Repairing televisions

wolsty

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#1
I hate to throw anything away and have three dead televisions in my grarage.

I've just retired and, having some spare time and a basic knowledge of electronics, I thought I'd try to improve my understanding of how these black boxes work. I don't want a second career in tv repair, but I am very interested in the technology for its own sake. Does anyone know of good on-line tutorials/idiots guides, or any other sources of help/information which would help me in my quest for knowledge.

At the moment, I'm trying to understand the workings of the psu on a Mitsubishi CT-2525TX television.

All suggestions gratefully received.

wolsty
 

zansi

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#2
Whats your problem with the Mitsi? prone to capacitor failure in PSU.

I would suggest a block change of all caps in PSU section.


zansi
 

wolsty

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#3
Thanks for the response, zansi.

The tv was given to me by a friend when he upgraded. He said it had a faulty switch but, when I tried it, there was no problem and it worked faultlessly for about six months. Then it failed. When I opened it up, there was a very obvious dry joint (scorch marks and evaporated solder) on the diode connected across the chopper transistor. I tested some of components with a multimeter and replaced the obviously faulty ones (diode, transistor and some resistors) as well as, for good measure, the IC controller, although I have no way of testing this item. I couldn't find a faulty capacitor, although this is probably due to my inexperience.

The psu is still dead, although the thermistor which controls the degaussing coil operates at switch on.

Any suggestions?

wolsty
 

zansi

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#4
The capacitors are only checkable with a ESR meter, but for the low cost involved, its feasable to replace all in the psu, (about 10)

zansi
 

wolsty

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#5
OK, I'll try it. I have to buy all my electronic components by mail order, since I live in Cornwall and have no supplier within about 70 miles (there's a small Maplin in Plymouth, but I don't get up there very much). P&P is normally a large part of any cost when I buy a small number of components. Do you know of any suppliers who don't charge £2.50 and upwards for orders under £30.00?

wolsty
 

Channel Hopper

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#6
I though there was something suspicious about this site, everyone seems to have come from the TV repair scene - myself included

Try this website for all helpful hints on repairing TVs and Videos

http://www.e-repair.co.uk/tips.htm

What other sets do you have
 

BarMoo

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#7
LOL !

Zansi you suprise me :-) You engineer, you.

Have Fun,

Mark.
 

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#8
Heres what the website says

Int dead especially when cold

Check / replace C906 (47uF,25v), C905 (220uF,25v) and C912 (4.7uF,50v)

Looks like you were right !
 

wolsty

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#9
Thanks, Channel Hopper. I didn't know of the existence of this site, but it looks interesting. I'll try the recommendations.

I have a Ferguson 51P7, which has no picture but a distorted (beyond recognition) sound output and a very, very old Philips 22 CS 5740, which works, but has a channel display which rarely shows the channel selected and has a clapped out remote control.

wolsty
 

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#10
I got out of the TV repair business once I found satellite installs. With the price of TV tubes from the Far East, its no longer viable to run around London collecting /repairing and re-installing

Nowadays if a customer has a TV fault I will usually suggest a new one. I can go to the local trade supermarket and buy a new 28" TV (multi system SECAM/PAL, and multi standard VHF/UHF) for under £180 and they will throw in a 2 year guarantee

A good wide screen TV are often not much more than £340 with three year guarantee.

Everything from the LNB downwards is more or less a disposable item
 

wolsty

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#11
It's not the prospect of having a working television that attracts me, but the desire to understand how everything works. I'm trying to keep my brain active in retirement, on the principle of 'use it or lose it'. The attraction of a widescreen tv increases daily and, if I can persuade my wife of the virtue of watching it, I'll follow your advice.

wolsty
 

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#12
Dear Wolsty

I haven't got to retirement age as yet but I undertand what you mean.

TV repair was going to be my main line of work when I started in the late 70s however some nasty experiences
1) an Ultra Bermuda catching fire in the workshop, and refused to go out
2) an Amstrad 20" thing that had the worst PCB layout Ive ever seen (spent weeks on it)
3) EHT discharge across me on a hot summer day
4) 1 x Home callout to see a TV that had about 5" of household dust, lice and mites on top of the main circuit
5) Another callout where the customer complained of bad colour resolution, when I got there there was 1mm of nicotine all round the room and on the tube front. I had the job of cleaning it with meths and a sock
6) One further callout where the owners 15 year old cat had incontinence and promptly electrocuted itself whilst asleep on the video.


made me think long and hard The boss putting his back out whilst doing his third satellite installation in 1985 got me into this business and Im so grateful for it. As a hobby I now repair motorcycles and am getting my head around the logic of a 1957 6T, duplex chains and a rear sprocket thats part of the wheel hub (very clever)

How are you getting on with the Misubishi ?

You didnt say what your main job is/was
 

wolsty

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#13
Dear CH

Well, I’m not strictly at retirement age, but my last job was ‘restructured’ out of existence, so I took the ‘early retirement’ package. I wasn’t sorry to go, as the MD is a dickhead. Anyway, I’ve got more time to indulge my interests (satellite, sailing and popular science). My wife doesn’t protest as long as she comes home from work to a clean house and a hot meal. I do what many early retirees do and play consultant. I’m currently working on a £5m film studio project, a £3m library development and a proposal to develop a centre for teaching ‘book arts’ (binding, calligraphy, paper manufacturing, conservation etc.) My main role here is in writing applications for grant aid, mostly for money from European sources. In my spare time, I do some supply teaching, mainly for the pleasure (yes really!!) of it, although the money does help to fund my hobbies.

The satellite, tv repair, popular science stuff is all part of trying to understand how things work. I remember watching the repair-man who used to come (very frequently!) to repair our 13 channel, valve-driven, bakelite case, black-and-white, 12 inch PYE television when there was only 1 BBC channel. I’m sure his ability to swap valves and bring the picture back must have influenced me.

I get really pissed off with the arty-farties who poke fun at the ‘geeks’ and ‘anoraks’ who spend time on difficult subjects (as opposed to the waffly arts side such as history, media studies, English, etc). In any case, who do the arty-farties call on when they want someone to fix the food processor in their designer kitchen? A graduate in ‘Women’s Studies’? I really sympathise with your wanting to work with duplex chains and rear sprockets.

I took my 17 year old son to a lecture on ‘Heroes and Inventors’ by Adam Hart-Davies last Saturday. It was magnificent – lots of table-top experiments with automatic egg-boilers, stirling engines and air cannons and stories about Brunel and Stephenson. Those 19th Century engineers really knew a thing or two. Tim’s going to study aerospace engineering, so we have a lot of common interests.

Given your experiences in tv repair, I’m not surprised you gave up. Anyone who has much to do with the public in their own homes will sympathise with you and the experiences with nicotine and cat pee. The way some people live defies description. My wife is a teacher and my eldest daughter a doctor. I cringe at some of the stories they’ve told me about home visits.

As to the Mitsubishi. Slow progress, I’m afraid. I fit it in when I can, but my main problem is finding spares. I don’t do enough business to qualify for an account with any of the suppliers and postage charges make buying a few capacitors and resistors an expensive proposition. Cornwall isn’t known for its range of electronics part suppliers.

I’ve had fun teaching myself how a bridge rectifier chopper psu work, though. I used my son’s computer program, Crocodile Clips, to make up circuits and, more often than not, blow up the components. Will I ever grow up? I hope not.

wolsty
 

Channel Hopper

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#14
Dear Wolsty

Totally forgot your original request for components on the cheap in Cornwall (was actually trying to figure how to get the Ducati through its MOT with the somewhat loud exhausts - made a set of baffles in the garage that work a treat)

Try this site, www.satcure.com

You could spent days looking but the best way is e-mail Martin on the other side of the screen and he should be able to suggest what to do. He sells all sorts of ready made packs of parts for satellite repairs so theres an outside chance he may even have the bits you need off the shelf

Used to work with him years ago
 

wolsty

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#15
Martin has helped me several times and I even met him once. I called in on him on my way home from visiting my parents and he gave me a couple of old videocrypt decoders so that I could receive Ch5 on analogue. I did ask him about televisions, but he says he gave up on them when they started to use IC's! I do like his site, though, which was of enormous help in answering my many questions about satellite tv when I was even more ignorant than I am now.

I'll keep looking, although I think I now have an answer to my prayers. A friend who runs an auto-electric repair business has accounts with a couple of suppliers, so he gets his parts free of P&P charges. If I design his web site and promotional material, he'll get parts for me. He's just lent me his catalogue. It's like Aladdin's cave.

Ducati. Wow. How old is it? I used to envy the guy who lived near me when I was about 16. He had a Ducati which was a real chick magnet. I don't remember the model, but it was finished in electric blue. Every boy's wet dream.

wolsty
 

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#16
Glad to know the world is still small enough. Ive know Martin for ten or so years. His business has of course taken a bit of a pasting since the BKYB move to digital

The Duke - its a 900SL, in the usual Ducati red

Chick magnet ? bit too old and married to appreciate what it could do to attract women. Its also a single seat so its really only got one purpose.

I suspect Ill be going to the TT on it this year
 

wolsty

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#17
Ah, but when you're 16, with pimles and unruly red hair, anything that attracts the girls is wonderful. The term 'chick magnet' hadn't been coined then, of course.

If it was electric blue, do you think it had been resprayed?

TT? Isn't that dangerous?

wolsty
 

Channel Hopper

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#18
When I was sixteen even the ninth-hand moped I managed to buy from newspaper deliveries looked good. Ran it / rebuilt it/ destroyed the family flymo when I lost a spacer in the garden/ for two years and then each bike Ive got since has been either the most powerful I could afford - regardless of condition, or the apparent bargains advertised.

The 900 was bought for £1000 in five boxes with some engine damage to the crankcases. Lots of drilling and araldite later and its running (better then I had hoped) for a budget of £260. Running costs are it seems minimal, but the last owner spent a fortune each wquarter when something else would break/rattle loose and fall off. Ducati engine vibration has a tendency to unsrew anything bolted to the right hand side ( fairing covers, indicators, exhaust bolts etc)

There are some older ones that came in blue, I remember the ST2 and the 'friends' Mk III and Darmah which I had to help pushstart every cold/damp morning (we lived at the bottom of a steep hill in Plymouth circa 1983).


TT - dangerous ? - only if the wife finds out Im going without telling her ! She came once before and didnt like it so Im trying to convince her that the first week in June is an ideal time for her to see relatives out of the country.

Been twice already and its my type of holiday, I cant stand all the beach and sunbathing ones unless I can take or hire a large bike.
 

Channel Hopper

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#19
And it passed the MOT today

Will take out the baffles back out this afternoon as it strangles the engine
 

wolsty

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#20
Congratulations. It seems as if you know what you're doing. And doesn't it sound better without the baffles?

I haven't had time to look at the Mitsubishi in the past few days all this temporary work keeps getting in the way!

wolsty
 
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