We had a Philips 42PF9954/68C Plasma (PDP) using a Fujitsu Hitachi high-definition display come in with the owner complaining of black spots. Sure enough, when we raised it up on our terrific new Panasonic display rig trolley – which can raise or lower the PDP (plasma display panel) to 45° or flat – you could clearly see lots of tiny black spots, which were in fact pixel dropouts.

Pixel dropouts really are no longer an issue these days – at least, not until this set was dropped in. Anyway, we checked the unit out carefully and made sure that all the voltages were correct but could find no reason for this to have happened. It was then that we started to notice a few clues that pointed to possible owner abuse. For an item as new as this, you wouldn’t expect to see a lot of scratches around the mounting screws, plus it was very dusty and grubby.

Items Covered This Month Philips 42PF9954/68C plasma TV set (PDP) – FM242 chassis Panasonic TX-80P300A TV set – EURO 7 chassis Funai Technicolor 212E VCR LG Flatron RT-21FA31 (A) TV set – MC1019A chassis Panasonic TC68V86A TV set – MX4M chassis

When we asked the client about this, he finally admitted that the unit had been fitted inside a bus and then taken right around Australia, including the back of "Woop Woop". Under those circumstances, especially considering the horrendous vibration over all those corrugated dirt roads and the heat, the set was actually performing pretty well!

The sick Panasonic

Mr Diesel’s 2001 Panasonic TX-80P300A TV set (EURO 7 chassis) weighed 74kg, so I was delighted when he and his son carried it all the way onto my workshop bench.

The set appeared to be completely dead but an initial inspection revealed nothing untoward, with no blown fuses or burnt components. I then measured the power coming into the set, tracing it all the way to relay RL801, before checking for voltages on the solenoid. I was surprised to see there was 7.5V reaching the relay drivers and in fact, I could toggle the relay using my ohmmeter as a driver. However, nothing much else was happening and one of the problems was that the U Board wasn’t switching the relay on.

At this stage, I had to make up some sort of an estimate for the repair of this set. Knowing that the U Board (and DP Board) can give problems (they are the main microprocessor boards for control and sound), it was tempting to just quote for the U Board and leave it at that. However, in this case, I would have been wrong.

Being a sensitive individual, I really didn’t want to do that without being sure and so I borrowed a U Board (with MPU IC1101 SDA6000) from another set. This substitute board produced more action, allowing the red standby LED D1051 to come on and off and the relays to click. However, there was still no EHT and the set switched back to Standby.

This set does not lend itself to easy access, so it meant quite a bit of mechanical surgery to get the D Board completely out. Using an ohmmeter, I soon found a short on the 144V rail which was due to the 2SC5591PK line output transistor (Q551). So far so good but I now had to find out why this transistor had failed.

I began by checking the tuning capacitors and D558 for leakage but these checks revealed nothing. It was only after I removed the flyback transformer T551 (ZTM77018A1) and used the shorted turns tester on pins 9 and 10 that I discovered the real cause – the transformer was up the spout.

The replacement parts arrived about a week later and I immediately fitted them. I then switched the set on, fully expecting it to be working again and only requiring some adjustments to the two focus controls and the screen potentiometers. Instead, I was horrified to find that not only did I have great difficulty in switching the set on (the remote wasn’t working) but all I could get was a weird picture that was small and out of focus (see photo). And no matter what I did, I couldn’t improve it.

I was beginning to suspect the picture tube and yoke but was once again saved by having another working set. Swapping the complete chassis soon proved that it wasn’t that so I swapped over the CRT socket board (L) but it wasn’t that either. I then swapped over the entire defection D board but again drew a blank.

By now, I could really feel my frustration level rising. I just couldn’t work out what could possibly be causing these symptoms, particularly the lack of focus. Surely this could only be an EHT problem? However, I had already replaced that entire section.

Well, I persevered, swapping between the two chassis board by board in an effort to track the fault down. It wasn’t until I got to the main motherboard (A) that I finally managed to transfer the fault. None of its modules made any difference though, including the U Board.

Well, because of the multitude of weird symptoms, I opted to replace the EEPROM IC1104. Bingo! – that was the cause of all the problems.

IC1104 has ST24LC16B.1A45 written on it and the part number is listed as 24LC16B1PA45. The only problem was that the new IC arrived unprogrammed and gave an extremely bright uncontrollable raster that would probably quickly damage the new flyback transformer if left on.

Well, what was I supposed to do now? I ordered an EEPROM read/writer from Jaycar but there were some further checks to do before this piece of equipment arrived. First, I went through our pile of scrapped TV chassis looking for a Panasonic EEPROM that was similar to the one required. Eventually, I found one in what looked like an MD-1 chassis.

Installing this in my chassis gave a reasonable picture but with a limited amount of control. However, I could at least get into the service menus and "Self Check" reported only six errors.

Fortunately, having the service manual helped in setting up the EEPROM edit mode. As I quickly discovered, this is somewhat involved. You have to go into both Service Mode 1 and Service Mode 2 before entering the EEPROM Edit Mode.

To do this, you must select Channel 99, set the OFF timer to 15, the Bass to maximum and the Treble to minimum, press the "F" button on the TV and set the volume to zero. The volume display must be ON while you simultaneously press the Volume Down on the TV and the Recall or Index button on the remote.

To get to the next menu you have to scroll down to the last menu page of Service Mode 1 (SPL, GAIN) with the RED remote button and then press the HOLD key. You then press the RECALL button on the remote and if the menus haven’t timed out in the process you should have arrived at the EAROM Editor with a large table of addresses and data.

The OPTION addresses are OE0 to OE7 and OE8 to OEF and you have to make sure that the data for each address is correct for your model in the table list in the service manual. In my case, I had five options that needed changing. You scroll with the coloured keys and channel up/down on the remote and change the data value with volume + and -. When the value is correct, you have to store it by pressing the STR button. You then exit the edit mode by turning the set off.

In my case, I had to re-enter the menus several more times to get the geometry and grey scale correct for this specific set.

It was at this stage that I suddenly realised that I had lost the sound. This was caused by dry joints on the DP Board (TVPA1727ZA) which is no longer available. The current revision is V5 which is printed on the edge of the board. The dry joints involve IC2510 – a 32 pin dual in-line surface-mounted IC – and a lot of feedthrough solder connections. This is fiddly detail work that I find difficult but necessity is the mother of invention.

Anyway, that finally fixed all Mr Diesel’s problems but as you can appreciate, a job like this is extremely difficult to quote for without actually doing all the work first.

Ironically, I found out later that you can obtain the EEPROM pre-programmed for less money than the empty one. The correct part number for the TX-80P300A is TVRJ2A021 which is no longer available but is substituted with TVRJ2A007 for the TC-68P22A.

VCR formats

In 1980, the VCR manufacturers were in a huge mess over which format standard to adopt – VHS, Beta or VC2000 – and the marketing wars were on for young and old. Suddenly, a new contender appeared with the compact CVC quarter inch (6.25mm) cassette.

This lightweight portable (3.5kg) player came out of nowhere from a small company called Funai (F612VE) and sold for around $1500! It was marketed around the world under a variety of different brands and was sold with a variety of different accessories. The camera option was either a JVC GX-44E or Hitachi GP-41D and there was also a TV tuner.

This upstart precipitated a new round of technology, including the Video 8 and VHS-C cassettes. The CVC cassette format quickly lost out and you rarely even hear of it now 26 years later.

When a good friend of mine passed away recently, his family was left with a complete CVC system, including one cassette on which a recording had been made. Hoping that this contained significant video coverage of my friend, they asked me to copy it onto DVD.

This was going to be no mean feat as the recorder no longer worked properly. This particular model was called a Technicolor 212E and the last time I had seen one of these was well over 15 years ago.

However, I was pleasantly surprised to discover a copy of the original Funai service manual buried in our archives. It had been supplied by Hanimex who were the local agents at that time.

The recorder is well built and is easy to disassemble, apart from a couple of hidden screws on the righthand side control panel. The deck I was working on had no reel torque and consequently was chewing up tapes on play and stop when the loading motor unravelled and spilt the tape inside.

Once the deck was out, it didn’t take long to discover that the problem was caused by disintegrating rubber drive belts – in particular the reel belt which had broken into several lengths on the bottom of the unit.

I thought that guessing the size of this belt would be a problem but was pleasantly surprised to discover that I still had the original parts in stock ("never throw anything out, it might come in handy" is my motto). However I wasn’t quite that lucky – my stock belt was also 26 years old and had also perished. However, it wasn’t too far gone for me to be able to measure it and order a generic one the same size.

The other four belts were also ordered at the same time and when they arrived, I quickly fitted them and reassembled the deck. I then connected a DVD recorder to the AV outputs on the power supply and made quite a reasonable copy. In fact, I was quite impressed with the performance of this machine, considering it was built some 25 years ago.

Recycling an LG

A young lady recently phoned and asked me to come and pick up her LG Flatron RT-21FA31 (A) TV set. This set uses an MC1019A chassis and the unit in question was only a few years old.

She didn’t want the set fixed, however. Instead, she wanted me to take it away and do whatever I wanted with it. The set was dead and she was recycling it the best way she knew. The cost of repairing it versus upgrading the set to an LCD or plasma set made it redundant.

Well, the set was in good condition and looked the part. And it didn’t take me long to determine that it was dead (or rather pulsating) because the line output transistor (Q402, TT2140) was short circuit.

Its replacement is part number OTR570200AA which can be substituted with a 2SD2627 or KSD5702. My only concern was what caused its early demise.

First, I pulled the flyback transformer T401 out and checked for shorted turns – it measured OK so I figured it was probably OK. That’s the problem with a shorted turns tester – it’s not a conclusive test and often doesn’t pick up shorts in the EHT overwind diodes.

It cost me an extra transistor before I woke up to the fact that it really did need a new flyback transformer as well (Part No. 6174V-6006E). My excuse is that I was seduced by the dry joints on the horizontal driver transformer and (incorrectly as it turned out) blamed these for the transistor failure.

This fixed the fault but was it really worth it? The set is now only worth about $200 new and the trade cost of the parts alone was about $75, so selling it for about $100 won’t even pay for my labour, let alone give me a profit.

It’s incredible but perfectly good technology is destined to become landfill in less than five years in ever increasing amounts. How is the planet going to filter out the dangerous chemicals before we eventually eat and drink the residue?

The corroded Panasonic

I was called out to a customer’s home to attend to a supposedly dead Panasonic TV.

When I arrived, it looked like a fairly modern silver 68cm unit but when I checked the model, it was a TC68V86A which uses a fairly old MX4M chassis. The set wasn’t dead but was only showing a blue raster with no TV, AV1 or AV2 video. Instead, there was only AV sound even though every source was working!

When I removed the back, I could see that the set had been corroded due to its proximity to the beach for most of its life. This corrosion was worse at the rear of the set, especially round the AV sockets.

I suspected that the problem was an AV switching fault but it was too hard to fix in a poorly accessible dark corner in the house. The set had to go back to the workshop and once on the bench, I used a CRO to quickly trace the fault to the AV switching IC (IC3001, M51321P) on the H Board where all the AV inputs are. A new one fixed everything.

Back to school

I was contracted for a service call to an NEC FS68T90 TV in a primary school classroom.

The complaint was that the set wouldn’t start and I thought that the repair would be straightforward. Unfortunately, I arrived while the class was in full steam and I was as much a distracted by the kids and their antics as they were by me.

The first thing I noticed was a little box marked "Video Commander" screwed to the top of the back shell of the cabinet. "What the heck is that?", I thought.

The next thing I noticed was that the power cord from the TV set was plugged into this box, which in turn was plugged into the mains wall socket. I unplugged the TV from the box and connected it directly to the wall socket, switched the TV on and it worked OK. Obviously, there was nothing wrong with the TV; it had to be the box.

It took a little while before I understood what was happening here. The school had recently been upgraded and a computerised system had been installed which was controlled in the library. When a teacher wanted to show a particular video to a class, he/she would book that video in the library which would then route it into that classroom via the Video Commander at the time requested.

It initially struck me that such a system was a little bit of overkill in terms of complexity and resources. Why not have individual VCRs and just borrow the tapes?

On second thoughts, it’s probably an excellent scheme. There’s no chance of the tapes getting lost and the number of VCRs required is dramatically reduced, along with their maintenance requirements.

Perhaps the "guvmint" really knows what it’s doing after all!