Hi Everyone,
Hope you're all well - it's been a while!
I just wanted to pop something up to thank JohnSWimer and VirusKiller for help with fixing my G98. Mine wasn't obviously the power supply, but after checking John's thread and a bit of good advice from VK, I checked it properly and it was. I wanted to put this in to help future owners. You might not want to press on unless your G98 has been misbehaving (mine got warmer and locked up more frequently over time as the PSU failed to hold on to the rope and keep away from the light)...
It was the
G98 Locked up on Boot thread that helped me out.
Failure ModeA good PSU can output up to 6A on the 5V rail. There's a peak in power requirement at boot up. If your power supply can't pump out 2A, then the spindle will fail to spin, your G98 will appear dead, but if you place an ear next to the drive you'll hear it whirr once every 2 seconds or so as it goes through a boot up / reset cycle. It will happily do this for hours. Your wife will also assume that you've gone mad and are cuddling your dying DVD player. I would understand that - I was very upset about mine. We're all friends here. If your power supply is a little more capable (2A to 3A), it might get past that, but then get stuck at the Meridian logo (that's what John was seeing). It takes just over 4A to boot up reliably (according to my bench supply, set to current limit at 6A).
Why it's not obviousI should have known better. The boot loop does suggest a power problem, but when I checked the rails with my Fluke, they looked solid - I saw no more than a 0.1V drop as it ran. The power supply had failed so elegantly that it brought the supply down and back up again so quickly as to be barely noticeable. If I'd bothered to plug a scope in, I would have seen a dip. It was VK that suggested I take another look, and after running the 5V from a bench supply, it became clear that the PSU was at fault.
How to fix it:
Buy a new PSU. There's a minor typo on John's thread. This is the PSU you're looking for:
Manufacturer: EOS
Model: VLT40-3200
Spec: 40W, 5V@6A, 12V@2A, -12V@0.5AIf you're in the UK, you can get one from
RS part num 377-6845 for �33 ex VAT.
Funnily enough, the MTBF is rated at 100,000 hours which is 11.5 years for something that's left on the whole time. It had a full life. I didn't feel the need to look into other power supplies because this one failed in such a benevolent way (maybe I was lucky). It is listed as having over voltage protection.
To fit it, you'll need to:
Prepare - personally I like to leave it plugged in to ground it,
but have it switched off both at the wall and the back panel. If you've got one, wear an anti-static wrist band, if you don't, remove your slippers / shoes (seriously), and touch the outside of the BNC connectors on the back once in a while. If this makes you feel nervous, you might want to get a knowledgeable friend to help. Don't what ever you do make a home made ground strap by attaching your watch to a radiator. Real anti static straps have a 1M resistor in them to prevent you being the fuse that shorts the live wire. You'll probably survive an accidental live touch, but not if you've earthed your other hand. Don't worry too much, though - the mains has been pretty safely looked after in the G98. If you're sensible you'll be fine. If you leave it plugged in and switched on as you remove the PSU, then clearly you're a two bar heater for a few seconds and then plant food.
I also like to take photos to help reassembly later in case I miss something. Pay particular attention to cable connectors and routing.
I've detailed the steps in painful detail. Don't worry that it looks long, I've just mentioned every bolt. You'll need to solder at one point, but as long as you've got a good iron, you'll be fine. Maybe practice on the old one? If building a PC or changing a hard drive is three Haynes spanners, this is about four. You're not going to solder anything smaller than a screwdriver tip.
1) Remove those four lovely shiny hex bolts in the corners of the top panel. Lift the outer top panel off.
2) Remove the half million horrible CSK screws holding the top plate one. Wince at all the little bits of swarf that come off (and make damn sure they get nowhere near the insides!). Carefully put the top plate (with glued on glass) somewhere safe.
Now pause and marvel at the wonderful insides. Look at that massive grounding cage around the drive. Look how they've put the PSU as far away from the audio board as they could (next to the display board). Look at those caps where the power gets redistributed (actually seriously, look at them - if the tops are bulging (mine were), then you'll want to replace them). 1000uf, 16v (I went for 25v). As far as I could tell, one isn't connected. Pay particular attention if one looks flat and the other three look bulgy (mine did). Nice of M to supply a control capacitor for visual inspection!
3) Double check that all is turned off (maybe unplug the mains cable as well here) and remove the two pin connector at the front of the PSU. Also remove the 6 pin connector at the rear. There are latches which key the connector, but you might want to sketch the connectors and the colours on them. Draw a smiley too, it will calm your nerves.
4) Remove the nut holding the ground strap to the chassis. Notice that there are two anti shake washers - one above and one below the ring to help contact.
5) Remove the four nuts plus washers holding the PSU case in place. If you've recently unpowered your G98, treat it with respect and don't touch the pcb - those capacitors are big and could have kept some charge. It won't kill you, but you'll feel some sympathy for those chavs being tasered on TV.
6) You'll notice that there are four torx screws holding the PSU to the case. I love torx. All screws should be torx. Remove them and remove the PCB. Note which hole the ground strap was threaded to, and how it was routed around the posts.
7) Pull the heat shrink back up the ground lead to expose where it's been soldered to the spade connector. I was tempted to stick a spade connector on the replacement, but decided to stick with soldering because it's lower resistance and that's probably why Meridian did that.
8) Unsolder it. Probably should have mentioned that before the last bit.
9) I tested the replacement PSU before plugging it in to my precious G98. It's not really necessary, but probably good practice. Strictly speaking it requires a load to be accurate (at least 0.5A on the 5V), but it should read within half a volt or so even open circuit. If it doesn't, it doesn't mean it's broken, but you might want to get hold of a 10ohm >2.5W resistor (remember ohm's law?) and put it across the 5V and try again.
10) If you're happy with the PSU, solder the ground lead on. Remember to tin the spade first. Push the heat sink down - it'll probably fit.
11) Remember that one screw that had a washer? It was next to the grounding spade. Notice on your old PSU that the copper is exposed next to that screw hole. That's another grounding route. If your new PSU has solder resist over the same area (mine did), scrape it back with a scalpel to allow the screw to connect. You might want to check that it's connected to the ground lug, but I'd be amazed if it wasn't. Only a madman would have something other than GND next to a screw hole.
Like the best Haynes manuals, reassembly is the reverse of removal. Take comfort in the fact that you'll do both again as the universe contracts if we avoid a heat death.
Finally - if you get stuck - message me. Or post something up here. This forum is full of really great techy people who will help you out.
I hear the more analogue forums are just full of really tetchy people
Good luck!
Mark.
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