"Day in the Life" By Peter Dolman

Re-printed by kind permission of Peter Dolman.
(c) 2009 Peter Dolman & Television-Magazine Forum.

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As a born optimist, I tend look for the positive in most situations - something my (much) better half ‘Dear Heart’ lists as one of my many faults. So, true to character, on turning the key in the lock this morning, I adopted my season of goodwill approach. After all ‘smile and the world smiles with you' as they say. I'd hardly got the lights on when the first customer appeared carrying a JVC DVD recorder complete with inbuilt hard drive. Sellotaped to it was a large envelope marked ‘problems’. "Good morning Mr Lowe, how are you?" I ventured in what I considered to be a polite and sympathetic manner. He drew himself up. "How am I? Ah yes, well we always reply 'fine, thank you' to that one don't we, but actually, since you ask, I've had quite a bit of trouble" he replied grimly. His voice dropped to a whisper as he peered around. "Medical" he hissed. "And another thing" he continued, warming to his task. "Guttering.......". At that moment Dear Heart swept in, saving me from further revelations. "Good morning Mr Lowe, lovely day, how are things?" she enquired . "Ooh fine, fine, never better" he replied, shooting me a despairing glance as he retreated towards the door which she was holding open so encouragingly.
Then she pressed his machine into my grip. "Time and motion" she remarked tartly.

The JVC was a DR-MH20. Although its troubled owner’s synopsis had pronounced it dead, the machine powered up normally, the front display flashing 'loading' brightly for around half a minute, then darkening as it entered standby. However, ten minutes later when I was playing back a test recording from the DVD drive, the front display went out and all functions stopped. Looking at the power supply I noticed that the area of the PCB around IC5101, the STR-G6653 regulator IC, was discoloured and that several electrolytics on the secondary side appeared stressed. After discharging the main electrolytic, I replaced IC5101 together with capacitors 5103 and 5104 (27uF 35V and 470pf 1kV) in the primary circuit. I also checked and replaced any electrolytic with a high ESR in the secondary circuit. This restored dependable operation. Tests showed that C5103 had a high ESR reading and I concluded that it was probably the root cause of the problem, as its failure would impair circuit regulation. Due to being situated close to IC5101’s heatsink, a 105 degree type is required and I made a mental note to replace this component in any similar machine, regardless of the actual fault it came in for. I should mention here that if the input fuse has blown then photocoupler PC5101, together with R5107,8 and 9, should be replaced in addition to those components already mentioned. The symptoms displayed can include a dead or intermittently dead machine, ‘loading’ flashing constantly on the front display or unreliable record or replay – any of these problems can be caused by the above components failing by varying degrees. You’ll find a similar type of power supply fitted to a whole range of JVC DVD recorders including, for example, the DR-MV1, which incorporates a VCR but has no hard drive.

In recognition of my success with the JVC, I received permission from Dear Heart to replenish the workshop custard cream stock; thus I found myself at our local supermarket, where my eyes alighted on a less than impressive display of LCD TV’s tastefully arranged at the base of a tower of tinned dog food. Taking my place in the queue, I allowed my mind to wander back to the days when television manufacturers considered their ultimate goal to be the rendition of a perfect picture. We all had our favorite makes and models; one of mine was the solid-state Decca 60 series, manufactured around 1975. It was designed around Mullard’s first 110 degree CRT and boasted fibre glass PCB's. Performance-wise, it achieved an almost text book IF response, which was displayed with stunning detail due to the compact delta arrangement of the phosphor triads on the face of the tube. Now, thirty years on, I gazed at the flat displays before me. Flat in more ways than one I reckoned. Any CRT set displaying such a woeful performance would need to have its tube replaced and the IF fault sorted out. The pictures were devoid of real detail and looked as tired as the fading three month old Christmas trimmings which adorned my surroundings.

A terse "who's next then?" brought me abruptly back to reality and I found myself nose to nose with a straight-faced cashier. "Right, that’s six custard cream megapacks, and are you after one of them LSD tellies or what?" she enquired impatiently. Observing that her slick sales patter had been rather unsuccessful, she jerked her thumb toward the carrier bags and leaned forward. "Shall one of our packaging technician consultants pack for you?" she recited at ear splitting volume. "Who's next then?" Composing myself, I paid for my custard creams and left hurriedly. On my return to the sanctuary of the workshop, I mentioned my brief encounter with the modern world to Dear Heart. "Stop ranting" she responded brightly as she deftly coaxed a ribbon cable into position. "Ours is not to reason why. Those people are our customers too. And very soon they'll be ringing us up to ask you to please-please-please call out and connect whatever it is up to all those other unwise purchases which they made last weekend. Either that or to tutor them on the operation of some unwanted gift of a DVD player that the children bought them - because they couldn't be bothered to think of something nice that their parents really wanted". She was right of course, I reflected. It was all grist to the mill. Soon, tea appeared and the optimist in me began to return. Then her persuasive voice impinged once more on my shell - like ear. "Ummm, why don't you devote your vast abilities to sorting out the Minsters’ Tosh TV" she suggested. "They're bound to call in today...oh yes, and his wife always asks for you" she added gleefully. I sighed and heaved the set onto the bench. Vernon Minster was a quiet and gentle soul who I had a lot of time for but his wife Lettice was as mad as a dog in a bungalow.

Their set was a sprightly Toshiba 2805DBT which appeared lifeless, but I soon realised that it was only playing dead. Although there was no sound or vision, a blank raster appeared on advancing the A1 control. There were no on - screen graphics and I soon found that the remote control wouldn't return the set to standby. On checking the remote for IR output I got a nice bleep from the tester. A couple more custard creams brought me the inspiration I required. The set's microprocessor, QA01 was probably slumbering. Checks on its supply and reset lines proved normal but the SDA and SCL lines (pins 53 and 55) were at 1.5V with no activity present on them. So I set to disconnecting the devices on the bus lines one by one until, lastly, I arrived at the pins of the AV switching IC, QV01. Lo and behold, when its SCL and SDA pins were isolated, normal I2C activity was restored. It turned out that QV01 was loading the bus because the 9V supply to pin 1 of this device was missing. I finally located the 9V regulator, QV22 which, due to its size and position, had been trapped in a vice-like grip between the pcb and the black plastic scart surround which obscures most the component side of the rear AV board. Repositioning and resoldering this transistor restored full working order. I had just lifted the set over to the soak bench when the phone rang. It was Harriet, and by the sound of it she had a big problem.

A customer for many years, Harriet’s sight has begun to deteriorate of late. Although getting out and about poses little problem for her, the 21” Sony that I sold her years ago no longer provides ideal viewing. Thus I found myself in the corner of her drawing room, gazing at a 42” Techwood TWP4210 plasma TV. “Is it me?” she was saying. “Is the picture quite as it should be?” It certainly wasn’t. On the otherwise vibrant display, a vertical bar blanked around a 1” column of the picture from top to bottom. Some thirty minutes later, as I struggled manfully through the workshop with the monster, Dear Heart began asking awkward questions again. “Er, so how, actually, do those big displays work?” she enquired innocently. “Just the basics, I mean, nothing too high-faluting”.
I always liked these little chats because it gave me a chance to test my own understanding of a topic-or the lack of it! Despite her claims that she was relatively non-technical, I’d always found her questions to be intelligent and searching - just the sort that a responsive student might ask. In this instance, it also gave me a chance to get my breath back, so buoyed up by the promise of another cuppa I warmed to my task…..

“OK then, let’s begin by working back from the end result” I suggested. “The light output you see on the screen of a plasma display panel (PDP) is produced by outputs from thousands of individual red, green and blue phosphors, arranged in pixel groups of three, just like…””like on the face of a CRT” interrupted my companion. “But how come it’s so slim?”. “Well, that’s because of the makeup of the cell structure containing each phosphor ” I replied. Every cell is positioned at the intersection of an electrode lattice covering the entire area of the screen, meaning that it can be individually driven via connections situated at the edges of the display. You’ll see those when I slip the covers off that Techwood. “I read somewhere that there are over two million pixels on a high spec HD screen” she interrupted. “So how, pray, do you manage to control all that lot?” “When you put it like that it does sound like a tall order” I agreed. “but try to forget the actual numbers involved and just visualize a few of those cells. If you could look inside a typical standard definition PDP like the one I’ve just lugged in, viewing from the front, you’d see that each vertical conductor of the lattice passes down the rear of a column of cells, against the glass backplate – in this way it forms an ‘address’ electrode at the back of every cell in that column. Crossing the front of each cell are transparent ’scan’ and sustain’ electrodes, these are formed by twinned horizontal rows of the conducting lattice.
To display a complete frame, voltages are applied between these electrodes to control the activation of individual cells according to a three-step routine. Initially all the cells are simultaneously ‘set’ to clear any vestige of charges from the previous cycle of operation. Then each cell is accessed, one by one, line after line, and written to according to the content of the incoming digitized video signal until every cell in the PDP has been addressed. Finally, in the third step of the routine, all the cells are simultaneously discharged and ‘voila’. The display produces one full frame of picture, all in glorious colour”. Dear Heart’s fingers drummed thoughtfully. “I see, so although the picture information is scanned sequentially in to the PDP, so to speak, it’s not scanned out, it’s released one full screenload at a time. Sounds good to me”. Momentarily satisfied with my thumbnail sketch, she spotted me reaching for my mug and decided on one last line of attack. “So how come those little cells have to work with gas? Didn’t you tell me that tubes have a vacuum inside?” Resting her hand cosily on mine, and thereby denying me the inviting prospect of contact with my cuppa I had little choice but to continue. “Briefly, to release energy - in this case visible light photons - from an atom of phosphor, it’s necessary to bombard it with some suitable sub-atomic particle. One familiar method, used in the CRT, is by means of a targeted stream of electrons moving through a vacuum. However, in the case of the PDP, the stream of particles striking the phosphors consists of ultra violet photons, which are generated when the cells are discharged in the way we’ve just mentioned. The cells utilize Xenon and Neon because this particular combination of gases readily breaks down, or ionizes, into plasma when subjected to an electric field. One result of this ionization, otherwise known as a plasma discharge, is the production of energy in the form of ultra violet photons. The construction of each cell is such that when this discharge occurs, the ultra violet photons emitted strike the surrounding phosphor layer, which in turn generates visible light”. The grip on my hand seemed to relax a tad. Sensing the moment was opportune, I reached swiftly for my tea and made off to investigate Harriet’s Techwood problem.

On removing the rear cover, I checked the symptom once again, noting that the vertical strip in question was situated just a little to the right of centre. Even without the benefit of a circuit diagram, the positions of the seven multi-pin output connectors spaced along the lower edge of the drive pcb gave an indication as to which of them would carry signals associated with the problem. However, my ‘scope checks showed that address data was present here, suggesting that the problem must lie with the plasma display panel (PDP) itself, or just possibly with the relevant flexi cable. I withdrew the end from its connector to inspect the contacts, then realised that what I’d assumed to be a large metal fixing clamp was in fact the rear of a heat sink situated part way along the cable itself. On releasing it, I was able to gently twist the flexi cable over to reveal an encapsulated power device, plus four large surface mounted resistors. Hoping against hope, I began to reflow the joints and to my delight, one of the resistors dropped off when the tip of the iron was applied to it! Resoldering produced a complete cure. As a precaution, I decided to reflow similar joints on the remaining six flexi’s, many of which also appeared the worse for wear. Things were definitely looking up.

At that moment the door flew open and in swept the Minsters to collect their set. Vernon smiled at me quietly from the safety of a corner as his wife closed in. Her hair, piled high like a demented beehive, wobbled menacingly as she spoke. “That’s a very low doorway you have over there… you surely must receive myriad complaints about it, hmmm?” Satisfied, she broke off, seemingly lost for a moment, then her gaze came to rest on her Toshiba TV. “As you can see. …” I began. “Oh, oh I do see… yes, very clever aren’t you, you’ve given it new life!” she murmured darkly, pursing her lips like a coit. From the corner of my eye I spotted Dear Heart tiptoeing softly away with Vernon’s cheque, and he, sensing danger, was covertly retrieving the Toshiba whilst his wife was distracted. “And what is life?” she remarked to the ceiling. Then crooking a finger she beckoned to me as if to share a confidence. Imagining I’d won her over, I grinned stupidly and leaned forward, allowing myself to relax. She cupped a hand to my ear. “My father was a scientist!” she blared, wild-eyed. As I reeled back she tossed her head and, cackling manically, flounced out, her quivering hairdo narrowly missing the doorway.

Sometime later, head still ringing, I detected Dear Heart’s dulcit tones impinging on my remaining good ear. “Just look at that picture” she was saying, waving her hand toward the plasma TV which was now running on the soak bench. As we watched, a snooker ball travelled blurrily across the green baize. On a nearby CRT set the same motion was rendered cleanly. After a pause, she summed up her thoughts. “Seems to me that with the PDP, you’re producing plasma which then produces ultraviolet photons, which finally produces visible photons” she observed. “That’s three steps. Whereas with the CRT, you’re producing electrons which in turn generates visible photons…that’s just two steps. I reckon that’s why I rate CRT performance. Why can’t they design a flat panel which produces electrons directly from its cells?” “You’re wasted here” I replied. “Toshiba and Canon already have. It’s called the SED display and you’ll find one on my Christmas wish list”.

That evening, much to her delight, I reinstalled Harriet’s Techwood TV. She was really pleased with our service and to make her point, she quoted me the lines of a most appropriate piece of poetry by Ralph Waldo Emerson. Whilst admitting to her that I’d never heard the verse, I have to say, I was knocked sideways by her gratitude for what was, effectively, nothing more than us doing our job well. The following day with the wind howling and the rain falling in sheets, the workshop door swung open and a figure swathed from head to toe in heavy waterproofs entered. I glanced up nervously; certain events over the past 24 hours, had left the optimist in me a little bruised…however, I needn’t have worried. Harriet unbuttoned her hood and smiled, producing a damp parcel. “It’s for you both” she said breathlessly, placing it on the desk. “Just to say thank you”. Then, re-buttoning her coat, she was gone, striding steadily away into the storminess of the afternoon. “Come on, open it” begged Dear Heart, “it’s almost Christmas after all!” Inside the package was a framed hand written poem; the one Harriet had quoted so generously to me the day before. It read:

“If a man write a better book,
Preach a better sermon,
Or make a better mousetrap than his neighbour,
Though he build his house in the woods,
The world will make a beaten path to his door”

“Oh gosh, what a lovely compliment, that’s going to have pride of place in here” gushed Dear Heart. “Next to my bench”, she added quickly, snatching it out of my hands. I didn’t argue. Instead, I turned and looked about me - there were still numerous repairs to be sorted before Christmas, but I reckoned that although making a successful business in this trade can be tough, we were living proof that with a great deal of effort and patience, together with a naively positive attitude, it could be done. Dear Heart, sensing my inactivity plied me with liquid refreshment. “Time and motion” she grinned.