Philips KT40 Width Control. (Actually a K40). - UK Vintage Radio Repair and Restoration Discussion Forum

allybags · 27th Mar 2018, 12:38 pm

Any advice on how to reduce the picture width on a Philips KT40 TV much appreciated. On older TV's there used to be a Width Control Pot. but not that I can find on this model. I have a circuit diagram but need some clues as to which panel and part of the circuit I should be looking at.

Philips210 · 27th Mar 2018, 2:13 pm

Hi

I am not aware of a KT40 chassis. There used to be the series known as System 4:

KT4 chassis 14, 16 and 20" AX CRTs with 90 degree deflection

K40 chassis 22 and 26" 30AX CRTs with 110 degree deflection.

If you can confirm which chassis you have, I'll then give further info.

Regards
Symon.

Maarten · 27th Mar 2018, 9:35 pm

Usually, 90 degrees chassis don't have a width pot since that is connected to the EW correction which they don't have. I think this goes for the KT4 as well (I don't have a schematic handy right now).

In case of excessive width, there's probably some loose solder joints or a defective capacitor in the line output stage. Even though a KT4 won't set fire to the chassis frame or backpanel immediately, it is advised to go over all soldering in the line output stage and power supply. There will be loose joints for sure.

allybags · 29th Mar 2018, 8:49 am

Hi Symon,
My TV is the K40 chassis 26" 30AX CRTs with 110 degree deflection.

allybags · 29th Mar 2018, 8:53 am

Hi Maarten,
As the TV is of modular construction can you advise the module type number of the line output to be looking at for loose joints? Many thanks Alan

Philips210 · 29th Mar 2018, 4:20 pm

Hi allybags.

On the K40 chassis, the width control pot is R3174 located on the Large Signals Panel. It's the 'L' shaped board with the diode split LOPTx fitted.
I would first make sure the PSU HT voltage is correct, this being set with R3138 for 140V at connector N2 (Point 1).
It's possible there's a problem in the EW circuit around T7170, T7171 etc. I would check the condition of the various capacitors in the line output stage such as C2165 (330n), C2163 (9n1), C2164 (22n) and C2161 (1n). Check also diodes D6162 (BY228) and D6163 (BYW95B). As Maarten points out, these sets suffered a fair number of dry solder joints and are are worth going over. I used to suck off the old solder with a desolder pump and then resolder the joint for reliable results.

One thing to be aware of with the System 4 series. There were 4 different power supply boards, 2 each for the KT4 and K40. Some were mains isolated and some weren't. So if a replacement PSU board is to be fitted then it must be the correct type. Therefore some of these sets have a Live chassis so keep this in mind when servicing.

Regards
Symon.

allybags · 30th Mar 2018, 9:43 am

Many thanks Symon for your very thorough analysis and I will try to implement what you suggest after Easter.
Happy Easter to you all, Alan

Philips210 · 30th Mar 2018, 2:09 pm

Hi Alan.

The dry joint problem also applies to the power supply board so it's worth checking that too.
Happy Easter to you as well and to all Forum members.

Regards
Symon.

27th Mar 2018, 12:38 pm	#1
allybags Retired Dormant Member Join Date: May 2017 Location: Guildford, Surrey, UK. Posts: 8	Philips KT40 Width Control. (Actually a K40). Any advice on how to reduce the picture width on a Philips KT40 TV much appreciated. On older TV's there used to be a Width Control Pot. but not that I can find on this model. I have a circuit diagram but need some clues as to which panel and part of the circuit I should be looking at.

27th Mar 2018, 2:13 pm	#2
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Philips KT40 Width Control Hi I am not aware of a KT40 chassis. There used to be the series known as System 4: KT4 chassis 14, 16 and 20" AX CRTs with 90 degree deflection K40 chassis 22 and 26" 30AX CRTs with 110 degree deflection. If you can confirm which chassis you have, I'll then give further info. Regards Symon.

27th Mar 2018, 9:35 pm	#3
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: Philips KT40 Width Control Usually, 90 degrees chassis don't have a width pot since that is connected to the EW correction which they don't have. I think this goes for the KT4 as well (I don't have a schematic handy right now). In case of excessive width, there's probably some loose solder joints or a defective capacitor in the line output stage. Even though a KT4 won't set fire to the chassis frame or backpanel immediately, it is advised to go over all soldering in the line output stage and power supply. There will be loose joints for sure.

29th Mar 2018, 8:49 am	#4
allybags Retired Dormant Member Join Date: May 2017 Location: Guildford, Surrey, UK. Posts: 8	Re: Philips KT40 Width Control Hi Symon, My TV is the K40 chassis 26" 30AX CRTs with 110 degree deflection.

29th Mar 2018, 8:53 am	#5
allybags Retired Dormant Member Join Date: May 2017 Location: Guildford, Surrey, UK. Posts: 8	Re: Philips KT40 Width Control Hi Maarten, As the TV is of modular construction can you advise the module type number of the line output to be looking at for loose joints? Many thanks Alan

29th Mar 2018, 4:20 pm	#6
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Philips KT40 Width Control. (Actually a K40). Hi allybags. On the K40 chassis, the width control pot is R3174 located on the Large Signals Panel. It's the 'L' shaped board with the diode split LOPTx fitted. I would first make sure the PSU HT voltage is correct, this being set with R3138 for 140V at connector N2 (Point 1). It's possible there's a problem in the EW circuit around T7170, T7171 etc. I would check the condition of the various capacitors in the line output stage such as C2165 (330n), C2163 (9n1), C2164 (22n) and C2161 (1n). Check also diodes D6162 (BY228) and D6163 (BYW95B). As Maarten points out, these sets suffered a fair number of dry solder joints and are are worth going over. I used to suck off the old solder with a desolder pump and then resolder the joint for reliable results. One thing to be aware of with the System 4 series. There were 4 different power supply boards, 2 each for the KT4 and K40. Some were mains isolated and some weren't. So if a replacement PSU board is to be fitted then it must be the correct type. Therefore some of these sets have a Live chassis so keep this in mind when servicing. Regards Symon.

30th Mar 2018, 9:43 am	#7
allybags Retired Dormant Member Join Date: May 2017 Location: Guildford, Surrey, UK. Posts: 8	Re: Philips KT40 Width Control. (Actually a K40). Many thanks Symon for your very thorough analysis and I will try to implement what you suggest after Easter. Happy Easter to you all, Alan

30th Mar 2018, 2:09 pm	#8
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Philips KT40 Width Control. (Actually a K40). Hi Alan. The dry joint problem also applies to the power supply board so it's worth checking that too. Happy Easter to you as well and to all Forum members. Regards Symon.