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Old 28th Dec 2018, 5:42 pm   #121
19Seventy7
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by Vectamart View Post
This fault is included in the book "TV Fault Finding Guide Volume 1 Issue 6 on page 191. It refers to a model CTP230 but I suspect that the chassis is very similar. It suggests changing C719 (4.7mfd).
Okay, thank you, I'll take a look now.

Thanks for your help
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Old 28th Dec 2018, 5:55 pm   #122
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Update:

I just looked inside my TV again, looking for C719, when I came across R727, Which answered the question of, where did that burning smell come from.

Could this be the cause of the picture not working as it should, and if I change this, would it possibly cure the issue?

Thanks
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Old 28th Dec 2018, 6:05 pm   #123
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Default Re: CRT is brighter to one side [Hitachi CTP213]

That could be what made the smell! When resistors overheat its normally because something further downstream of it is drawing too much current. Most probably another electrolytic capacitor going short circuit. Just replacing the resistor will likely just burn out another resistor. Have a good look at the circuit diagram to see what is connected to it.

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Old 28th Dec 2018, 6:20 pm   #124
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Default Re: CRT is brighter to one side [Hitachi CTP213]

R727 is the feed to the CRT screen grid rectifier.

C719 is different animal in this chassis compared to C719 in the CTP230 (NP8C chassis)

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Old 28th Dec 2018, 7:13 pm   #125
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by Lloyd 1985 View Post
That could be what made the smell! When resistors overheat its normally because something further downstream of it is drawing too much current. Most probably another electrolytic capacitor going short circuit. Just replacing the resistor will likely just burn out another resistor. Have a good look at the circuit diagram to see what is connected to it.
I reckon it is, as it's on the side where the smell came from through the vents.
I never noticed it before, as it's tucked away, almost hidden.

I'm not great at reading circuit diagrams, so I'm hoping maybe someone here could tell me what it could be? I've found the resistor, and the parts before (see attached) Will I need another resistor and another capacitor, or another set of capacitors? (C727 is roughly central of the image)

Ms660 - you're right, as the replacement parts list says that my C719 is a polypropylene 0.022uF 630V capacitor, opposed to the CTP230's 4.7mfd.

Thanks for your help
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Old 28th Dec 2018, 7:33 pm   #126
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Default Re: CRT is brighter to one side [Hitachi CTP213]

On the schematic R727 is connected between pin 7 of the flyback transformer (T703) and the anode of the screen supply rectifier (CR703)

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Old 29th Dec 2018, 12:32 am   #127
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Default Re: CRT is brighter to one side [Hitachi CTP213]

R727 & CR703 provide the 800V supply to the screen potentiometer. If this 800V supply is missing, you would not get much on the screen.

R727 does look to be burnt although what you can see is a piece of sleeving over the top of the resistor. The value of the resistor needs to be measured with a multimeter to confirm whether it is OK or not. It is marked on the circuit as a 1.8K safety resistor which means it should be replaced with the correct type.

If it has failed, there will be a cause. The most likely is that the diode CR703 has gone short circuit. It could also be C731 or C850 although these are both small value non electrolytic types so are not that likely to fail. You would need to test CR703 with a multimeter to confirm if it has failed.

All the best
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Old 30th Dec 2018, 1:49 am   #128
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Oh okay, thank you, if the resistor measures correctly should it be alright to use still, even though it has possibly burnt? - Again, just want to be safe, and make sure.

I'll order a Multimeter ASAP and get to testing as soon as I can. If CR703 has gone short circuit, is it just a case of replacing, or is there other stuff down the line that will need replacing?

Thanks for your help!
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Old 13th Jan 2019, 7:32 pm   #129
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi, I have a couple of questions about my TV that I have just thought of.

1) would anyone have an idea as to why the picture stopped working AFTER i replaced the capacitors. Could it be that the capacitors don’t work, or is it just pure coincidence. There was a picture with the caps i replaced, albiet smeared.

2) when I test the voltages with the multimeter, where do i connect the “pens” from the meter onto the PCB? Is it on the solder spots to the certain component, eg resistor or diodes.

Thanks
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Old 13th Jan 2019, 7:49 pm   #130
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Did you change that diode and the safety res?
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Old 13th Jan 2019, 8:06 pm   #131
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Default Re: CRT is brighter to one side [Hitachi CTP213]

No not yet, I need to order one but havent had the time. Ill have a look now to see which one i need to order and hopefully order them

Thanks
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Old 13th Jan 2019, 8:47 pm   #132
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi, just a question about R727 and CR703

R727 - What wattage should R727 be? The main wattage I have seen is 3W.

CR703, what specifications are these as the service manual has no description for CR703.

Sorry if these are silly questions, just want to make sure.

Thanks
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Old 13th Jan 2019, 9:18 pm   #133
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I think the res is about 2W though I am sure 1W will be ok. It is of course a safety res and would be listed on a service sheet.

The cap might be a 1.5kV or similar high voltage ceramic. Very odd type is not stated.
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Old 13th Jan 2019, 9:37 pm   #134
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Okay thank you. Should I wait before ordering a cap to see if anyone else knows for sure, or should 1.5kV be okay to use?

Thanks
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Old 13th Jan 2019, 10:53 pm   #135
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
would anyone have an idea as to why the picture stopped working AFTER i replaced the capacitors
Could be all sorts of things. Possibly a specific problem with what you did, e.g. wrong caps, wrong way round, faulty caps (unlikely), something else reconnected the wrong way round while reassembling. Or on a more general note, disturbing something that did not want to be disturbed, e.g. a preset nudged out of adjustment, dry joints parting company, duff connections. Or, other parts may just be progressively going bad every minute the power is on.

Coming to this thread afresh, I'll echo what various posters have said before; you might get best results by teaming up with someone experienced in TV repair and working on it together in person. These are reliable sets and there might not be very much wrong, but there now seem to be two or three faults and you run the risk of damaging parts that are difficult to replace unless you can quickly and efficiently get to the root of them. An elderly solid-state live-chassis TV is probably not the best project to tackle until you have a fair amount of experience and familiarity with electronics such as using a multimeter, identifying capacitor polarity etc. When new, it was the most complex piece of technology in most homes, requiring skill to service, and now even more so because of its age and increased fragility.

I'm not trying to sound disparaging, keep at it, you can probably fix it with the help of the team here, just passing on my father's advice to me (which was good, he used to recruit TV engineers so he knew what it took to be a good one!)
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Old 13th Jan 2019, 11:29 pm   #136
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I would honestly prefer to have someone else help, however my dad isn't allowing me to spend much more money on it, only really for parts. The only way which I could really get it done properly is if it were free, which I know isn't fair as this is people's trades.

I of course don't want to cause any more damage to the TV, and as you may have read, this is my first ever CRT, so I have very, very little knowledge on the subject, so if I were to carry on, there is chance I will do more damage.

Thank you for your help, it's appreciated
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Old 14th Jan 2019, 12:49 am   #137
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Default Re: CRT is brighter to one side [Hitachi CTP213]

I would go looking for a cracked track on the circuit board around the capacitors that were replaced or on a component such as a power resistor close to those capacitors.
Tracks often begin to lift around power resistors.
One of the first places I would look for a lifted track would be that non flaming metal film resistor with the braided safety guard on it.
Open this link and type the value into the filter under the orange button and then click on the data sheet buttons and check the size of the part.
https://uk.farnell.com/webapp/wcs/st...6669,110124890
This will give you the wattage if it is not shown in the manual you have. Leave the lead outs long and fold them over onto the tracks and clean off a bit of the usually green solder mask and solder it to nice new copper so bridging any potentially damaged copper.
I am pretty sure that a track has lifted off the board.
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Old 14th Jan 2019, 10:24 pm   #138
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi, thanks for the reply.

I've just had a look all around the bottom of the PCB and cannot see any cracking.


As for the resistor, I think it's 2w possibly? I'm not sure so if someone could possibly correct me, i'd be thankful.


Thanks for your help
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Old 14th Jan 2019, 11:19 pm   #139
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Default Re: CRT is brighter to one side [Hitachi CTP213]

If the screen is dark and smeary, are you sure you didn't knock the SCREEN pot on or near the line o/p transformer whilst cleaning/moving the chassis? Might be worth marking the current position with tipp ex and moving it back and forth slightly then retrying.

Another good guide that this pot has been moved is if the dusty part of the control is no longer uppermost!
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Old 14th Jan 2019, 11:23 pm   #140
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Default Re: CRT is brighter to one side [Hitachi CTP213]

Someone also may have re adjusted this in an attempt to mask the original fault, which has now been (hopefully) cleared, causing the symptoms you are now faced with.
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