Replacing a bad timing crystal
What's this all about?
There have been reports of MG-350HDs going "bad" -- certainly, the one on which this page is based needed some surgery.
This step-by-step guide should do one of two things:
- tell you how to fix your own MG-350HD if it's having the same problems
- convince you that you shouldn't be mucking about with soldering surface-mount components, and should just return the unit for a warranty exchange
Disclaimer
This procedure will void any warranty remaining on your MG-350HD.
You should not attempt this procedure if you do not have:
- experience soldering surface-mount components
- tools for soldering surface-mount components (a plumbers soldering iron does not count)
- very steady hands
- an MG-350HD that already needs this fix, on which the warranty has either run out or already been voided by some other modification
- a willingness to throw your MG-350HD in the garbage bin if you wreck it following these steps.
To be completely specific:
There is no warranty expressed or implied in documenting these steps. If you choose to follow them you do so at your own risk.
An Overview of the Problem
Every digital circuit uses a timing signal to synchronise its operations. Different processors and chips might use different frequency signals -- for example, the CPU in a (relatively) modern PC might be clocked at 2GHz (that's gigahertz, or 2 billion "ticks" per second). The processor in the MG-350HD uses a 27MHz signal.
The signal is generated by a crystal oscillator -- a very precisely shaped piece of quartz crystal tuned to vibrate 27,000,000 times per second when excited by an electric current.
It seems that some units might have crystals that are borderline in their stability -- that is, after a while they might start having problems keeping that 27MHz rate going. When that happens, the clock signal that's telling the processor when to do things goes away, and you get random strange resets or the Green Screen of Death.
How To Tell If You Have This Problem
If your unit resets itself randomly (most likely when under load -- playing back video or music) and/or suffers the Green Screen of Death (you'll know it if you have it), then you might have this problem. These steps will help you narrow down whether it's this or something else.
The first symptom to look for is a gradual breakdown in the picture, either when playing video or when just looking at the menu screen. This will most likely appear as "crackly lines" across the screen, gradually getting worse until the screen becomes unreadable, or your TV/monitor refuses to sync to the signal any more, and/or the unit crashes -- possibly resetting to try again, possibly not.
If this is the case, try this:
- Stand the unit upright if it isn't already (if you have a hard drive in it, it should be upright anyway for cooling purposes -- these things run hot)
- With the unit running and playing something on screen, wait for the picture to start to break down. When it's just beginning, move your hand to the side of the unit away from the hard drive -- ie the side with the circuit board against it.
- If the picture gets worse (even marginally), or the unit resets itself, or anything else unexpected happens, you can be reasonably certain you have this problem.
To confirm further, you'll have to void your warranty. See below for instructions.
What You Need To Fix It
Abilities
- Experience soldering surface mount components. There are a lot of tutorials on hand-soldering surface mount components out there, and Google is your friend for finding them. Practice on something else first -- something that you don't mind breaking.
- Steady hands. These components are Small.
- Patience.
Tools
- Electronics soldering iron with a very fine point.
- Solder removal braid or wick (a mechanical solder sucker won't cut it here)
- side cutters
- good lighting
- a magnifying glass/illuminated magnifier/third hand type base with a magnifier on it
- #2 point phillips head screwdriver
- tweezers
- electrical tape
- multimeter/continuity tester
Components
- a 27MHz crystal -- surface mount or through hole, doesn't matter
- 2 pieces of Kynar or similar wire (also known as "wire wrap" wire)
- fine solder
How To Do It
Warning -- static electricity kills! (some electronic components)
You will be working with components that are static sensitive -- this means you can fry your unit or the crystal via static discharge. Work in a static-safe location, and ground yourself before touching the board or any components.
All the voltages on the motherboard are safe for humans. You could lick the board while it was running and it'd probably crash, but not hurt you unless you count ingesting toxic chemicals as "being hurt". Sissy.
Preparing to remove the motherboard
- Remove the thumbscrews holding the hard drive cover, and remove the cover.
-
Unplug any hard drive installed, unscrew its mounting plate, and remove it. Set aside in an anti-static bag.
Image 1 (click to enlarge): Shows the location of the 3 drive plate screws.
The hacked-in console port connector and board is visible at the top.
- Very carefully unplug the ribbon cable connecting the front panel to the motherboard. Using gentle pressure, pull the cable straight up.
Image 2 (click to enlarge): Shows the location of the front panel connector (left of image)
and S-Video daughterboard connector (top right).
Also highlighted is the blob of hot melt glue that holds the antenna cable down on the motherboard.
- Unscrew the thumbscrew from the bottom of the front panel
- Gently remove the front panel and set aside in a static-safe location
- Carefully unplug the S-Video, Composite video, and optical audio connector daughterboard in the same manner
- Remove the 2 small black screws from the rear panel that hold the daughterboard in place; remove the daughterboard and place it in a static-safe location.
Image 3 (click to enlarge): Shows the location of the 2 screws that hold the S-Video, composite,
and optical audio out daughterboard.
- Disconnect the wireless antenna connector from the WiFi card -- using gentle pressure (a fingernail is enough), just lever it straight up and it should pop off.
- There is a blob of hot-melt glue holding the antenna cable to the motherboard (see image 2). Gently slide the antenna cable through the glue (it shouldn't be stuck, or at least not firmly) so that you have as much slack in the cable as possible between the glue and the rear panel
- Unscrew the antenna cable from the rear panel. You'll have to unscrew the connector on the inside as far as possible, then push it back through the rear panel to free the nut that actually holds the connector in place. This will twist the antenna cable, which is why you want as much slack as possible to spread the twist along the cable and minimise the risk of any damage to the cable.
Removing the WiFi card
The card is held in place by 2 spring tabs, one on each side. They are soldered to the card, probably to prevent any bumps from jarring them loose.
- Using your soldering iron and the desoldering wick, remove most of the solder blobs from the spring tabs. If you get it all at this step, the spring tabs will be free of the WiFi card.
- You might have to exert gentle pressure outwards on one spring tab with something that won't scratch or damage any components -- the eraser end of a pencil works well -- while heating any remaining solder. Once the spring tab pops free, do the same with the other tab
- Push both tabs away from the WiFi card to release it; it pivots upwards to about 15 degrees from horizontal, hinged by the Mini-PCI connector itself. Gently pull it straight back (not up!!) out of the connector, and set it aside in a static safe location
Image 4 (click to enlarge): Shows the location of the two soldered tabs that hold the MiniPCI card in place.
Also shown (in yellow) is the Reset switch, only accessible by opening the case.
Image 5 (click to enlarge): Shows the Ralink MiniPCI WiFi card.
Note the two antenna connectors at the top right; only one is used for the MG-350HD
Removing the motherboard
- Remove the 2 small black screws in the rear panel that hold on the Component, Stereo L/R, and Coax digital connectors.
Image 6 (click to enlarge): Shows the location of the two screws holding the component,
Stereo and coax audio out connector block in place.
Also visible is the hacked-in console port connector (top left)
- Remove the 2 small black screws holding down the motherboard. One of these is under the WiFi card, hence the need to remove it (above)
Image 7 (click to enlarge): Shows the SVideo daughterboard connector (yellow), front panel connector (purple),
and the two screws that hold down the motherboard (red).
- Gently wiggle the motherboard free of the case, lift it out and set it down in a static safe location.
Verifying the problem
- With the motherboard free of the case, reconnect the front panel and the S-Video/component daughterboard. Be careful pushing the ribbon connectors into the motherboard sockets -- bending them could break them, rendering either the front panel or the S-video/composite/optical connectors useless
- Turn the unit so that you can see the EM8621L chip and the 27MHz crystal next to it.
Image 8 (click to enlarge): Shows the location of the 27MHz timing crystal on the motherboard, next to the EM8621L processor.
To the right is another crystal that provides clock for the RTL8100 10/100 Ethernet chip.
Image 10 (click to enlarge): Shows a closeup of the 27MHz crystal on the motherboard.
Note the two surface mount capacitors just to the left of the crystal, marked C40 and C41.
- Connect the video output to something so you can see what's happening
- Connect the power
- Turn the unit on. If you're watching the video on something that uses a different connector to your usual display device, you might have to press the "TV OUT" button on the remote a few times until the image is visible.
- With the unit running, gently touch the 27MHz crystal with your finger while watching the display. If there is any visual interference, or if the unit crashes or resets spontaneously, you have verified the problem. Otherwise, you probably have some other issue and this page isn't useful to you any more. Sorry!
Removing the old crystal
Examine your new replacement crystal closely if it's a surface mount one like the original. Understanding how it attaches to the motherboard will help you to remove the original.
Image 11 (click to enlarge): Shows the underside of the removed 27MHz crystal.
Note how the leads come from near the middle of the package, not from the edges.
Note also the remains of the traces, from their motherboard untimely rip'd.
The original crystal is a surface-mount component, with two leads that originate near the centre of the component and extend, in opposite directions, to protrude just beyond the ends of the non-conductive base. These leads are soldered to traces on the circuit board along their whole length, where you can't see them. Failing to remove all the solder from these traces will probably result in peeling some or all of the traces off the motherboard when you pull the crystal too hard to get it off (I bet you can guess why this paragraph is here).
You want to prevent this happening if at all possible, because it'll give you a heart attack.
If it happened, it's not the end of the world -- these instructions don't have you soldering the new crystal onto the traces anyhow.
What you really don't want is for any peeled traces to remove other components, because that really is the end of the world (at least, for your MG-350HD). So, please, try and get all the solder off.
If you've never done this before, go and get a throwaway surface-mount circuit board to practice on. Any $2 transistor radio will do fine. Practice until you can remove components cleanly.
- Using your desoldering braid, remove all the solder from the crystal so that it lifts cleanly off the motherboard with an absolute minimum of force (ideally, zero force).
- Put the old crystal in the garbage bin. Or something.
Installing the new crystal
If you didn't ruin the traces as described above, you can probably solder the new crystal directly on to the motherboard, using the existing traces.
If your new crystal is a through-hole mount, or if you did ruin the traces (like I did), you'll need to attach the new crystal using the Kynar wire to the two surface mount capacitors labelled C40 and C41, at the ends closest to the EM8621L:
- Cut 2 identical lengths of Kynar wire, and strip about 1mm from each end. This wire is very fine, so be careful. Make them about 10-15mm long, but try to keep the wires as short as possible so that the new crystal is in the same location as the old. You don't want these wires to turn into radio antennas.
- Solder one end of each wire to the leads of the new crystal, so that they emerge parallel to each other from under the sides of the crystal. If the new crystal is a through-hole mount, you might have to bend or trim the leads so that they don't get in the way.
- Bend the wires so that they run right next to each other; you can use a drop of super glue to bond them together if necessary. Try not to bond your fingers to the wires; you don't run at 27MHz.
- Bend the stripped free ends of the wire away from each other, so the end of the pair of wires resembles a 'T'
- Pop a small piece of electrical tape or similar on the motherboard where you'll put the new crystal -- to prevent short circuits.
- Place the wires in between the two surface mount capacitors C40 and C41 -- hold the crystal down to the motherboard with a piece of electrical tape or similar to prevent it wiggling about while you do this. You want the stripped ends of the wires to rest exactly on the solder pads at the ends of C40 and C41
- Put a teeny blob of solder on the tip of your very fine point soldering iron, and touch it to one wire/capacitor junction, just long enough to make a good joint.
- Repeat with the other wire
- Fasten the crystal to the motherboard so it won't wobble about. Super glue or hot melt glue works fine, as does strategic arrangements of electrical tape though the glue is more stable and permanent.
Image 12 (click to enlarge): Shows the newly installed crystal.
Note the dodgy electrical tape under the package, insulating the motherboard and protecting it from scratching.
Note also the teeny piece of electrical tape holding the wires down. A much large piece of tape was applied after this photo was taken.
Observe carefully the shape of the wires attached to C40 and C41. These were bent before the package was put in place.
Testing
Repeat the verification steps (above). There should be no visual interference any more, and the unit shouldn't crash or reset.
Reassembling the unit
Just like they say in all the best car service manuals, installation is the reverse of removal (I always wanted to write that).
Make sure:
- when re-inserting the MiniPCI card, push it all the way in before pushing down. You should have the rounded ends of the spring clips centered in the semicircular cutouts in the sides of the WiFi board.
- When re-attaching the wireless antenna to the case, wind it anti-clockwise about 7 turns before putting it in the hole. Then, screw the nut on the outside in as far as you can before screwing clockwise from the inside. This helps make sure the antenna cable doesn't end up twisted.
Troubleshooting
- Unit won't power on/won't boot
Check the connections you've made with a magnifying glass, or by taking some close-up digital photos and examining them in detail. Make sure you haven't accidentally connected two traces or components together, and that you haven't broken or cut any traces while performing the above steps.
- Unit still has visual glitching/crashes/resets randomly
Make sure that the connections are good -- no dry joints, and that the new crystal isn't somehow contacting another component. If that doesn't solve the problem, then there must be something else wrong that we haven't discovered yet -- sorry.
- My MG-350HD is broken, and it's all your fault! You should never have encouraged me to do this!
Did you not read the many, many warnings above? Did you not read the bit about "no warranty expressed or implied"? I'm sorry your unit is broken, but it really is your own fault.
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