A (Valentine's) Day in the Life... By Peter Dolman

A (Valentine’s) Day in the Life…
(C) 2010 Peter Dolman & Television-Magazine Forum



For some folk, a quarter of a century may seem an eternity, but for those working in this trade it passes in the twinkling of an eye. Even the legendary James T. Kirk, aided by the able Spock and Scotty would be hard pressed to chart the time shifts that apply to our industry; one that moves at warp speed in some ways, yet paradoxically remains pretty much stationary in others. Fascinating.

Take the other day for example. I was lost in thought, toying with a cunning alternative to replacing the painter IC in an A10, when Dear Heart sidled up distractingly, waving a newspaper at me. “Bet you a cuppa you can’t guess the record time for a boomerang to return?” she smirked with a superior air. With some effort, I transferred my limited intellect from the ins and outs of the Philips muting circuit in front of me to the topic of antipodean physics. Even though the glint in her eye told me I had no chance, I did my best; after all the stakes were high. “Er, about half a minute?” I responded hopefully. “Wrong! Listen to this. ‘Brisbane, Australia - boomerangs really do come back - even after 25 years’”. She paused for effect. “Well, don’t you want to know how? It says here, ‘Officials in an Australian outback town were surprised when a boomerang arrived in the mail, along with a note from a guilt-ridden American who admitted stealing it years earlier from a museum. ‘I removed this back in 1983 when I was younger and dumber’, read the note, ‘It was the wrong thing to do, and I’m sorry’. A quarter of a century! Knew you’d never get it. Coffee for me”.

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As the kettle heated, I found myself reflecting on the way some familiar products have evolved since that boomerang set off on its 21000 mile round trip; the mixes of old and new technologies and how time flies when you’re trying to have fun in this job. 1983 was the year that the Philips/Sony compact disc format was officially launched in the UK. The new medium had pulled together PCM audio, the laser, digital error correction and optical disc technologies for the first time, producing a full 20Hz –20kHz audio spectrum (unlike the ubiquitous I-Pod, with its resort to psychoacoustic fiddle factor and bandwidth limiting). My recollections of struggling through one of the first gruelling two-day CD courses, presented by Ferguson in London, reminded me just how hard it is to find real technical information – and educators - nowadays. Then there was the day when we shut up shop to attend a memorable IEE technical seminar hosted by several audio manufacturers, all enthusing on the virtues of their latest toy. Amongst them was Huntington-based audio manufacturer Boothroyd Stuart, whose Meridian brand was, and still is, second to none. Never one to toe the line, Bob Stuart, the company’s technical manager introduced his lecture as the ‘wild card’ of the event…and in his quiet and reasoned manner, boldly went where no manufacturer had gone before, questioning the whole premise that CD and high fidelity were inseparable. You could have heard a pin drop - his words were tantamount to heresy! It turned out that his company had identified a form of digital distortion known as ‘jitter’, which abounded in many CD player designs of the day (and still does today if left unchecked). The effect arose from sampling errors brought about by reference clock instability, and through careful design techniques the problem was dramatically reduced in the hand made Meridian products that he spoke to us about.
Padding back into the workshop, tray in hand, I spotted my companion gazing inquisitively into a pricey Audio Note AN-CD1 CD player which refused to spin up on rare occasions and had been clogging up the audio bench for a couple of days as a result. “Mind you don’t burn yourself” I called, spotting her fingers reaching toward the rear right hand corner of the machine. “That’s a sub miniature valve you’ve almost got your grippers on!” Seeing her look of disbelief, I tried to explain a bit about the wacky world of high-end audio. “This particular British manufacturer feels that we’re losing something in the headlong rush for all things digital and solid state, so their designs try to make the most of analogue processing and valve technologies”. Unconvinced, she peered suspiciously, first at me, then at it, in equal measure. “See, you’ve got a fairly normal looking Sony based transport mech, some solid state servo’s and digital processing, a bit of basic 16 bit D-A conversion, apparently without oversampling, topped off by that hot little valved line-level drive stage. As I understand it, they’ve also applied their minimalist approach to the subject of low pass output filtering - if so it may well deliver some sonic products which a modern solid state amplifier, say like the Yamaha DSP-AZ9 with its 100kHz bandwidth, would drive right through to the speaker terminals! Nasty. Then again, how often do we come across valved audiophile power amps with bandwidths much beyond 20kHz? I guess that infers that it’s important to choose something appropriate for this type of player to drive”. Dear Heart looked nonplussed. “So is this the kind of thing they mean when they talk about adding ‘musicality’ with these really expensive products? A case of less is more?” “You said it,” I replied. “Less in all but price! I’m afraid I can think of better ways of spending my hard earned cash”.

Outside, a squeal of brakes heralded our next visitor. Dear Heart brightened visibly as she spotted the Interflora van skidding to a halt. Seconds later a big hairy guy hurtled in, carrying something under wraps. “Oh, how absolutely darling” she gushed, gesturing him over. “Here, let me….” Moments later her rhetoric seemed to take on a more earthy form, enough in fact to make two grown men blush. I must say I’ve never known the sight of a Technics SL1200 Mk2 turntable to have such a profound effect on a gal. Finally, once she’d stamped out, I set about discussing the fault with its owner. “Goes at 78 when it should be doing 33, always in a hurry, just like me” he boomed. “Same age too! Name’s Jim Budd”. He moved swiftly to the door whilst I followed apace, scribbling down his details and ‘check servo’ on the job card. His sense of urgency made the act of booking in a repair seem like an extreme sport. “Won’t be long will it, only I’ve just got hold of a Hawkwind original vinyl master recording” he bellowed over his shoulder. ”Just can’t wait ‘til I can hear it like it ought to be heard”. The van door slammed. “Except for all the knocking of course” he added, through a cleft in a bouquet of tulips, quivering nervously at the nearside window. ‘Check bearings’ I wrote as he roared off. Despite digital technology, even 25 years on, all is still not lost for vinyl I reflected…what a joy! A healthy and profitable CD-versus-vinyl, analogue-versus-digital debate still rages amongst both audio buffs, and also by many less driven souls who are simply still very fond of their old music collections.

A quality turntable of the 1980’s, the Technics SL1200 boasts servo controlled direct drive in which the heavy platter is an integral part of the ‘motor’. It’s a very capable and much sought after deck, featuring a pitch controllable quartz lock system and high torque operation, making it ideal for professional use. In this instance there was no servo control, resulting in runaway operation. A glance at my well-thumbed manual showed that FG feedback, derived from a set of windings under the stator, is taken to Pin 22, 23 and 24 of motor control chip IC201, an AN6680, via common-emitter amplifier Q203. Making ‘scope checks on the servo board means extending out any measuring point with a short length of wire, because during operation everything’s obscured by the rotating platter! In this case it turned out that the motor’s FG winding was open circuit.

One nice thing about this sort of well-made product is the fact that it comes apart without protesting too much! That even extends to the motor winding assembly. First release the stator coil assembly (item 6 in figure 1), by unsoldering its connections to the drive circuit board, and removing the three fixing screws as shown at the top the diagram. You’ll see the FG flexible printed circuit strip wrapped in a single turn around the former (item 7), and connected to the drive circuit board via four soldered pins mounted in a plastic base. Unsoldering them directly risks damaging the delicate winding, so it’s best to proceed by removing the former itself from the circuit board, then whilst heating each joint on the strip from the top of its respective pin, push each one down through the plastic base as quickly as possible, until the FG strip can be removed intact. The open circuit will be located near the connection points where the strip curves most sharply, and can be repaired with a thread of tinned copper wire.

To my relief the servo repair was a total success, although there was no sign of any knocking noise. Even my companion regained her composure as a vinyl rendition of ‘Bridge over troubled water’ filled the air. Leaving her looking in to the Audio Note’s problems, I returned to my bench to continue my pursuit of the unthinkable; a budget repair on a Philips A10. Intermittent sound had been the problem here, and although the painter IC is a favourite cause, this particular model initially had me fooled. It’s equipped with a sub-woofer, which is actually an active device with its own in-built power amplifier mounted in the back cover. When the fault occurred, the left and right speakers fell silent, but the sub continued on, unaffected. Filled with hope, I’d checked around IC7702, the AN5277 stereo power amplifier on the main PCB and found that pin 8 (muting) went high when the fault was present. Figure 2 shows the basics. Although the manual shows no circuit diagram for the active sub-woofer, I’d spotted that its mute line was derived from pin 98 of the painter IC, the same as for IC7702, so I directed my attention to measuring the conditions around muting switch TR7701. As I was doing so, the sub-woofer cut out! Powering the set off and on again would sometimes produce perfectly normal audio, sometimes just the sub, and occasionally silence. Confused by the intermittent symptoms, not to mention an unplanned diversion into the dynamics of boomerang flight, it had taken a while for the penny to drop. Although the ‘sound enable’ rail is common to both the main L/R and sub muting, it turns out that the specific threshold voltage at which each audio circuit un-mutes is actually different. Whilst a value of 3.5V corresponds to normal sound and 0V corresponds to mute, any intermediate voltage levels here will cause muting of the main L/R channels to occur more readily than muting of the sub-woofer. By now you’re probably ahead of me; when I looked closely at the sound enable rail, it was wandering about, due, you’ve guessed it, to a faulty Painter IC.

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So now, feeling like I’d lost a pound and found a penny, I lifted pin 98 of the painter IC, which solved the problem at the expense of the set’s mute function. When I phoned Alfred, its owner, he was happy as a clam. “Leave it like that then my boy” he enthused when I explained how much money he’d save. “That’ll do us proud. My missus reckons you’ve got things in your head that won’t come out in a comb…”

As I put the handset back on its rest, I caught sight of Dear Heart carefully extracting the Sony CD mechanism from the Audio Note player. “Found something then?” I enquired hopefully. For the second time that day, she regarded me with a superior air. “Bet you a cuppa you can’t guess…”. A feeling of déjà vu set in. “Listen dearest, if this is going to involve boomerangs or time travel, I’m not playing” I interrupted; then as curiosity got the better of me, I accepted the bet and heard her out. “Look, it’s all just down to careful observation at the end of the day” she grinned. “First of all, note that once this player is running, it never falters, no mistracking probs or anything. Right? Secondly, whenever you shut the drawer, disc or no disc, the pickup is always tracked right back until it closes that parking switch – so its system control knows where it is - then it’s sent out a little way, ready to read the TOC track. Thing is, by listening really carefully, you can hear it executing these little manoeuvres, providing no noisy oaf’s creating a racket nearby”. She shot me a glance but I remained expressionless, assuming what I hoped was an air of quiet dignity. “Go on then” I encouraged, “so what’s the buzz?” “The buzz is that once I got to know the sounds it makes, I realised that on the rare occasions it wouldn’t recognise a disc, it hadn’t moved the pickup properly” she replied. I could definitely predict when it wasn’t going to read, how about that? So then, by opening and closing the drawer repeatedly, but without a disc, I eventually saw why. When the fault’s about to happen, although the pickup travels back and pushes the little leaf switch, it doesn’t move away again, so I reckon the cheap and nasty switch is past it”.

It’s all clever stuff, this observation malarkey, I thought as I watched her replacing the faulty switch. I made a mental note to find more time to stand and stare…after all, getting somewhere slowly sure beats getting nowhere fast!

The sound of tarmac being atomised outside signalled the return of Big Jim, breakneck florist and proud owner of the now repaired Technics turntable. “That’s just the greatest thing ever, man” he enthused, shrouding it lovingly in bouquet wrapping, whilst spilling fivers all over the counter and presenting Dear Heart with a bent tulip. “I tell you, my system’s gonna go into overdrive this weekend “. I suddenly remembered his parting comment as he’d sped off that morning. “Oh, just one thing before you go…” I called out as he was halfway through the door, “about that knocking, we couldn’t…” “Not your problem pal, he interrupted, turning back, “but it’s real grief for me”. I looked at him blankly. “Flippin’ kids”, he continued, “they got no proper sense of right and wrong nowadays. Makes my life hell it does”. “What, noisy are they?” sympathised Dear Heart. “Shame that, not respecting others’ peace and quiet. Still I guess that’s life, Jim”. Jim looked confused, then light dawned. “Naw, you don’t understand love, they’re the ones doin’ the complaining, see? “My music’s so loud that the kids playing outside keep knocking on my door and asking me to turn the noise down. Miserable little sods!”

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