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Old 9th Jun 2020, 3:41 pm   #1
kayler333
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Default Pye CT450

Just picked up a pye ct450 great condition, all works ok apart from each side of the screen is nipping in creating a distorted warped picture I've heard this is pincushion,the set hasn't been used for many years could this just be an adjustment?
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Old 9th Jun 2020, 4:25 pm   #2
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Default Re: Pye ct450

This is Philips G11 chassis which has PIN cusion distortion adjustments located on the Timebase/Decoder/IF panel located LHS viewed from the back.

The adjustments are: R2137 E-W centre, R2123 E-W Corner.

The procedure, viewing a test card or similar, is to set R2123 fully anti clockwise viewed from the component side of the panel. Adjust R2137 to straighten the vertical lines at the edge of the screen. Adjust R2123 to adjust the vertical lines at the corner of the screen, finally adjusting R2137 as necessary to maintain overall straightness.

Should the controls have no effect, then there may be a fault in the E-W Raster Correction circuit which subject to your skills can be walked through.

The service manual and circuit description can be found on the web.

Good luck

Chris
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Old 9th Jun 2020, 4:46 pm   #3
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Default Re: Pye ct450

Thanks chris as soon as I get a chance I will have a look many thanks
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Old 10th Jun 2020, 9:06 am   #4
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Default Re: Pye ct450

Just made the adjustment but to no effect so looks like a fault
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Old 10th Jun 2020, 9:42 am   #5
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Default Re: Pye ct450

Can't remember the transistor type now (after 30 years) apart from BDxxx something or other. It's the E/W driver and can fail sometimes taking a coil with it that melts and bends over.
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Old 10th Jun 2020, 10:52 am   #6
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Default Re: Pye ct450

It could be a BD238? Anyway, it's on the frame (top left) panel on a flat heatsink. The coil that bends is on the line panel (top right) and is obvious if faulty. There are two large diodes on this panel, a red BYX55-600 (I think) and a flat one (BYX71?) on a small heatsink. Check these, or ideally replace them. There are modern types available, such as the BY228.
Like the poster above, I've forgotten the exact numbers, but I can dig out a manual when I'm next in the workshop.
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Old 10th Jun 2020, 12:51 pm   #7
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Default Re: Pye ct450

Ok I will take a look when I next get the chance, thanks for all your input on this it's very helpful
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Old 10th Jun 2020, 2:36 pm   #8
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Default Re: Pye ct450

For some unexplained reason the Pye versions of the G11 were a much more reliable chassis than the Philips equivalent. The channel selector unit gave very few problems and they didn't seem to suffer dry joints anything like as much as the Philips. I had very few problems with them.

I'm not sure if the Pye versions were produced at Lowestoft?I seem to remember the printed panels being red rather than green. John.
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Old 10th Jun 2020, 7:20 pm   #9
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Default Re: Pye ct450

If the serial number on the back starts with the letters HU then it was made inLowestoft. I vaguely remember reading somewhere that the Pye factory had started to pre heat boards before wave soldering so maybe this reduced the potential for dry joints.

Make sure the big smoother is a good one or you will destroy the tube with a flashover.

Cheers

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Old 24th Nov 2020, 4:00 pm   #10
kayler333
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Default Re: Pye ct450

Can anyone confirm that the transistor I'm looking for is a bd238 please
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Old 24th Nov 2020, 4:02 pm   #11
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Default Re: Pye ct450

I've found a transistor on the left hand panel viewed from the back on a 2 inch or so heat sink, theres no number printed on it
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Old 24th Nov 2020, 5:24 pm   #12
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Default Re: Pye CT450

And are the diodes that need checking d132 and d133, what are the replacement parts for these? I'm just trying to get as much info together before I take the tv back to the shop for repair, the coil has been replaced so far but to no effect
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Old 3rd Dec 2020, 3:18 pm   #13
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Default Re: Pye CT450

Just picked up the tv from the shop, the guy said it was down to a fast acting diode, I saw it working in the shop, when I got home and plugged the set in it was back to the corners being stretched out again? This is frustrating
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Old 3rd Dec 2020, 4:29 pm   #14
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Default Re: Pye CT450

If the CT450 was working in the repair shop but it failed to work when you got it home I would suggest the actual fault is a dry joint on the timebase board.
Failing this, as previously suggested I would suspect a faulty/intermittent E-W modulator diode, D3132/33 types BYX55-600 and BY223. I had a number of these fast diodes develop intermittent faults usually O/C that could catch you out.

If the bridge coil L1337 is in good condition physically the next check is the BD238 E-W driver transistor. You may have to check the amplifier transistors 2119-BC148C, 2119-BC158 and 2149-BFX85 but it is rare to discover faulty transistors in the amplifier stages.

This should lead to a satisfactory conclusion. The G11 is quite straightforward once you know it's weak points and how to solve them. You need a full service manual and circuit description if you are unfamiliar with the G11 series.
John.
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Old 3rd Dec 2020, 4:57 pm   #15
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Default Re: Pye CT450

Maybe dry joints then will check when I get a chance cheers
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Old 3rd Dec 2020, 5:00 pm   #16
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Default Re: Pye CT450

Looks like the 2 diodes have been replaced d3132/33, after which it worked will check the soldering thanks
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Old 3rd Dec 2020, 6:27 pm   #17
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Default Re: Pye CT450

One of the diodes may have failed if they were NOS. You need to resolder most of the joints on the timebase panel. You can't 'check' them as such. I repaired endless numbers of these for around 10+ years. J.
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Old 7th Dec 2020, 11:21 am   #18
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Default Re: Pye CT450

Is the flat diode a by223 or byx71, I'm thinking it's more the by223 thanks j
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Old 7th Dec 2020, 1:15 pm   #19
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Default Re: Pye CT450

The tv is now back at the shop, he is going to replace the transistor bd238 the byx55-600 and the by223 diode, we couldn't find any reference to a by228 modern equivalent being used in this part of the tv so are sticking to the proper components, he did try a by228 but all that did is kill the set (no ht) so guess it's taken out a fuse
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