TideLog Archive for the “Electronics” Category

This is another wear related symptom, and often occurs on power down of an old system after a power cut. It is again to do with the input regulation circuit (the main resistor, diodes, and rectifier transistors bolted to the keypad chassis). If your Optima starts OK on battery, but not on just the mains, the cause of this is the CPU isn’t getting enough power to start up from the AC to DC rectification stage. The start sequence goes visually like this:

  1. Power is applied, the regulators get up to working voltage, and start supplying power to the CPU.
  2. The LED’s all come on, briefly, as the CPU boots up, doing its self test of itself, and the NVRAM, containing your code and exit/entry timers.
  3. Within a few milliseconds of 2 above, once the CPU has started, the LED’s go out, and the alarm now goes into a full alarm condition, leaving just the Power LED on, and any open Zone LED’s. If no zones are open, just the power LED is on.

If the LED’s all stay on with no more activity or sound, the CPU isn’t starting correctly, because the voltage to it is insufficient coming from the AC to DC rectifier stage. Allowing the alarm to start here going into full alarm, would cause too much current inrush, and voltage drop to sustain keeping itself running, due to the strobe/bell and 13v PIR’s drawing power when there isn’t enough.

The transformer puts out 16.2v AC. If the voltage at your battery charge terminals with no battery connected is less than 14v, (the last one I did was 10v) the whole system is being starved of power. The two transistors that are bolted through the keypad chassis need to be replaced, the big three-legged things top right of this picture with the holes through the tags:

Optima-XM-board-faulty-regulators

I always replace both to make sure, as they can be quite stressed out at such an old age, and be breaking down under load, as does the 47 ohm battery resistor. I also check the capacitors accompanying them. The leftmost transistor is a Toshiba TA7805S Positive Voltage Regulator which seems to be the battery regulator, I’ve uploaded the datasheet to Tidelog HERE. The second (rightmost) transistor is an ST Microelectronics LT8I5CV, for which I cannot find a datasheet, and I assume is the AC rectifier stage’s main DC regulator.

I am attempting to find suitable modern equivalents for these regulators, so if any electronics guys out there can help, I’d be most grateful, as finding info on these 15+ year old components is tricky! I’m running out of working ones to cannibalize off old unrepairable Optima boards! A good alternative to the Toshiba TA7805S is the Panasonic AN7805F, the datasheet is on TideLog, HERE, for you to take a peek at, if you understand electronics 🙂

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I’ve had this problem a few times on my laptop. It occurs mostly when the power suddenly goes off and it switches to battery. You lose all capacity monitoring, and can’t tell how much is left. The system tray icon changes to this:

no battery detected

Microsoft’s forums are hilarious. Their “Most Valuable Professionals” give the funniest canned cut ‘n’ paste responses, from, “Your power driver is corrupt” to your “Windows needs reinstalling!”. I know exactly what causes it, and it ain’t anything to do with “power drivers” or corrupt Windows. It’s the little monitoring chip in the battery. Like a lot of integrated electronics, it sometimes gets confused. Sudden switchovers from mains to battery tend to cause it, especially if there’s any surges from the battery as it kicks in.

The age old advice of “Reboot!” is the wise advice. If that doesn’t cure it, turn your machine off, remove the mains and battery, and hold your power button down to discharge the circuitry in your device (apart from the RTC circuit, but this doesn’t matter), that should cure it. Removing the battery opens the circuit to the sensing system in the battery, and resets it.

Simples. I hate MVP’s, they go on a 5 day course and think that gives them a Professional title? I’ve done MVP courses, but have the skills and years of software and electrical experience to further and back them up

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I previously posted about the rise in the occurrence of the Optima XM series main regulator resistor blowing. I’ve since had a few boards sent to me for repair, and a few users have also asked me about the resistor colour band codes. Below is my image of what an Optima XM & XM6 resistor SHOULD look like, before it burns up and scorches the board:

OptimaXM-and-XM6-resistor-undamaged

For those who want to know the resistance, the colour bands are the following: Gold, Black, Purple and Yellow, with a space between the gold and black bands. Here’s a diagram I made that shows how to interpret them:

resistor-color-code-allWhen working out the resistance of a pass-through resistor, you start by having the closest-together bands on the left. The resistor in the Optima is a 4 band one, so the resistance is worked out like so:

1. The first band is the Yellow one, which is 4;

2. The 2nd band is Purple, which is 7;

3. The 3rd is the Multiplier, which is Black at 1. The multiplier simply tells you how to multiply the first two values. Any multiplier with a K next to it is kilo (thousands, and the ones with M are Mega. So if our value of 47 was to be multiplied by 1k, a thousand, the value would now be 47,000. The Optima’s is simply a 1 multiplier, so it stays at 47, as you can’t divide it by 1.

4. We jump straight to the Tolerance band, which is Gold, at ±5%. The Tolerance band simply denotes how precise the manufacturing process of the resistor was, they can be 5%, 10% or 20%

Your total resistance is 4 + 7 * 1 = 47 Ohms ± 5%. Do not confuse it with a 47K resistor, it is 47 ohms, not 47,000 ohms, a K after the value indicates thousands.

Note that surface mount resistors and fuses do not have bands, they have the values stamped directly on them. If you are replacing a burnt resistor, clean the board around it with vinegar or contact cleaner to remove the burn marks. 99% of the time I’ve never had any actual board or trace damage, they are just burn marks from the resistor coating. You can use the methodology above for all the other resistors on the board, too, as they are mostly 4 band ones. If you are in any doubt I can do your repair for you, as I can repair traces and board damage professionally, use my contact form on the left sidebar to get in touch with me.

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Bad sectors are little clusters of data on your hard disk that cannot be read. More than that, though, they have the potential to cause real damage to your hard drive (catastrophic failure) if they build up over time, stressing your hard drive’s arm, which contains the read/write head, there are two for each platter, one for each side. Bad sectors are fairly common with normal computer use and the imperfections of the world we live in. Like chip fabrication and LCD panel manufacturing, HDD manufacture is a very critical, precise process, and like a TFT with bad pixels from the factory, you do get bad sectors with a HDD due to imperfections when it’s made. The manufacturers make legal allowances for a certain limit to these imperfections before warranty claims can be made, like the legal limit of 5 dead pixels on a TFT. However, there are several simple steps you can take to prevent HDD bad sectors and to repair any that you do have. Having bad sectors will slow down computer performance as well, as your drive takes time attempting to read them. Here is a step-by-step guide. The most common questions I get as a computer engineer are “What is a sector?”, and “How are HDD bad sectors created?”

A sector is simply a unit of information stored on your hard disk. Rather than being a mass of fluid information, your hard disk stores things neatly into “sectors”, a bit like us humans putting things into boxes, and the box only holds so much, and all boxes are the same size. The standard sector size is 512 bytes.

There are various problems that can cause HDD bad sectors:

  • Improper shutdown of Windows, especially power loss while the HDD is writing data;
  • Defects of the hard disk, including general surface wear, pollution of the air inside the unit due to a dirty or clogged air filter, or the head touching the surface of the disk;
  • Other poor quality or aging hardware, including dodgy data cables, an overheated hard drive, and even a power supply problem, if your drive’s power is erratic;
  • Malware.

Hard and soft bad sectors

There are two types of bad sectors – hard and soft.

Hard bad sectors are the ones that are physically damaged (that can happen because of a head crash if your drive is dropped while running and writing data), or in a fixed magnetic state. If your computer is bumped while the hard disk is writing data, is exposed to extreme heat, or simply has a faulty mechanical part that is allowing the head to contact the disk surface, a “hard bad sector” might be created. Hard bad sectors cannot be repaired, but they can be prevented. The heads of a hard drive float on the air cushion generated by the platters spinning, they fly less than the width of a human hair away from the platters, even a small speck of dust is like a mountain, so knocks are definitely to be avoided.

Soft bad sectors occur when an error correction code (ECC) found in the sector does not match the content of the sector. Whenever a file is written to a sector, the drive calculates a “checksum”, which is used to verify the data, if it doesn’t match upon read, the drive knows the sector is weak. A soft bad sector is sometimes explained as the “hard drive formatting wearing out”, in other words the magnetic field is weakening, like an old video cassette – they are logical errors, not physical damage ones. These are repairable by overwriting everything on the disk with zeros. Like tapes and CD’s, the magnetic surface on a hard disk is not infinite, it is affected by other magnetic fields around it, so data recovery guys like me recommend regularly imaging a drive directly to another, frequently, to keep the data fresh and readable.

Preventing bad sectors

You can help prevent bad sectors (always better than trying to repair them, as they say prevention is better than cure!) by paying attention to both the hardware and the software on your computer.

Preventing bad sectors caused by hardware:

  • Make sure your computer is kept cool and dust free;
  • Make sure you buy good quality hardware from respected brands. Cheap RAM and power supplies are my biggest culprits from experience;
  • Always move your computer carefully, and make sure it is TURNED OFF, not in Sleep mode, it can wake up while being moved, especially a laptop;
  • Keep your data cables as short as possible;
  • Always shut down your computer correctly – use an uninterrupted power supply if your house is prone to blackouts.

Preventing bad sectors using software

  • Use a quality disk defragmenter program with automated scheduling to help prevent head crashes (head crashes can create hard bad sectors). Disk defragmentation reduces hard drive wear and tear, thus prolonging its lifetime and preventing bad sectors;
  • Run a quality anti-virus and anti-malware software and keep the programs updated.

Monitoring bad sectors

If you use a tool like HD Sentinel, or CrystalDiskInfo, and you notice bad sectors on your drive, keep an eye on it. A few sectors bad is not normally a problem, as I mentioned at the start of the article, up to 5 bad pixels on a new TFT is allowed before it becomes a warranty claim, hard drives are allowed a few bad sectors due to the imperfections of their manufacturing process. They are manufactured with what are known as “reserved sectors”, a spare area of the disk only accessible by the controller board. If a sector is weak, the controller will attempt to move the data to the reserved area, if this is successful it then attempts a quick read/write test on the old sector (takes less than a few milliseconds), if it fails it marks it as bad in the sector map, also stored in the drive reserved area, along with drive firmware, so that it doesn’t attempt to use it again.

If the number of bad sectors starts increasing, or you start to experience other symptoms, such as the drive dropping out completely as if you unplugged it, or any clicking, and data taking longer to read or copy, this could indicate a fault with the read/write heads, or the control circuitry. Stop using it immediately and back up any important data to another drive. If the failing drive is under warranty, print a log off from HD Sentinel and take it along with you to return the drive, as evidence.

S.M.A.R.T Values to look for

When looking at S.M.A.R.T (Smart Monitoring And Reporting Tool) analysis, the two main areas to look out for are:

Reallocated Sector Count

This shows how many of the drive’s Reserved sectors have been used. If too many of these are used it generally indicates a problem with the disk surface.

Current Pending Sector

This shows how many bad sectors are currently pending a rewrite. A hard drive will always try to rewrite the sector, if it fails, the sector is reallocated into the reserved, the drive adds the sector on to the Reallocated Sector Count, and the original sector is then marked as unusable. If the rewrite is successful, the Pending Sector count will drop.

 

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Western Digital make really good hard drives, but where their Elements, Passport and MyBook drives are concerned, they’ve taken a wrong turn. The 2.5″ versions all have proprietary PCB’s on the drives themselves, so there’s no standard micro SATA data and power connectors like you’d expect. The USB connector and LED, plus the interface controller, are on the single board as well! This means you can’t just take the drive out and connect it to another USB to SATA enclosure.

A lot of very modern WD Elements, MyBook and Passport enclosures are now also encrypted, meaning the data can only be accessed when the control board is functioning correctly. In this article I’ll show you how to recover data from a WD Passport (laptop sized drive) enclosure, if the USB connector gets damaged.

1. Disassemble the enclosure, remove the drive, then remove the PCB from the bottom of the drive using a Torx screwdriver.

2. Flip the drive board over, you’ll see the following capacitors. Remove them using a soldering iron or a heatgun, being careful not to overheat or damage anything:

usb-only-western-digital-drive-capacitors

3. Next you need to take a standard SATA connector from another drive, or from a parts supplier (eBay has them in droves, search for COMAX SATA connector). Once you have it, take a look at it, you’ll see long pins and short pins. All the long ones are GROUND pins:

sata-connector-ground-pins

4. From the back side of the PCB (the componentless side which faces away from the drive when fitted), you will see pins E71, E72, E73 and E74, these belong to the SATA data pins. The other four pins marked with a red square belong to ground pins:

usb-only-western-digital-drive-E-pins

5. Now solder everything together, using this pinout:

E71 – Tx+
E72 – Tx-
E73 – Rx-
E74 – Rx+

The SATA standard uses two lines, a positive and negative, for Data TX (Transmit), and two for Data RX (Recieve), each having a separate ground on the ground lines. Use my picture below as a wiring reference:

usb-only-western-digital-drive-finished-wiring

Now all you need to do is use a standard USB cable to power the drive (if your connector is broken you can try soldering the power lines of a USB cable to the port power pins), connect via SATA to your PC, and it should work. NOTE: This WILL NOT work if your drive uses encryption, as that runs through the USB data lines, because we’re bypassing it, it won’t work.

You may get some “USB device not recognized” errors. Try connecting the SATA drive to a SATA hotplug port, connecting the data cable first, then the power, once Windows has started. Hotplug ports are usually purple or orange, it depends on the board manufacturer, Gigabytes are purple.

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