTX Int dead Dry joints LOPTx Philips CTX Int no startup - stations will not store. Battery. Philips CTX LINE INSTABILITY ON VCR PLAYBACK ADJUST AGC PRESET R3144 Philips CTX Line tearing at top - worse on VCR. C2378 ( 1uf ) dried up. Philips CTX LINE TR SC REPLACEMENT BLOWS AFTER 1 WEEK C2531 IN CHOPPER CCT LOW Philips CTX Losing memory. Check for dry on or faulty 2.4v cell 1777. Philips CTX LOW WIDTH AND BOWED RIGHT HAND SIDE R3483 6.2ohm o.c DRIVE TO DIODE MODULATOR Philips CTX MEMORY LOSS ( CHANGED BATTERY ) M5840 MEM IC Philips CTX NO COLOUR + POOR GREYSCALE PIN 1 TDA3650 LOW ( NORMALLY 9v ) R3222 HIGH 10R Philips CTX No colour at switch on. Poor connection on TDA3560 holder. Philips CTX NO COLOUR FROM COLD , GRADUALLY INCREASES TDA3650 LOOSE IN SOCKET Philips CTX no field sync 2 hi value Rs in field sync cct o/c Philips CTX No pic - sound ok S/Castle pulse low at pin 8 of TDA3560; TDA2577 faulty Philips CTX No pic - sound ok R3584 47R fusible o/c Philips CTX No pic/sound - field collapse seen when A1 advanced 12v safety res feed to field chip o/c Philips CTX No picture - EHT ok. R35hm ( 2.2R ) o/c. Philips CTX No sound No lt supply to audio o/p chip - R3170 3R3 o/c Philips CTX No sound or picture. R3327 ( 120k ) o/c may be the set HT control. Philips CTX No sound/pic - small pic when A1 advanced R3327 120K o/c Philips CTX No timebase operation. Drys on pin 12 of LOPTX. Philips CTX No/little colour Hi res joints on TDA3560 chip holder Philips CTX POWER SUPPLY DEAD C2323 220uF 10v Philips CTX Raster - small raster. R3327 ( 120k ) o/c may be the set HT control. Philips CTX Set dead 125V ok Check for square wave at pin 11 TDA2577 if missing replace T7353 ( BF422 ) Philips CTX Sound - buzzing alters with picture content. Radiation - via unscreened audio lead. Philips CTX Startup - no start up - Intermittent on/off R3325 set HT pot dirty. Philips CTX Tripping D6583 SC Philips CTX Tripping. D6590 ( BYV95A ) s/c. Philips CTX Wrong cols - Red = purple, blue = red, grey scale ok was degauss therm dry jointed Philips CTX-E Won't stop in search tune mode Pin 1 LM339N IC7830 not going low when search button pressed - chip faulty Philips CTX-S Black lines across col pic - ok in b/w C2218 2µ2 63v Philips CX1120 Dead Insufficient line drive to turn on LOPTr - T534 BC637 low gain Philips CX1120 Display - int. DJs on earth tags 10 , 16 , 18 , L622 or tuner earthing. Philips CX1120 Sound varying. DJs on earth tags 10 , 16 , 18 , L622 or tuner earthing.
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Regards, John |