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SERVICEMAN'S LOG Two VCRs, a TV & a computer Amongst the many services we offer nowadays, one is upgrading computers. This always sounds straightforward but it is easy to get caught with unforeseen problems. But first, a few of my more regular VCR and TV problems. The very nervous man who waltzed carefully into the shop was gently cradling his Panasonic video. “What’s it likely to cost?”, he whispered. “Well that depends on what’s actually wrong with it. What’s it not 28  Silicon Chip doing properly?”, I enquired. I tried to sound matter-of-fact so as not to frighten him too quickly. Mr Nervous fished around in his pocket and finally produced a small bit of folded paper which he passed to me. On it, he had written, in small neat writing, a short list of symptoms with the problems outlined very precisely. Summarising it, his Panasonic NV-G30 VCR was showing a noisy picture on playback and he could only tune in a channel if the antenna was plugged directly into his TV. He couldn’t watch TV whilst recording another channel. Oh dear, I thought, this could be a tricky one and the age of the video meant it wasn’t too far from its use-bydate. If, as I suspected, it was the RF modulator, this poor bloke could die from a coronary when told the likely cost. After all, the cost was obviously at the forefront of his mind. But then again, maybe he had misinterpreted the symptoms or perhaps it was only a dry joint. Who could tell? I decided the best course of action would be to come clean and tell him all the options and their likely cost, and hope he wouldn’t collapse on the floor. He was slightly taken aback with the worst option but he only wobbled and didn’t quite fall over. We finally settled on spending an hour’s labour on the machine to see what I could come up with. He made it to the door and I hoped he would make it all the way home. That afternoon when the bench was clear, I hooked up the video and switched on. My worst fears were confirmed – the symp­toms were precisely as listed, there were no intermittent dry joints, and the heads weren’t dirty. Obviously, the output from the video was low in gain, especially in the E-E mode (Electronic to Electronic mode or Tuner/RF modes). I stripped the unit down and removed the RF modulator which took quite a bit of effort. I then removed the covers and exam­ined the whole assembly carefully under a magnifying lamp. I could­ n’t discern any cracks, dry joints or obvious burn marks (of course, that just might be my age and sight) so, to be on the safe side, I reworked all the solder joints, reassembled the unit and switched it on. Unfortunately, that made no difference so it was back to the drawing board. Because the VCR is closest to the antenna, which is after all a near perfect lightning conductor, I considered that it might have suffered a small strike in a storm – enough to blow out the semiconductors in the front end while leaving everything else intact. With this in mind, my next step was to check all the diodes in the modulator. The multimeter unfortunately did not yield any secrets. I also measured the B+ to the modulator and checked the VTR/Antenna switch line but all was correct. At that point, I figured that I had gone as far as I could and that the worst-case scenario of a new modulator was inevi­ table. However, I decided to put the unit to one side for the rest of the day until I could gather the heart to break the bad news to Mr Nervous. And then came a stroke of luck. Later that afternoon, I got a call from a colleague wanting some technical support on a TV set he was working on. Fortunately, I was able to help him with his problem and then, because he is something of a National Pana­ sonic expert, I thought I would run my own problem past him in exchange. “Oh yeah, I know what your problem is – I thought everyone knew that symptom and its cure”. Obviously, everyone bar my humble self, that is. “It’s Q51, a 2SC2570 – just change it. You can’t measure it, apparently it’s gain changes”. My mind instantly went back to my college days when my tutor insisted that it wasn’t possible for a transistor to do this. “Er, thank you, of course I knew that – it just temporarily slipped my mind”. I couldn’t wait to test this wellknown cure. As it hap­pened, he was absolutely right on all counts. It was the transis­tor and I couldn’t measure anything untoward about it on the multimeter. And the VCR now worked perfectly. Anyway, I was certainly grateful to him, especially as it meant that Mr Nervous wouldn’t pass out at my counter. A Panasonic morning It must have been Panasonic day because the next job dropped in after Mr Nervous was yet another Pana­sonic VCR. The young man who came in was a completely different character from Mr Nervous and the NVL20A he was carrying was completely dead. And, he added, “it wasn’t just the fuse” because he had had a look at it and it was OK. I wasn’t too happy on learning that it wasn’t “just the fuse” because it meant that the young man had dismantled the switchmode power supply in order to gain access to it. Anyway, when I later I retraced his steps, I found that 240V was definitely going in and that +350V was appearing across the main electrolytic filter capacitor and was being applied to the switching IC. The power supply wasn’t making any noises at all but just to confirm that there were no shorts on the second­ary, I checked all the diodes using a multimeter to ground. Either the switching IC had carked it or the start-up circuitry wasn’t working. I considered the latter to be the more likely and concentrated on the electrolytics around the IC. C109 is a dirty grey/brown unit rated at 1µF 400V 105°C and it was definitely looking suspicious. I replaced it, reconnected everything, switched on and stood back. Nothing went bang and after one or two seconds I was rewarded with the clock display flashing and when I pressed the power button, everything sprang to life. Before putting it all back together, I carefully examined the rest of the electros in the power supply but they all looked pretty good. I boxed it up and soak tested it before phoning the young man to tell him the good news. I only wish all my jobs were that easy. The crook Blaupunkt Just before closing time, there was a lot of activity in shop as a large family tried to herd in their TV and plonk May 1997  29 it down on the counter. The story I pieced together from their various accounts, given in unison, was that a relative had given them the set and it wasn’t working. The set was a 56cm Blau­punkt Malta IP32 stereo TV in a wooden veneer cabinet. It looked in good condition but it made me nervous because it was a foreign TV and was over 10 years old. I identified the ringleader of this family fairly quickly because he was older and taller than the rest. When I mentioned problems about spare parts, their cost and availability, he was a little crestfallen as they were all so obviously proud of their new acquisition. And when one of them 30  Silicon Chip pointed out that one of my stickers was on the back (dated, I might add, in 1990), I felt honour-bound to at least have a look at it, which I agreed to do the next day. Before I removed the back, I looked up the last time I had serviced the set to find that the previous owner had lived very near the sea and I had replaced the flyback transformer seven years ago. When the back was un­clipped, I realised my worst fears because virtually all the metal surfaces were heavily rusted and parts of the PC board pattern had turned green. I gingerly connected the power and switched it on with the remote control. There were a few minor sparks as it tried to fire up but it didn’t quite make it, although the sound appeared to be working. Fortunately, when I had repaired it the last time, I had purchased the service manual for it. Now I was perusing the circuit for only the second time. Had it really been worth spend­ing all that money to store this manual for seven years? I wasn’t really sure but at least I had it for this job. Anyway, with the aid of the circuit diagram, I was able to identify and measure all the B+ rails. These were all OK, even to the collector of the line output transistor (V830). Next, I connected a CRO to the collector of this tran­sistor and switch­ed the set on. There was a brief flash of activ­ity on the screen before the trace went flat. More to the point, I could smell and see sparks everywhere. My immediate conclusion was that this was a very corroded old TV and that the EHT protection circuit was operating. And this in turn was preventing the line oscillator from delivering a signal to the output stages. Before going further, the set obviously had to be cleaned up. As a result, I sprayed, wiped and cleaned all the EHT stages with CRC2-26, including the ultor cap, the tube socket, the flyback transformer and the focus pot. After making sure that I had removed all the excess, I then heated all these parts with a hairdryer to make sure they were dry. When I switched on this time, there were no more sparks but still no EHT. It was time to go over the EHT protection circuit. A quick glance at the circuit soon established that the protection circuit is based on IC W700 and transistors V802 and V799. I overrode it by shorting pin 7 of W700 to ground and tried again. This time, smoke gushed from the flyback transformer and the job was starting to look expensive. Just in case something was loading it down, I disconnected the CRT ultor cap and also the CRT socket but there was still smoke. Finally, I disconnected the focus pot. This time there was a corona discharge from the flyback transformer to its nearest components so we had EHT. On examining the focus control, I could see that a carbon track had been etched on the board. Ob­viously, it had been arcing over for quite some time before it finally gave up. I cut, cleaned and filed this track away to stop the arcing but when it was all reconnected, smoke again erupted from the flyback transformer and, to a lesser extent, from the focus pot. I knew it was hopeless to try any more – these parts just had to be replaced. I phoned the agents in Melbourne to find that both parts were still available, although they were pretty expensive. I could only pass the news on to the family and advise them that I really didn’t think the set warranted this expense. Surprisingly, they didn’t agree with me. I suppose that because they got the set for free, my service cost really only represent­ ed the full purchase price to them. As a result, they decided to proceed and so the parts were ordered. The parts arrived about a week later and I quickly set about installing them. When I removed the old focus pot, a plas­tic clip on the case came off, the ceramic element fell out and I could see where it had been burning internally. I cleaned the PC board where the two parts had been located before soldering in the new ones. When I subsequently switched it on, I was rewarded with a blurred picture. This came good when the focus control was ad­ justed. I then checked all the functions and left it on to soak test. Despite its years, the picture was excellent and, after a couple of days, I felt confident that the set was going well. However, when the family clan reassembled to collect it, I told them that the set was old and corroded and that I could only guarantee the parts and labour I had supplied. I don’t know whether this sank in but I haven’t heard from them since. The computer upgrade No sooner had they departed than Mrs Brown brought in her son’s old 286 and wanted it upgraded. Despite his pathetic pleas for a new Pentium machine with all the bells and whistles, Mrs Brown was on a budget and after some heavy haggling settled for a secondhand 486 motherboard with 8Mb of RAM, a 1Gb IDE hard disc drive, and a new Microsoft mouse. She also supplied the upgraded software that was to be installed, namely DOS 6.22 and Windows 3.11. I allowed an hour’s labour to swap the hardware plus a further hour to load the software and quoted accordingly. All went well apart from the usual swearing and bad temper that goes with removing and fitting a new motherboard in under the power supply and drive bays. The other drama involves working out where to connect the leads from the front control panel and configuring the turbo speed display. It’s OK if you have a manual for the motherboard but in this case the manual had long ago disappeared. Anyway, the new 486 booted up OK and I was able to install DOS and Windows without any dramas. I then ran Memmaker to opti­mise the RAM and configured Windows for 32-bit file and disk access. I also set up a permanent swapfile, to ensure efficient operation. Altogether, it was a fairly satisfactory job even if it did take longer than expected. It’s amazing how the time disappears when working on a computer. The new mouse was a beauty and felt very positive. I installed MOUSE.EXE v. 9.01 through the usual setup disk and configured it as described in the manual. A secondhand pup? I was happy with the job and more importantly so was Mrs Brown and her son when I showed it to them. That is, until about a week later when they reappeared in the shop with a completely different attitude, namely that I had sold them a secondhand pup. After soothing down their ruffled feathers and reassuring them that it was all guaranteed, I finally got down to asking them what the real problem was Despite all the aspirations of the upgrade being an essen­ tial educational tool, it turned out that an old game now refused to work and the computer was hanging when he tried to get into it. “Look”, I said recklessly, “leave it with me and I will fix it”. Courageous but foolish words. That night, I set it all up and tried to figure out what was going wrong. The game was Battle Chess, circa 1988. This is a mouse-driven animatMay 1997  31 ed 3D game of chess. The graphics of this par­ticular version are now quite ordinary by modern day standards but it is still an excellent game and the fault was exactly as described. The easiest answer would have been to get an upgrade of the game but in the light of my rash promise, this was no longer an option. OK, so it worked all right on the old 286 but not since the upgrade, so what was it that it didn’t like? Was it the speed of the new machine, the graphics, a memory conflict, or something else? First, I checked the amount of free RAM by typing mem /c/p. This gave the largest executable program size as 613Kb, which was plenty. But was there perhaps an EMM386.EXE exclusion conflict in high memory? I re­boot­ed the computer, pressed F8 when it reached “Starting MS-DOS”, and said no to both the HIMEM.SYS and EMM386.EXE lines in the CONFIG.SYS file. This meant that every­ 32  Silicon Chip thing would be loaded low. When the bootup sequence was complete, I ran mem /c/p again and this reported that the largest executable program size was now only 530Kb. Was this too low to run this program? There was only one way to find out. When I typed C:\CHESS>CHESS, the opening screen came up as usual and when I pressed ENTER to start the game it hung just as before. And as before, the edge of the mouse was just visible on the righthand side of the screen. Strictly speaking, it wasn’t completely “hung” up in that the CAPS LOCK, NUM LOCK and SCROLL LOCK keys still functioned. However, no other keyboard or mouse commands made any difference apart from the three-fingered salute “ CTRL-ALTDEL”. By now, I was fairly sure that it wasn’t a memory conflict. Perhaps it was the faster motherboard or perhaps it was the driver for the hard disc. To test the latter theory, I decided to copy the Battle Chess program to a bootable floppy disc and try running it from there. This time, when the second ENTER was depressed, the game didn’t hang and instead one of the squares was flashing as if to start. The only problem was that there was no mouse; I had for­ gotten to load the driver. However, I quickly discovered that the game could be played using the keyboard, although I didn’t know all the commands. I did find, however, that the arrow keys and ENTER moved the pieces, while F1 brought down the menu bar. So the game worked OK when loaded from a floppy disc with­out the mouse. The fact that it was being loaded from a floppy disc was probably irrelevant; instead, I was beginning to suspect a rodent problem. To prove this point, I copied the mouse driver from the hard disc to the floppy, loaded it and tried loading the Battle Chess program again. This time, the game hung as before but I was getting closer. It seemed to me that the game didn’t like the new mouse on COM1. I tried plugging the mouse into the second COM port and even tried a different type of mouse before I realised that it wasn’t the mouse itself that it didn’t like but its driver (MOUSE.EXE). I was surprised at this turn of events because I have always found the Microsoft mouse to be excellent, with very few compatibility problems. Unfortunately, this particular driver wasn’t compatible with this early version of Battle Chess. So, what was the fix? I decided that the only course was to experiment with some older drivers. My first choice was another Microsoft Mouse driv­ e r, MOUSE. COM v8.2. I deleted MOUSE.EXE from the floppy disc and replaced it with MOUSE.COM (at this stage, I was sticking with the floppy disc to avoid any other unforeseen conflicts). This time, everything worked correctly. The Battle Chess game loaded without problems and the game could be played using the mouse. My next step was to see what could be done on the hard disc. Normally, when booted, MOUSE.EXE v9.01 is mainly loaded into high memory (272 bytes into conventional memory and <at>echo off cls mouse.exe off cd\chess lh mouse.com chess.exe mouse.com off cd \ lh mouse.exe I put the old mouse driver in the chess directory, so that it would be found when the time came to load it. Basically, the batch file cleans up the screen, turns off the MOUSE v9.01 driv­er, switches to the chess directory, loads the compatible MOUSE v8.2 driver, and starts the game. Then, when you quit Battle Chess, it turns off the old mouse driver, switches to the root directory and loads the new mouse driver. It all worked, so I left it at that. When Mrs Brown picked up the computer the next day, I pointed out that there was nothing really wrong with it. Instead, the problem was a software conflict that could have been fixed by upgrading to the latest version of Battle Chess. I think she might have suspected something like that all along, judging by the slightly detectable smirk on her lips as she and her boy disappeared out to the car. Or perhaps I’m becom­ ing oversensitive. Just in case you’re wondering, the above batch file will only work at DOS level. You cannot change mouse drivers within Windows without a lot more work. I have also been informed that Battle Chess was upgraded in 1992/1993 and was last available on CD with terrific new multimedia and VGA graphics. I don’t know whether it is still available but apparently this version worked fine with MOUSE. SC EXE v9.01. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my Bankcard   ❏ Visa Card   ❏ MasterCard ❏ Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ 24,336 into upper memory). I didn’t really want to stop using this driver as it worked so well in Windows. Fortunately, when I typed MOUSE/?, a whole host of options appeared, one of which was “off”. To save time and because I wasn’t actually making any money on this software problem (which wasn’t really my responsibility), I decided to write a simple batch file. This file, called CHESS.BAT, swaps the mouse drivers around as necessary and loads the game. This batch file went like this: May 1997  33