UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Reply
 
Thread Tools
Old 17th Dec 2018, 11:07 am   #101
1100 man
Heptode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 890
Default Re: CRT is brighter to one side [Hitachi CTP213]

The RGB output transistors, TR851, 852 & 853 are mounted on the board plugged into the back of the tube. They amplify the 3 primary colour signals (red, green & blue) to drive the tube.

The 200V supply for them is derived from the line o/p transformer (FBT on the diagram), via CR707 & R734. The supply is smoothed by two capacitors, C737 & C754. These are shown as 3.3 mfd at 315V. They will be found somewhere near the LOPT.

These will be a good first step to change as they will address the original shading fault as well. These capacitors are polarised, ie it matters which way round they go!

Looking at the circuit, the chassis metalwork is 'at half mains potential' which was quite normal for colour sets of this period. Consider this to be LIVE when the set is powered so don't touch it or connect it to anything else!

Cheers
Nick
1100 man is offline   Reply With Quote
Old 17th Dec 2018, 11:23 am   #102
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 3,775
Default Re: CRT is brighter to one side [Hitachi CTP213]

I would prepared to guess from the burning or smoking episode that one of those capacitors has got hot enough to be visibly bulging.
Refugee is online now   Reply With Quote
Old 17th Dec 2018, 11:26 am   #103
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 6,288
Default Re: CRT is brighter to one side [Hitachi CTP213]

4.7uF will be near enough if you do not have 3.3uf.
__________________
G8JET BVWS Member and V.M.A.R.S
HamishBoxer is offline   Reply With Quote
Old 17th Dec 2018, 11:29 am   #104
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

So do I only need to change C737, C738 and C754, or do i not need to worry about C738? Im happy to change any of them, as long as it means the set will work and nothing gets damaged.

With capacitors I know the negative leg is the shorter one, is there any indication on the circuit board which way round it needs to be, or i can just look at the original capacitors placement.

To remove the circuit board, which I’ll need to do, are all the wires connected to it on “push pin” rods? (I think push pin is the name for it)

Thank you for your help
InsertNameHere is online now   Reply With Quote
Old 17th Dec 2018, 12:17 pm   #105
malvision
Tetrode
 
Join Date: Feb 2009
Location: Wirral, Merseyside, UK.
Posts: 98
Default Re: CRT is brighter to one side [Hitachi CTP213]

It seems to me you do not have enough electronic knowledge to repair this tv. This not being disrespectful, but is for your own safety.
malvision is offline   Reply With Quote
Old 17th Dec 2018, 5:09 pm   #106
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

I don't find this disrespectful at all, as you are somewhat correct. I do know how to fix some electronics, and how to do so in a safe manner, it's just that this is my first ever CRT TV.

All the questions I've asked are either I don't know what's gone wrong, but some others are just me double checking, as I want to be as sure as I can.

I've been recommended to replace two or three capacitors, which I can do, as I know how to solder, and I have done so before, in technology, when I was at school. I should be able to change the capacitors, but anything else, may be a little bit out of my range.

HamishBoxer - thanks for that heads up, I've just checked online and couldn't find a 3.3uf 315v capacitor. I've found some 4.7uf 315v, though.

Refugee - I can check again, now I know roughly where to look, I'll post if I see anything out of place.

Thanks all for your replies!
InsertNameHere is online now   Reply With Quote
Old 17th Dec 2018, 5:20 pm   #107
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 3,775
Default Re: CRT is brighter to one side [Hitachi CTP213]

While the board is out it is worth adding a little bit more solder to the pins under the heavy components as these often crack and cause all sorts of faults.
Refugee is online now   Reply With Quote
Old 17th Dec 2018, 5:29 pm   #108
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

Okay, thank you.

I've checked all capacitors, and none look misshaped or damaged in any way.

Thanks
InsertNameHere is online now   Reply With Quote
Old 17th Dec 2018, 7:05 pm   #109
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 6,288
Default Re: CRT is brighter to one side [Hitachi CTP213]

The caps very often look ok on that decoupling line but they are dried up.Sometimes when removed you see like corrosion on the bottom(leakage).
__________________
G8JET BVWS Member and V.M.A.R.S
HamishBoxer is offline   Reply With Quote
Old 17th Dec 2018, 7:15 pm   #110
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

Oh alright. I'll keep an eye out for that when I'm changing them.

When I take the board out, would it be okay for me to dust, even if its lightly, just so I can see what I'm doing a bit better, as the dust is very thick in places, you can't see what's underneath.

Thanks
InsertNameHere is online now   Reply With Quote
Old 17th Dec 2018, 7:50 pm   #111
Philips210
Octode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 1,483
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi

If unplugging the CRT base board from the CRT, I was always taught it's best to first discharge the CRT final anode to the CRT's aquadag braided wire by using a heavily insulated wire such as EHT cable. The shorting lead should be kept in place as the anode can often regain charge. This operation is simple for those with experience in the TV repair business but would not be recommended to anyone without the experience to do this for obvious reasons.

It would be best to leave this repair to someone with the relevant experience or at least be shown what's involved to make you aware of the safety hazards involved. Sorry to sound dismissive but your safety is paramount.

Regards
Symon.

Last edited by Philips210; 17th Dec 2018 at 7:58 pm. Reason: extra text
Philips210 is offline   Reply With Quote
Old 17th Dec 2018, 7:55 pm   #112
Lloyd 1985
Octode
 
Lloyd 1985's Avatar
 
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 1,460
Default Re: CRT is brighter to one side [Hitachi CTP213]

You should be ok to clear some dust out, best would be to take it outside and get some compressed air and blow it out, you can buy cans of ‘air duster’ to blow it out, but it’s not very powerful, and can be quite expensive for what it is! Another option, which I use regularly, is a soft paintbrush and a vacuum cleaner, just lightly disturb the dust, and be careful around any presets, such as pots, and don’t go in there bashing the hoover nozzle on the pcb’s and components! I find just holding the nozzle close and flicking the dust with the paintbrush is good enough. Just be careful around the CRT neck as well, don’t bat it one with the nozzle as the neck will probably break off.

I have also been known to take a set outside on a very windy day and cleared dust out with the paintbrush! Works quite well

Regards
Lloyd
Lloyd 1985 is offline   Reply With Quote
Old 17th Dec 2018, 8:09 pm   #113
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

No need to apologise, I would much rather be told to not do something if it's going to cause harm in any way possible. I've put out a request on the services wanted section.

Lloyd - I'll do the paint brush trick as you suggested, it's only one board which is dusty, but that's the one under the CRT itself.

Thanks.
InsertNameHere is online now   Reply With Quote
Old 17th Dec 2018, 8:21 pm   #114
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 7,282
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hopefully you shouldn't have to remove the CRT base panel. The RGB HT de-coupling capacitors (the 3.3uF ones, circuit ref. C737 & C754) might be located next to the three wire plug and socket (circuit ref. K1 to K3) on the power/deflection board, the one with the red, black and yellow wires, those capacitors should at some point connect to pin 2 of plug/socket K, tracing back from that pin should find them.

Lawrence.

Last edited by ms660; 17th Dec 2018 at 8:34 pm.
ms660 is offline   Reply With Quote
Old 17th Dec 2018, 9:32 pm   #115
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

I can see C736 inside the TV itself, which is the cap circled in red.

I'm guessing C737 and C738 are two of the capacitors circled in blue, next to the red, black and yellow wire, (which is just underneath the blue circle.)

I cannot see the number on the actual circuit board itself, inside the TV as there is a wire in the way.

I've looked on the circuit board (Page 9 of the PDF and can see all three Capacitors but my diagram reading isn't the best.

Thanks
Attached Thumbnails
Click image for larger version

Name:	image0.jpg
Views:	80
Size:	45.9 KB
ID:	174806  
InsertNameHere is online now   Reply With Quote
Old 17th Dec 2018, 9:33 pm   #116
Philips210
Octode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 1,483
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi.

To the OP, it's worth having a look through the older TELEVISION magazines that often had guides to servicing for beginners. There was a good series namely TV Servicing: Beginners Start Here ... by S. Simon (pen name for Les Lawry Johns) This series started in the October 1977 issue and lasted until August 1980.

Another series for those with more experience called Practical TV Servicing again by S. Simon started in December 1980 and ran until November 1981.
The TELEVISION magazines can be downloaded from https://www.americanradiohistory.com...n_Magazine.htm

It's an excellent magazine for all those involved in servicing TV receivers.

As others have said, it's worth reading TV books by G.J King and Eugene Trundle who describe the various circuits in a clear manner.

Regards
Symon
Philips210 is offline   Reply With Quote
Old 17th Dec 2018, 9:49 pm   #117
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 7,282
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by InsertNameHere View Post
I can see C736 inside the TV itself, which is the cap circled in red.

I'm guessing C737 and C738 are two of the capacitors circled in blue, next to the red, black and yellow wire, (which is just underneath the blue circle.)

I cannot see the number on the actual circuit board itself, inside the TV as there is a wire in the way.

I've looked on the circuit board (Page 9 of the PDF and can see all three Capacitors but my diagram reading isn't the best.

Thanks
If you've identified C736 correctly I would say that the one next to it is C735, next to that are two capacitors of the same size, these could be C737 & C754 as was suggested earlier.

Lawrence.
ms660 is offline   Reply With Quote
Old 17th Dec 2018, 9:57 pm   #118
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

The biggest is definitely C736, as I can see it marked as that on the Circuit board.

That's good, I'm glad I've found their location.

Phillips210 - Thank you for your recommendations. I'll look into them now.

Thank you both for your help
InsertNameHere is online now   Reply With Quote
Old 27th Dec 2018, 6:43 pm   #119
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 523
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi all.

I've changed two faulty capacitors (C737 and C754) with two recommended capacitors.

I then put it all back in, and now the screen only shows blue streaks. At the moment I can only get a picture from my Atari, so I tried various games.

Any idea as to why?

Thanks
InsertNameHere is online now   Reply With Quote
Old 28th Dec 2018, 5:11 pm   #120
Vectamart
Tetrode
 
Vectamart's Avatar
 
Join Date: Feb 2007
Location: Ventnor, Isle of Wight, UK.
Posts: 86
Default Re: CRT is brighter to one side [Hitachi CTP213]

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).
Vectamart is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 2:36 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.