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Serviceman's Log

Some days bad things just happen. A fire can occur at any time and when it does, recovering valuable data from computer hard drives can be a real challenge.

By The TV Servicemam

At a glance...

  • Grundig ST84-796-9 TOP LOG (CUC 6380 chassis)
  • Grundig Vision II LXW 68-9620 Dolby G1 chassis
  • Hewlett Packard f1703 (P9620A) computer monitor
  • Apple Mac Studio Display
  • 17-inch monitor M7649

It was a beautiful spring morning and I was sitting outside the workshop enjoying a cup of coffee and a chat with a friend. Suddenly, someone shouted "FIRE!" and all hell broke loose. It was my neighbour’s factory unit and it had smoke pouring out of the roof and from the gaps around the closed doors and windows.

I didn’t have my neighbour’s mobile number but someone else did and called him. Naturally, the fire brigade was also called and while we waited, a few of the other unit owners managed to organise some water hoses.

The problem was that the place was fully locked with the roller door in the closed position, so all anybody could do was to cool the building from the outside with the water hoses. It didn’t take long for the fire brigade to arrive and they were about to break down the door with a battering ram when the owner screeched to a halt outside. He got out and unlocked the door for them and was immediately enveloped in thick acrid smoke.

The fire brigade took over from there and several men wearing breathing apparatus entered the building dragging fire hoses. They quickly extinguished the fire which was on the mezzanine floor and within about 10 minutes, the roller door was pulled up and the windows opened.

None of us in the now sizeable audience outside actually saw any flames but it was fairly obvious that the fire was now out and it was just a matter of clearing up and blowing out the smoke. After the firemen had finished, the forensic police went in and then later on the insurance assessor arrived.

It wasn’t until four hours later that I was allowed in to see the damage. Downstairs it looked as though nothing had happened but upstairs was like Armageddon. Though no-one could actually swear to it, it looked as though a mains plugpack or an extension lead had been the cause but there just wasn’t enough evidence left to confirm this.

Immediately adjacent to the seat of the fire were the remains of an elaborate computer system. I was asked to give an insurance estimate for some of the items that were damaged and was also asked to see if I could recover any of the data on some of the computers.

Click for larger image

The first item was a 2Gb USB2 fast external hard drive in an aluminium case. This had copped a lot of heat and the plastic had melted and burnt on both ends of the metal case and had to be cut away. Eventually, I extracted the IBM IDE hard drive and most of the controller card.

The USB socket was too badly fried but I managed to get a new one and fit that. I also had to replace the red HDD activity LED, which had melted.

After some cleaning, the controller card came up looking pretty good. I then connected it to one of my computers with one of my hard drives and was delighted to see that it worked OK.

Next, I turned my attention to the hard disk drive inside the case. This was still wet and was covered with all sorts of powdered debris, despite being deep inside the machine. I took it out and cleaned it up using brushes and an air compressor. It came up looking quite good on the outside so I connected it to the USB controller card and plugged it into my computer.

All I got were a few faint noises from the drive but no action. I then decided to remove the drive’s PC board which was held in place by six Torx screws. Once it was out, I was annoyed to see even more wet ash on the inside. How on earth did this get there?

After delicately brushing out the debris and flushing it with compressed air, I sprayed the corroded areas with a light penetrating oil and then blew the excess off. I then reassembled the hard drive and reconnected it.

This time the noise was somewhat louder but still nowhere near that of a working hard drive. I wasn’t game to remove the main cover on the hard drive itself as I figured this was airtight. My feeling was that the motor wasn’t spinning correctly and nothing more could be done by me. An expert would have to do the rest.

Desktop computer

The desktop computer was a Dell and had really copped a lot of heat.

Inside, the motherboard didn’t look too bad. The DVD and floppy drives had been destroyed but the hard drive looked OK. Connected to another computer, it immediately spun up OK and the data was readable.

Unfortunately, the 20-inch Mitsubishi monitor had been totalled, along with the keyboard and mouse , and was simply chucked into the skip.

There were also a couple of notebooks in the room, one of which was a write off. The other, a HP Pavilion dv9000, was borderline. It had been saturated with fire retardant but because the lid was down, it looked as though only the sides needed cleaning.

After a brief clean, it actually booted up and seemed to be working fine. However, because it had been saturated with fire retardant, I was asked to strip it down and clean it out.

That wasn’t as easy as it sounds. First, nobody ever tells you about the lingering sweet, sickly smell that permeates everything touched by smoke or fire. Second, I hate doing notebook computers at the best of times as there are always concealed clips and screws, plus there are millions of different screws which all look very similar but can only go back into their original holes.

Anyway, I downloaded the maintenance and service guide (some 300 pages) and printed out the relevant removal and replacement procedures.

Because the notebook was working, I decided to strip it down just enough so that I could see inside it and see whether it really was damaged or not. The really difficult part involves removing the keyboard and later, if necessary, the display screen, system board and power supply.

To get to the keyboard, you first have to remove all the drives and accessories and then remove the switch cover on the top at the rear. This assembly is held on by six screws in the battery compartment and then by a lot of clips.

Once the cover was off, I could access the keyboard mounting screws and remove it. I could then see about 50% of the computer and it didn’t look too bad. However, the USB socket and other sockets on the side of the case were already beginning to corrode.

What is it with this fire retardant foam that the fire brigade use? It is unbelievably corrosive and conductive too. It may put out the fire but everything else that it touches is ruined.

Once again, I used brushes and an air-gun to clean out the gunk and afterwards applied a minute film of oil over the contacts and metal brackets. I then reassembled the computer and replaced the battery. And that’s where my worst nightmare started. As soon as the battery was replaced, smoke started to pour out the lefthand side of the computer near the VGA socket!

Unfortunately, the battery fitted to this notebook is not one you can unplug and remove easily, as there is no finger grip available. Instead, you have to release the battery lock, hold the computer horizontally and literally let the battery drop out.

Once the new fire had subsided, I examined the relevant area very carefully but just could not find the source of the smoke. I then gingerly connected the external DC power supply and noticed smoke begin to come from under the VGA socket before I unplugged it.

At this stage, I really had no idea what was causing this problem except that it had to be in the power supply on the system board. So there was nothing for it but to disassemble the whole thing.

Referring to the guide, there were four major assemblies to remove. In addition, I had to unplug lots of extra module accessories. I started at section 5.4 and worked through to section 5.25. Each time I took out a part, I placed it in a box together with a bag holding the appropriate screws.

As I peeled off the layers and got deeper and deeper into the works, I began to see all the areas I had missed when cleaning, especially around the edges. Eventually, I got the system board out and removed the heatsinks and then the insulating tape covering the power supply next to the VGA board.

Well, I looked and looked but I couldn’t see any sign of a hot spot or fire. In fact, I had to power the system board up again to finally locate the source of the trouble. It was a tiny dag on the VGA support bracket that was just touching a PC board track.

Access was very difficult but I clean-ed the area up meticulously and angle ground the metal dags off the bracket so it didn’t touch. This stopped the pyrotechnics in their tracks – but had the computer’s electronics been damaged? I wouldn’t be able to tell until after another two to three hours of re-assembly.

Next I paid attention to the other areas of corrosion. The audio board was badly corroded in and around its connection plug and one of the tracks had actually been "etched" open circuit by the foam. I bridged this gap and cleaned it thoroughly.

Similarly, the power input socket and some of the extra sockets and assemblies all around the edge of the case required attention. That done, I then started the tedious task of re-assembly.

However, despite all the precautions of saving the screws with their assemblies, I found there were discrepancies between the service manual and reality. Also many of the screws looked very similar but weren’t. Then I had the hassle of reconnecting all the miniature plugs and sockets. Some of the ribbon cables were very fiddly to plug in.

Finally, when it was all back together, I had one screw and one socket left. The only trouble was the screw didn’t match the socket! Anyway, the notebook was solid – nothing rattled – it would just have to work without it.

And fortunately it did – all the functions seemed to test OK.

It was only now that I could prepare an estimate of the cost. I also realised that I couldn’t possibly guarantee that the chemical reaction from the foam would stop right there and then. In fact, it was quite likely that this computer, now working, would be unreliable, with repetitive failures due to continuing corrosion.

In the end, I decided that the only way out would be to replace both the system and audio boards. However, this would be more expensive than a replacement notebook. All that hard work for nothing!

LCD TVs & monitors

Repair work on LCD TVs and monitors is now increasing, with most repairs involving the backlight inverter power supplies. These power supplies provide the backlights with high voltage and also crudely control their brightness levels. As yet, I haven’t actually had any backlights fail unless they have been smashed due to some sort of accident.

Recently, I had a Grundig Vision II LXW 68-9620 Dolby using a G1 chassis come in with "no-picture" symptoms. However, if you shone a torch at the right angle to the screen, you could just discern an image.

This set has quite a large inverter board as it had a lot of backlights. Unfortunately though, the service manual shows no part of this circuit board as it is part and parcel of the display panel. In other words, if you can’t fix this board, you will have to replace the panel, which is uneconomical.

Fortunately, I could not detect +24V on the BUI-27 connector to the inverters. This was due to a dry joint on one side of the diode that supplies this rail on the main board and resoldering this fixed the problem.

I had similar symptoms on an HP f1703 (P9620A, probably made by Liteon) LCD computer monitor, except that the picture was intermittent. It would come on for 15-30 seconds and then go off.

This monitor used an external 12V power supply which was OK. When I stripped it down, there were only two boards inside for the inverters and the video processing and scalar drivers.

I immediately went for the inverter board, looking for dry joints on the coils, but could find nothing. I then searched the internet for a circuit diagram or service manual but again found nothing. However, I did find a lot of hits for this very problem from other owners.

Next, I tried to contact HP but only got through to an Indian call centre. They knew nothing about this problem and could only suggest I check my screen saver. They did however "cherish" the opportunity to help and wished me a "blessed" day!

Click for larger image

Almost all the hardware fixes on the net involved completely resoldering the four copper coils, which I did by first removing them from their silicone rubber bed and then resoldering them back in position. This didn’t work and without access to another f1703 monitor to compare voltages, I can only conclude that it is probably something to do with the processor board switching the inverters off.

I don’t have a circuit either and so have been left in a rather frustrating cleft stick – at least for the time being.

Similarly, Apple has had problems with their Studio Display 17-inch monitors (M7649). The symptoms with these are uneven dull pictures and the power light flashing.

Once again it is the inverter board that is the problem but the modified replacement (V041063.00M3S by MoniServ) costs US$110 plus freight.

Why can’t these companies offer free circuit diagrams with detailed information on how to repair or modify these products once they are out of warranty? If an owner doesn’t have the technical ability to do the repairs, at least he can supply the information to someone who is competent to do the work. Wishing people a blessed day doesn’t quite cut it.

Grundig TV set

I was asked to do a service call on a Grundig ST84-796-9 TOP LOG (CUC 6380 chassis) TV set. I don’t normally do service calls but I made an exception in this case. This large 80cm CRT TV was located in a home unit and was simply too heavy to lift and take to the workshop.

I was asked to phone before I arrived at the block of units because of their secure internal parking arrangements. When I arrived, it wasn’t hard to see why – the location was right in the middle of a large shopping centre with no on-street parking.

Once inside the unit, I was surprised at how quiet and secluded it was despite its location. I was also filled with dismay when I realised the set was situated in one of those much-dreaded entertainment cabinets, with very little access.

The problem was no sound which is an unusual fault these days. Fortunately, I could see the cause as soon as I got close to the TV.

What happened was that the mains power on/off switch had been giving trouble and wouldn’t latch in the on position. So, to keep the set on, the owner had jammed a match splinter in the side of the on/off button.

Unfortunately, he didn’t realise that this switch also has a momentary switch built in. This normally re-
sets the microprocessor and mutes the sound to prevent unnecessary noises when switching the set on or off.

I proved the point by removing the match and pushing the switch in far enough for the set to come on then releasing it slightly so that the momentary switch was no longer on. This brought the sound on with the picture.

I told the client that I would have to order the switch in from Grundig and it would take time. In the event, the switch (part no. 297032917200) was no longer available but as luck would have it, I did have a 297032917204 switch in stock.

Back at the customer’s unit, I managed to rotate the set in the entertainment cabinet and remove the back and the main chassis. I then had to remove the control and display chassis to gain access to the switch. Finally, I removed the whole assembly and examined it carefully.

It was indeed a very special switch with a solenoid built in. It had three functions – On, Standby and Full Off – which could be controlled by the remote. You only had to push the switch in to go into either the full On or Standby modes which are controlled by the remote. If you pressed the remote’s Off button once, it would go to Standby. If you pressed it twice, it would pop the switch out to Off using the solenoid.

The original switch looked identical to the one I had (thank goodness) but it also looked as though there was nothing wrong with it as it was now latching properly every time outside the cabinet.

What was crook was the power on/off button itself which had cracked and so was not sitting on the switch properly. Once again I was left with a dilemma. The faulty knob would probably work perfectly well super-glued to its original switch. However I could only go down that path once. The knob was no longer available and once superglued on, you would never be able to remove it if the switch failed.

In the end, I decided to replace the switch just to make sure and super-glued the knob onto it. This fully restored the sound and it was a win-win situation all around.

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