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Old 16th Dec 2018, 2:37 pm   #81
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Back in post #65 you said that the burning smell was accompanied by the picture going dim. Is it now working again? If so burning dust is the most likely cause.
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Old 16th Dec 2018, 2:39 pm   #82
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I haven't turned it on as I didnt want to risk it, I'll test it now and report back.

Thanks.
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Old 16th Dec 2018, 2:41 pm   #83
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Default Re: CRT is brighter to one side [Hitachi CTP213]

The PCB (Printed Circuit Board) will be mounted in the centre of the TV, most likely on a chassis. TV's of this generation typically have a metal chassis.

As Lawrence has said, do be careful.

You may find glue holding long-ish wire(s) in place on the track-side (sometimes referred to as the solder-side) of the circuit board, worth looking at any main PCB's or Sub-PCB's, the latter are much like daughter 'cards' in a desktop computer.

It wasn't uncommon to find TV's modified in this way by the factory, over a production run.

Mark
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Old 16th Dec 2018, 2:42 pm   #84
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by InsertNameHere View Post
I haven't turned it on as I didnt want to risk it, I'll test it now and report back.

Thanks.
I wasn't suggesting you should do that as I'm no vintage TV expert.

If I were you I'd await advice from someone more knowledgable.
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Old 16th Dec 2018, 2:55 pm   #85
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Oh oops. I’ve turned the TV and there is no burning smell, however the picture is “smeared” and there is a humming/buzzing sound from the speaker. I'll attach some photos, showing the smearing.

Thanks for explaining the PCB, I'll take another look in a minute, if I do see the glue, should I remove it, as Mark said cures it, or leave it?

Thanks
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Old 16th Dec 2018, 4:02 pm   #86
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Default Re: CRT is brighter to one side [Hitachi CTP213]

It may also have a problem with the line driver capacitor.
C738 close to T702/TR703.
It is likely to blow the power transistor driving the line output transformer.
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Old 16th Dec 2018, 4:47 pm   #87
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I can see C736, but i cannot see C738, I think I’ll need to take the board out, but I'm not sure if i can without disconnecting all wires, which I don't mind doing, if it needs to be done.

The wires are attatched to plastic connectors, do these just push in and pull off other connectors, or do these get soldered on? Don’t want to try and take one off and break anything.

Thanks
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Old 16th Dec 2018, 5:09 pm   #88
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Default Re: CRT is brighter to one side [Hitachi CTP213]

It looks like 738 to me.
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Old 16th Dec 2018, 5:37 pm   #89
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by Refugee View Post
It looks like 738 to me.
Thank you, I've been using my phone for the day, and I couldn't read it properly I've come on to my PC, where I can read it properly.

In my earlier reply, I meant that I could see C736 on the board, but not C738. I'm not sure if they're close together

I'll find out what capacitors I need and hopefully order them tonight or tomorrow.

Edit: Looking at the service manual, looking at the replacement capacitators needed, the voltage is said to be "DC160WV" but looking online, no listings have WV, which I believe is Working Voltage? I've searched whether WV and voltage is the same thing, but no answers have been given.

My question is, are they the same? I just want to make sure.

Thanks.

Last edited by 19Seventy7; 16th Dec 2018 at 5:56 pm.
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Old 16th Dec 2018, 7:08 pm   #90
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Default Re: CRT is brighter to one side [Hitachi CTP213]

You're right in that WV stands for working voltage. In this instance the capacitor is rated at 160V.dc So there there should not be any more than 160Vdc across the capacitors terminals. Much more than this and the cap' is likely to rupture or even explode! Simply choose this voltage or higher and you should be OK.

Back in the seventies I used to service these sets. The thing was that they hardly ever went wrong. Hence 'common faults' that we can remember now were few and far between. What I would say is if the line driver capacitor is failing, normally one side of the the picture is squashed and compressed, and it will make the line output transistor run hot or fail. From what I can see from your pictures, the problem would be in the RGB output stage, of which there are references earlier in the thread.

Please do be careful with these sets, I've lost count of the number of shocks I got over the years with 'live chassis design'. SJM.
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Old 16th Dec 2018, 8:19 pm   #91
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
What I would say is if the line driver capacitor is failing, normally one side of the the picture is squashed and compressed, and it will make the line output transistor run hot or fail. From what I can see from your pictures, the problem would be in the RGB output stage, of which there are references earlier in the thread.

Please do be careful with these sets, I've lost count of the number of shocks I got over the years with 'live chassis design'.
That explains a lot about the burning, luckily it seems to be okay now. I'll replace the LD capacitor, which I think was the original issue? I'm not sure, but iI'll go back and check.

I think I should be okay replacing them as I have soldered before, and I have always got this forum or the internet should I need extra help.

I'll be very careful, I usually unplug electronics when working on them, turn them on to test, and if I need to work on it, turn it off again.

The TV will be unplugged when being worked on, and only plugged in when testing and when in use.

Thanks
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Old 16th Dec 2018, 8:36 pm   #92
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Default Re: CRT is brighter to one side [Hitachi CTP213]

It is capacitor C738 that needs replacing?

Just want to make sure.

I also apologise if I'm asking silly questions, I just don't to get anything wrong.

Thanks
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Old 16th Dec 2018, 9:35 pm   #93
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Default Re: CRT is brighter to one side [Hitachi CTP213]

You're not asking silly questions! C738 appears to be connected to the 110Vdc main supply rail. It's function is to decouple any line frequency pulses that may appear on the supply from the line driver stage as shown in the thumbnail diagram. R725 next to C738 drops the 110v supply to the driver stage T703. R725 will run warm. C738 looks like a 100uF at 160Vdc.

I'm not sure what test gear you have, but a check on the base and collector voltages of T703 would reveal if there is an obvious problem in that area.
Again, switch off, unplug, wait, then connect a meter to the transistor. Then switch on and take note of the readings. Don't take use a meter probe with the set on, you'll end up with a shock. Connect/disconnect with the set off.

Some really clear pictures of the screen, with the phone looking directly at the screen would help. Distortions of the picture help us know what bit of the set is at fault. So a good straight view of the screen is good.

If you do not feel confident at this then please don't go any further. SJM
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Old 16th Dec 2018, 9:46 pm   #94
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Oh that's good.

you were correct in that C738 is a 100uf 160Vdc, as the replacement parts section of the circuit diagram states. I've been referring to that a lot.

I do not currently have any test equipment, but I can easily get some. What is the recommended gear? Would a Multimeter work? When I do test, where do I connect the meter?

I'll reconnect the Atari now, and take some photos, I cannot guarantee that it'll be the best quality as I don't have a camera, other than my phone.

Thanks
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Old 16th Dec 2018, 9:47 pm   #95
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I would leave C738 for the moment, I would post some clear photo's of the screen display with a signal input correctly tuned in and with the colour control turned to minimum.

EDIT: Post crossed.

Lawrence.
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Old 16th Dec 2018, 10:06 pm   #96
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Default Re: CRT is brighter to one side [Hitachi CTP213]

photos:

The first two are with all 4 controls highest

The second 2 are with all three, apart from colour, which is as minimal as possible, controls on the highest.

That blue tinge is there, and isnt to do with the camera.

There is also no “snow” on the screen when nothing is connected. It just looks like the TV is off

Thanks
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Old 17th Dec 2018, 12:10 am   #97
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Now the subject of a services wanted thread: https://www.vintage-radio.net/forum/...d.php?t=152349
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Old 17th Dec 2018, 12:34 am   #98
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Am I able to link this thread to the Request?

Thanks
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Old 17th Dec 2018, 1:56 am   #99
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Default Re: CRT is brighter to one side [Hitachi CTP213]

From the bleeding (clipping) in the picture, I think there's now even less smoothing on the supply line to the RGB stages.

When replacing higher voltage electrolytics in applications like this, I've found the Panasonic ED or EE series to be quite suitable.
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Old 17th Dec 2018, 2:40 am   #100
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I was thinking of going with some Panasonic capacitors, mainly for the reason it was the only named brand I could find, and were therefore, more comfortable buying.

Thanks
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