Philips CTX-E 20CT2226 - UK Vintage Radio Repair and Restoration Discussion Forum

ben · 9th Sep 2020, 12:44 pm

On the bench is this CTX set which hadn't been powered up for about ten years. I am trying to solve what appears to be a uPc problem. On powerup the set acts erratically, you get one of the following scenarios:

- Standby LED only with unresponsive front panel/RC controls.
- Powerup okay with seemingly full functionality
- Powerup with snowy raster only. No channel indicator. Unresponsive front panel/RC controls.
-Powerup with black raster, no channel indicator. Unresponsive front panel/RC controls and what seems to be excessive line whistle.

I have already replaced the backup battery and uPc xtal, and cleaned the tuning/micro control PCB (usual mild corrosion) which I initially thought might be the problem source. However, after checking the backup battery's charging supply, I noticed that the 12v supply, which feeds the backup battery via a dropper resistor and diodes, was low at about 3v. That would explain the erratic operation, since there's also a uPc 5v supply derived from that 12v.

So far I have changed c2850 on the incoming 12v line in case it was s/c and reseated the micro. No joy.

The 12v supply line enters the control PCB at pin 2 of connector V13. Tracing the circuit to the main PCB, it appears that this is derived from a secondary LOPTx winding. The diagram shows four 12v lines, and here I am getting a bit lost as the diagram I have is quite a poor scan and I can't easily tell by looking at the main PCB traces where the line to the control PCB originates. It would help to know which one of these lines needs closer scrutiny. Thought I'd ask before digging deeper in case anyone recalls anything or can provide me with a clear scan of the control sub-PCB....fingers crossed!

ben · 9th Sep 2020, 2:32 pm

Managed to see (by squinting!) that the 12a line feeds the sync circuits, the 12c heads to the chroma/luma, so looks like the 'direct' 12v is where to look. Next step is to measure it at source and downstream and find out what might be responsible for its being low at connector v13.

Welsh Anorak · 9th Sep 2020, 2:52 pm

Well, you're almost there it seems, as nothing would be working if the +12v line that feeds the +12a-c lines was low, so it must be leaving D6585 correctly. My bet's on the connector itself, especially if there's been corrosion in the area.

Red to black · 9th Sep 2020, 5:55 pm

Hi ben,

Philips CTX-E

For Sync and several other faults connected with +12b rail.
Check R3103 near tuner. This resistor can become in contact with
the tuner can and cause the +12b line to be shorted to ground.
R3103 could also go defective - 15 Ohm fusible resistor
(4822 111 30513).

No picture, just noise
Tuning bar will not move from extreme left hand side. No tuning volts.
Check/replace on VST panel C2800 - 27pF on pin 3 of IC7800.

No remote or front keyboard functions
Check/replace D6668 - BA317 on VST panel

here are a few faults I have listed for that chassis relevant to your fault/s

ben · 10th Sep 2020, 4:06 pm

Thanks for the pointers chaps!

Quick update. The set had recently only been coming on in the fourth scenario listed above. Voltage checks showed that across c2587 there was about a volt instead of 12v. Have replaced the BYV95 and 2R2 and had scenario 3 on powerup. Next step is to keep monitoring the feed resistor and check for any distress in case there's a short still present. I will also replace the diode D6668 mentioned by Redtoblack. Also checked R3103 near tuner - seems fine.

Will also try disconnecting the backup battery in case that is faulty. It was 'new' but had it stored for about 8 years so it could be duff I suppose.

Will keep you posted!

Heatercathodeshort · 10th Sep 2020, 6:18 pm

I was waiting for your last line Ben. I had a CTX play me up back in the shop days. I used to repair loads of CTX chassis but never had any awkward problems with them.

After changing the U/S back up battery I had a host of faults not dissimilar to yours. Eventually I unsoldered the back up battery, then replaced and hey ho, all was well! This was the first and only time I had to do this. John.

gallowfields · 10th Sep 2020, 7:45 pm

apart from the back up batteries not really had any big problems with ctx,s and saw lots .remember there was a small coil near the loptx that used to go high resistance causing wierd faults on start up etc .luckily we had the coils in stock from bandeliers of ctx components bought from sendz .been retired too long to remember the cct ref

Welsh Anorak · 11th Sep 2020, 10:59 am

Wasn't that odd coil on the GR1AX? Don't remember one on the CTX.

gallowfields · 11th Sep 2020, 3:48 pm

yes glyn you are probably right on that score my memories not as good these days

ben · 15th Sep 2020, 11:06 am

Still no further along with this one. Now the set has reverted to being stuck in standby (first scenario listed) so I will turn my attention to the 9v supply and the TDA 2577.

Thanks to G60NE Dave for the VST panel cct diagram scan!

9th Sep 2020, 12:44 pm	#1
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Philips CTX-E 20CT2226 On the bench is this CTX set which hadn't been powered up for about ten years. I am trying to solve what appears to be a uPc problem. On powerup the set acts erratically, you get one of the following scenarios: - Standby LED only with unresponsive front panel/RC controls. - Powerup okay with seemingly full functionality - Powerup with snowy raster only. No channel indicator. Unresponsive front panel/RC controls. -Powerup with black raster, no channel indicator. Unresponsive front panel/RC controls and what seems to be excessive line whistle. I have already replaced the backup battery and uPc xtal, and cleaned the tuning/micro control PCB (usual mild corrosion) which I initially thought might be the problem source. However, after checking the backup battery's charging supply, I noticed that the 12v supply, which feeds the backup battery via a dropper resistor and diodes, was low at about 3v. That would explain the erratic operation, since there's also a uPc 5v supply derived from that 12v. So far I have changed c2850 on the incoming 12v line in case it was s/c and reseated the micro. No joy. The 12v supply line enters the control PCB at pin 2 of connector V13. Tracing the circuit to the main PCB, it appears that this is derived from a secondary LOPTx winding. The diagram shows four 12v lines, and here I am getting a bit lost as the diagram I have is quite a poor scan and I can't easily tell by looking at the main PCB traces where the line to the control PCB originates. It would help to know which one of these lines needs closer scrutiny. Thought I'd ask before digging deeper in case anyone recalls anything or can provide me with a clear scan of the control sub-PCB....fingers crossed! Attached Thumbnails __________________ Regards, Ben.

9th Sep 2020, 2:32 pm	#2
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Philips CTX-E 20CT2226 Managed to see (by squinting!) that the 12a line feeds the sync circuits, the 12c heads to the chroma/luma, so looks like the 'direct' 12v is where to look. Next step is to measure it at source and downstream and find out what might be responsible for its being low at connector v13. __________________ Regards, Ben.

9th Sep 2020, 2:52 pm	#3
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,921	Re: Philips CTX-E 20CT2226 Well, you're almost there it seems, as nothing would be working if the +12v line that feeds the +12a-c lines was low, so it must be leaving D6585 correctly. My bet's on the connector itself, especially if there's been corrosion in the area. __________________ Glyn www.gdelectronics.wales

9th Sep 2020, 5:55 pm	#4
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,475	Re: Philips CTX-E 20CT2226 Hi ben, Philips CTX-E For Sync and several other faults connected with +12b rail. Check R3103 near tuner. This resistor can become in contact with the tuner can and cause the +12b line to be shorted to ground. R3103 could also go defective - 15 Ohm fusible resistor (4822 111 30513). No picture, just noise Tuning bar will not move from extreme left hand side. No tuning volts. Check/replace on VST panel C2800 - 27pF on pin 3 of IC7800. No remote or front keyboard functions Check/replace D6668 - BA317 on VST panel here are a few faults I have listed for that chassis relevant to your fault/s __________________ I don't suffer from Insanity. I enjoy every minute of it.

10th Sep 2020, 4:06 pm	#5
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Philips CTX-E 20CT2226 Thanks for the pointers chaps! Quick update. The set had recently only been coming on in the fourth scenario listed above. Voltage checks showed that across c2587 there was about a volt instead of 12v. Have replaced the BYV95 and 2R2 and had scenario 3 on powerup. Next step is to keep monitoring the feed resistor and check for any distress in case there's a short still present. I will also replace the diode D6668 mentioned by Redtoblack. Also checked R3103 near tuner - seems fine. Will also try disconnecting the backup battery in case that is faulty. It was 'new' but had it stored for about 8 years so it could be duff I suppose. Will keep you posted! __________________ Regards, Ben.

10th Sep 2020, 6:18 pm	#6
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Philips CTX-E 20CT2226 I was waiting for your last line Ben. I had a CTX play me up back in the shop days. I used to repair loads of CTX chassis but never had any awkward problems with them. After changing the U/S back up battery I had a host of faults not dissimilar to yours. Eventually I unsoldered the back up battery, then replaced and hey ho, all was well! This was the first and only time I had to do this. John.

10th Sep 2020, 7:45 pm	#7
gallowfields Hexode Join Date: Feb 2018 Location: Durham, County Durham, UK. Posts: 325	Re: Philips CTX-E 20CT2226 apart from the back up batteries not really had any big problems with ctx,s and saw lots .remember there was a small coil near the loptx that used to go high resistance causing wierd faults on start up etc .luckily we had the coils in stock from bandeliers of ctx components bought from sendz .been retired too long to remember the cct ref

11th Sep 2020, 10:59 am	#8
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,921	Re: Philips CTX-E 20CT2226 Wasn't that odd coil on the GR1AX? Don't remember one on the CTX. __________________ Glyn www.gdelectronics.wales

11th Sep 2020, 3:48 pm	#9
gallowfields Hexode Join Date: Feb 2018 Location: Durham, County Durham, UK. Posts: 325	Re: Philips CTX-E 20CT2226 yes glyn you are probably right on that score my memories not as good these days

15th Sep 2020, 11:06 am	#10
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Philips CTX-E 20CT2226 Still no further along with this one. Now the set has reverted to being stuck in standby (first scenario listed) so I will turn my attention to the 9v supply and the TDA 2577. Thanks to G60NE Dave for the VST panel cct diagram scan! __________________ Regards, Ben.