Inverted polarity on Sony CD200

[Changes]

I have a Sony MVC-CD200 digicam. It uses expensive LiIon batteries and a weird proprietary socket for the DC power supply. I wanted to make an external battery pack, so I cut off the cord from the DC power supply and connected it to a holder with 7 AA cells. I left screw-on contacts on the power supply so I could switch the cable around as needed. This worked perfectly.

Anyway, yesterday I went to connect the external battery pack and got the polarity wrong. When I saw that it wasn't working I just took the plug out, inverted the contacts and plugged it back in, expecting no trouble; this has happened to me in the past with other appliances and they never suffered any permanent consequences.

Instead, the digicam didn't turn on and now appears very dead. It doesn't work from any power source; no lights, no LEDs, no glimmer of life at all.

I'm about to open it, but I've no idea what to look for. I have very limited knowledge of discrete electronic components, so I can probably figure out what to look for if someone instructs me, but without help I'm lost.

Note that there's no burnt ciruit smell, so I'm hoping no expensive, hard to replace ICs got fried. Ideally, I'd love it if it was just some easily replaceable diode or something.

Please help me, I really like this digicam... it's old (bought old stock for ˆ50), but takes better pictures than many modern models that cost 5 times as much.

[vtech]

....Keep in mind these units are very sensitive & easily damaged. Really should not override the original. Iith ion batts utilize a sense line that communicate with processor as far as charge condition --hence the special connector

....So you've either lucked out & blown one or more of the 6 picofuses that are inside the unit OR managed to blow out the DC-DC converetr IC which is not available seperatley. & lets hope non of the eprom settings are corrupted. Here's a glance shot of the circuit.. Good luck

[Changes]

Thanks. I've opened the CD200, but it's going to take some careful disassembly to get to the power supply board. There are stacked circuits all over the place.
How do I test the fuses? Is it just like a normal fuse (so I have to use the resistance function of the multimeter) or is it something fancier?

[vtech]

..Yes indeed it is stacked & rather difficult. Have to be xtra careful on ribbons & connectors--there are no reversal once broken/torn

As far as fuse, it's just like any other fuse only much much smaller & it is soldered in place . You must have the proper soldering equipment/skills. If not, do not attempt it.

[Changes]

After a long delay today I finally got to it, and after a LOT of cursing managed to dismantle the thing.
I took a picture of the power board:



The only things I think can be six picofuses are those small components I've drawn a red rectangle around. Am I right? Are they indeed the offending parts?

If I'm right and they are, is it conceivable that I've blown F1 through F5? I tested them with the multimeter, and the only one that tests closed is the topmost one, F6... the others all test open.

Also: since I a) lack the soldering ability and b) have no idea where I could get the replacements, would it be really bad if I just bridged the contacts with a tiny blob of solder? No fuses blew until I applied reverse polarity, after all, so it stands to reason that they aren't really needed, provided I take extreme care about how I feed the CD200 in the future.

[vtech]

I'd have to say it is somewhat unusual to pop 5 of them, but it is possible.(just make sure that your probe leads are making good contact)

--while it is hard to tell for sure, but it may NOT be a good sign(major failure?). It is never a good idea to jumper fuse protection where you have no way of at least monitoring the current draw. If you override the fuse, remember you are defeating it's purpose & won't get a second chance & if infact there is still a short, it is pretty much a guaranteed failure down the line or ---you MAY get lucky w/out any more circuit protection.
(I'd never try this on higher voltage applications)
...Another way to get an idea is to try to measure the resistance from circuit-side of the fuse & if you register low ohmage, more than likely indicates a bad/damaged device down the line.

[Changes]

Do you know what's the rating of those fuses? I may have found a source either of them or of others I can solder on with a bit of wire... hopefully I can do it without splotching solder all over the place.

How exactly do I measure the resistance circuit-side? Where do I put the probes? How low is low ohmage?

Thanks for your patience

[Changes]

*bump*

[vtech]

They are all the same microfuse rated at (1.4Amp@ 36V).

Original Sony's number 1-576-406-21 which has been subbed to 1-576-406-11. (ok to disregard the 36volt rating as it pertains to physical size if looking for a generic microfuse)

...No set value as low ohms (suspect 15 ohm's or below--providing not reading some sort of cap charge/discharge)

...By circuit side meaning to measure from regular ground to any/all the lines to the right of the fuse bank feeding IC001..etc. (schematic posted earlier)

[Changes]

In the end I gave in and soldered the contacts together. Took me two hours to put the thing back together, and it's still not working. I must have fried the IC when I applied inverted polarity.

Thanks a lot for your help, I wouldn't have known where to even start without you. Sadly, no good results...
If you have some other idea about anything I could do to repair it I'd be happy to know it... otherwise I'm through with this thing.

Typical of sony: make a beautiful piece of gear and then apply abundant stupidity and proprietary everything. Would it have killed them to add a simple reverse voltage protection, as everybody else does? Maybe even use a *gasp* standard, universally compatible barrel plug?

I'm not trying to blame them for my mistake; I should have been more careful with the external pack. But had I done it with any other digicam, nothing would have happened.

Gah, I hate Sony.[/img]