When the first batch of imported colour TV sets hit the Australian market in March 1975, there was fierce competition between the local brands (HMV, Healing, Pye, Philips, Kriesler) and those from the UK and Japan. Indeed, there was a huge shake up as one outsider, Rank Arena (a UK/Japanese consortium), offered a modified NEC NTSC chassis which made major inroads into the established market.

In addition, many new brands were either fully imported or assembled from kits in brand new factories. There was also a lot of rebadging.

National started with its M4 series which had plug-in modules and was built in Penrith. Sharp had an 18-inch model which was a monster to repair, while General produced a highly successful 14-inch portable before moving into larger models later on. Hitachi and Sony also started off with good portables. Most of the Japanese-derived sets were modified NTSC sets and were built like battleships. Some of these sets are still working now, 25 years later.

Sets Covered This Month Akai VS765 VCR. Toshiba Bazooka Model 3408H 80cm TV set. Teac MV1480MkII TV/VCR. Panasonic NV-HD100A VCR. Sharp VC-H85X Hifi VCR

The locally-designed and built sets were based on European designs which, although highly successful in their countries of origin, were not so successful here – despite being significantly upgraded for Australian standards.

AWA/Thorn started with a modified 3K5 chassis from the UK. In the UK, they produced millions of these but out here they weren’t as reliable as their Japanese counterparts. When AWA/Thorn subsequently started their Mitsubishi-designed G and K chassis, I well remember a service technician meeting at which the Mitsubishi Service Manager began by stating "Well, Gentlemen, you will all soon be out of a job"!

He was wrong, of course, but from simple monochrome sets that broke down up to three times a year, we have progressed to sets that we consider poor if they break down once in three years. However, the quality of soldering is as bad today as it was then and faulty joints are still very common. Yet, in the computer industry, they are almost unheard of – no doubt due to the widespread use of plated-though holes on the PC boards.

The early video recorders used piano key controls and came with a multiplicity of belts, tyres and rollers. As a result, they required a belt kit replacement every few years. Nowadays, everything is microprocessor controlled but the decks use flimsy plastic gears. Many faults these days are due to customer abuse, to which a lot of modern equipment is much less tolerant.

Those technicians who work with only one brand become very quick at fixing them but often they miss the bigger picture. By contrast, technicians who work on many brands are able to appreciate why some circuits are more reliable than others and often substitute more rugged components or make other modifications to troublesome circuits.

Modifications are also issued by the manufacturers but fitting them to a set that is, say, over five years old is often unnecessary (unless safety is involved). After all, if the set has lasted that long, the original circuit could not have been all that bad.

Alternatively, there have been cases where the manufacturer has produced modifications only to change them again and again. NEC did this with the earlier series of Daewoo TV chassis, eventually issuing a chart of modifications appropriate for a range of serial numbers within the same model series.

Akai is very responsive to problems in their equipment and their service agents are sent copies of service bulletins on all their products. For example, in the SX series video recorders, from the late 80s/early 90s, they were quick to pick up a problem with the fluorescent displays going dark or failing altogether. This was due to the failure of two electrolytic capacitors in the DC-to-DC converter which supplied a -35V rail.

Akai VS765 VCR

I had such a case recently involving one of the SX series, an Akai VS765. Mrs Brady had brought it in with the classic no display fault. The voltages on the fluoro segments were very low, with the normal -35V supply from plug WP1-1 down to about half its correct value. Replacing the usual culprits – C446 and C447 – with 100μF 25V capacitors restored the voltage but not the display.

When I measured the display’s filaments, I found that there was continuity but no 4V across them. Once again, it was back to the weird little DC-DC converter Akai is so fond of. I checked D416 and D417 and also the secondary track for cracks but everything looked OK. By this stage, I was rather puzzled as it was hard to understand why the -35V rail was OK but not the 4V rail.

I subsequently wasted a lot of time chasing red herrings, such as replacing D416 and D417 with RB-100AT types and fitting a 2.2Ω 0.5W resistor in series with C447. I also wasted a lot of time checking all the other supply rails and the fluorescent display itself out of circuit, but was getting nowhere.

In desperation, I started pulling out each component, testing it and replacing it. As always, these parts are the most difficult to reach and I confess that I acquired a lot of pleasure from cutting out a piece of plastic from the main case underneath the bottom cover (where it wouldn’t be noticed) to provide better access to the PC board.

Finally, my agony was over when I removed transformer L404 and found that its primary was open circuit – due to corrosion from our favourite brown goo inside the can. The reason I couldn’t measure it previously in circuit was because L405, a 1.8mH choke, is in parallel with it, masking the fault. A new transformer restored the fluorescent display and my sanity.

Good news & bad

The Strathfields had good news and bad news. The bad news was that they had an 80cm Toshiba TV set that needed fixing. The good news was that it was a height/linearity problem, a fault that I’m quite familiar with. More specifically, there are two brightly coloured 2.2μF electros that spill their insides in many Toshiba sets and cause this problem.

This job entailed a house call to attend the Toshiba monster, appropriately called the "Bazooka" (no kidding) Model No. 3408H. I didn’t have a service manual but I felt that this would be in the bag within half an hour. Silly me!

The set was sensibly placed in a large rumpus room with good access and lighting. I switched it on and confirmed the fault. I had brought along a small army of electrolytic capacitors because some models use different values.

Everything was looking good, although the chassis was unfamiliar compared with anything I had seen before. Now all I had to do was find the two culprits which should be designated C303 (1μF) and C317 (2.2μF) in small but different coloured heatshrink plastic cases. The former should be near pin 31 of the large 64-pin jungle IC (IC501, TA8659N). The latter should be near the vertical output stage (pin 2 of IC303, AN5521).

I found C317 fairly quickly, although its heatshrink colour was dark brown or black, which doesn’t stand out as well as in previous models. Anyway, I was half-way there. All I had to do was find C303 and replace it but this was where I came unstuck. Though IC501 was a 64-pin jungle IC, it was now a TA8783N and pin 31 was not connected! Furthermore, an extra 16-pin IC, designated IC371 (TA-8739P), had been added and I had no idea what this device was for!

It was also about this time that I was informed that the fault was intermittent; that after it had been on for about 10 minutes it would often come good and stay like that. This was not good news because how would I know when it was fixed if it was intermittent?

By now I was becoming increasingly pessimistic that I could fix this one on the spot. My guess was that Toshiba, in its wisdom, had scrubbed the pin 31 function of IC502 and substituted IC371 instead, as part of and parcel of some new system.

I fished out the freezer and started hitting the small electros around IC371. Fortunately, I was rewarded immediately by all sorts of vertical deflection activity, which suggested that I might be on the right track. I found and replaced C374 (120μF 25V) and C372 (0.47μF). The latter in particular was leaky but this didn’t completely fix the problem though it was a lot better and even Mrs Strathfield, who was watching, was impressed.

As I was replacing the two previous capacitors, I noticed a 2.2μF electrolytic, underneath the IC, on the copper side of the board, between pins 3 and 15. This had apparently been changed during production at the factory from its drilled and punched position, marked C372, to where it was now. When I removed it, I also noticed that its insides had spilt onto one of the copper tracks and corroded it.

Cleaning it all up, repairing the corroded copper and replacing this capacitor finally fixed the fault.

Naturally, I was relieved that I managed to get that problem sorted out in situ, as no doubt was Mrs Strathfield. At the same time, due to the intermittent nature of the original fault, I was concerned that it might recur in the weeks and months to follow. Fortunately it didn’t bounce and while going through my Toshiba service manuals back at the workshop, I found a circuit for similar models (3418DA/2529SM) which confirmed that I had done the right thing.

Teac TV/VCR

My next story involves a Teac MV1480MkII TV/VCR combination that arrived by courier with no note – not even a name and address and certainly no fault marked. I waited a day or so to see if its owner would contact me but no one did.

Anyway, when I had a moment I put it up on the bench and switched it on. The set came on for a few moments and then switched itself off (I could hear the click from the relay). However, while the set was on, the picture and sound were both good.

I removed the back and the first thing to catch my eye was the sheer volume of dust on the inside. After blowing it all out with the compressor, I located the mains input and relay on a sub board, on the lefthand side looking from the rear. Fortunately, I did have a service manual and I established that the relay switched the AC power to the TV monitor section of the set. I also established that there was no feedback from the separate self-contained TV PC board that might contain some sort of safety circuit, nor was any part of it used to power the VCR or relay circuits.

So I wasn’t looking for a fault in the TV set but rather in the relay circuit or possibly the VCR.

The relay was controlled by two transistors, which required two conditions to be met for it to switch on. First, the power switch had to tell the VCR main microprocessor to switch on the relay. Second, the 12V rail had to be there. Both these conditions were being met for a short while but measurements soon indicated that both disappeared simultaneously after about 30-60 seconds.

For a while, I suspected that the two transistors might be faulty and spent some time checking them. However, this seemed unlikely, as the set switched on and off repeatedly in exactly the same manner which told me that something else was instructing the microprocessor to turn the set off. This wasn’t good news – access to the microprocessor is quite difficult and involves removing the Funai VCR deck and all its boards.

I was about to do this when I noticed that a videocassette was still inside the machine, so I tried to eject it. However, despite actually making a lot of promising noises, it was unable to perform any function before the set switched off. I really needed the tape out before I could disassemble the machine, so I wound the cassette carriage ejector pulley by hand until it was out.

I wasn’t sure what the loading motor would do now – after all, the carriage was now up but the mode select switch would remember it as being down. In view of this, I decided to power up the set to see what would happen. I reasoned that it would be best to deal with any loading logic problems immediately, before things got out of hand.

Fortunately, the VCR only gave a few whirring sounds from its gears before settling down and stopping. There was hardly any major movement.

The interesting thing was that the set now stayed on and was still on five minutes later. Being rash, I decided to tease the VCR gods by re-inserting the same tape and seeing if I could recreate the fault. But I couldn’t make it misbehave – the set stayed on and the tape played flawlessly.

So what actually happened? Well, it’s one of those boring old stories I rarely write about – the belts were old and worn and prone to slipping. The mechanism had jammed in no-man’s-land and the microprocessor had switched the set off – elementary, my dear Watson. Strangely, the owner still hasn’t phoned but I’m quoting for a new belt kit and a couple of hours work.

Panasonic VCR

Some time ago, I reported on a Panasonic NV-HD100A VCR that had noise on standard playback (SP) but was OK on long play (LP). I cleaned the heads but that made no difference and finally diagnosed, located and repaired a hairline fracture in the solder on pins 1, 2 and 3 of plug P502 of the head amplifier. I discovered this by wobbling the head amplifier in situ until the picture came good.

Resoldering the joints appeared to fix the problem because I left it on soak test for days before the client picked it up and everything was perfect. I didn’t think any more about it until just over three months later, when the owner phoned to complain that it was doing the same thing again. It was the same old routine emotive story that I’ve heard many times – the fault was exactly same and they had hardly used it, etc, etc.

So why did they wait until it was out of warranty to report it? I didn’t press the point and as my policy is to always give the customer the benefit of the doubt, I told them to return the set and I would check it out. They came in the next day and I checked it out in front of them, fully expecting it to be some other symptom that they were not astute enough to identify.

My arrogance was quickly crushed when I discovered that it was indeed exactly the same fault as before. Just in case, I removed the covers and cleaned the heads and it was still crook. I then wiggled the head amplifier and the fault came good. Well, these people had a point; I would have to investigate further and they would have to leave it with me.

How could a resoldered faulty joint or fracture break again? It definitely wasn’t possible and there had to be some other explanation.

I took the head amplifier out of the K chassis mechanism/deck and examined it more carefully under a magnifying lamp. I was pleased to see that there were definitely no more suspect joints but where to from here? The head amplifier plugs into the lower head drum assembly PC board, which carries the static coils of the rotary transformer. I hoped these weren’t open circuit – being a hifi VCR, their cost would exceed the price of a new VCR. How would I explain that?

Next, I removed the entire cylinder (upper and lower assembly), after first removing the antistatic wiper and auto head cleaner on the top. There are only three screws underneath to release the mechanism, plus the plugs and sockets.

With the assembly upside down on the bench and with its cover removed, I could now clearly see a row of suspect joints, especially along the plug sockets. In fact, the entire board was poorly soldered and even the rotary transformer winding terminations looked crook. I reworked the entire board very carefully, then reassembled and tested the deck.

Once again everything was working properly and after soak testing it, I returned the set to its owners at no charge.

That’s not all

I thought that that would be the end of this saga but they were back on the phone just six weeks later. As before, they trotted out the familiar routine, complaining that it was exactly the same fault as before, that the set had never been right, etc, etc.

I cut them off at the pass by telling them that if they brought it in, I would look at it straight away. Surely lightning couldn’t strike twice at the same spot, I thought. They were around in the blink of an eye and although they were icily polite, I sensed that something was different.

When I tested the machine, it turned out that the tape was jamming inside. So much for their complaint that it was "doing the same thing as before". I removed the cover and there, staring right back at all of us, was a cassette label stuck over the idler in the centre at the bottom of cassette carriage. I pulled it out with a pair of pliers and, without comment, passed it to the more vocal of the pair. I then connected the VCR to a TV set, put in a cassette, made a recording and played it back right in front of them.

Bashfully, they took their machine and, with tails between their legs, made for the exit.

As a PS to this story, I have had similar faulty joint experiences with this type of failure on two subsequent K chassis Panasonic VCRs, so this may be a common problem.

Sharp hifi VCR

Mr Andriotti has no less than two Sharp VC-H85X hifi VCRs and both were not only faulty but had the same fault. Because of this, he felt that he should get a discount for bulk repairs but I felt the opposite. In the end, we agreed that we would wait until I had diagnosed the fault(s).

He described the sets as "dead and whistling". The first one I looked at was doing precisely that and the whistling was coming from the switchmode power supply cage on the righthand side.

Removing the power supply from the rest of the VCR was difficult as it is hard to get it past the top PC board. Eventually, my persistence paid off and I finally got it onto the bench and removed its covers.

The main suspect

It didn’t take long to identify a leaky 47μF 16V electrolytic (C913) as the main suspect. Refitting the power supply into the VCR took longer than replacing the capacitor but eventually it was back in and the set returned to life. I checked all the functions and everything worked OK, except that rewind was slow towards the end. I put this down to belts and decided that they should be replaced, subject to haggling with Mr Andriotti.

I reached for the next VCR and plugged it in but it burst into life immediately. I decided to look at the power supply anyway and C913 was even more leaky that its sister in the first machine. I replaced it but when it came to checking the set’s functions, it was worse than the previous one. I removed the base cover to check the state of the reel idler belt and discovered that it was worn. In addition, the capstan motor plastic pulley was cracked and slipping.

Armed with these facts, I sought out Mr Andriotti and after some light banter, we settled on an amicable deal which involved changing the belts and tyres and gluing the pulley. As it happened, when I checked the first VCR, the same plastic pulley was also cracked.

By the way, I am fairly certain that this pulley is now available as a spare part, although it is not in the service manual except as part of the capstan motor assembly. It’s possible that the replacement is similar to the Mitsubishi one – a brass pulley which costs an arm and a leg.

Gluing it seemed to be the cheapest way.