I am after a resistor For my A1200 mobo..?

[spannernick]

On the back of the A1200 mobo the are small capacitor and resistor,its a orange capacitor not resistor.

Its a A1200 Rev 2B, next to the capacitor is a number C30C any ideas..?

I think it has something to do with the hard drive cos its not working.(Not booting on startup)

EDIT:Its a capacitor not resistor,Me mad..

Can a admin change the tittle for me please,thanks...???

[Steve T]

what leads you to think a resistor is preventing the HDD from working?

[spannernick]

Well the resistor is black and smells like it's blown.You know that smell.Like something has melted.

And the HD CF works in my other A1200 and this board it's not booting from it,Only coming up with the disk screen.

If it helps the resistor is under a small chip thats on top by the RGB connector.

Here are 2 pictures ,can you spot it..??

[Zetr0]

@spanners

C30C would suggest a Capacitor - so lets have a lookie at the A1200 schematics

Sadly I cannot find C30C linked to the IDE in anyway - what I have found is R971 which is a 4.7k pull-up to VCC (+5v).

Take some pictures of your board, I may be able to offer better advice =)

[spannernick]

Just did post pictures,look at the post before yours.Sorry yes its a capacitor not resistor,if you look below it there is 3 resistors called R217.

Here is a close up,there she is...

Originally Posted by Zetr0

@spanners

C30C would suggest a Capacitor - so lets have a lookie at the A1200 schematics

Sadly I cannot find C30C linked to the IDE in anyway - what I have found is R971 which is a 4.7k pull-up to VCC (+5v).

Take some pictures of your board, I may be able to offer better advice =)

[Zetr0]

C30A - to - C30C are .47uf Monolithic 2012/805 SMD based capcitors.

just check with this gauge -



These are used as part of the Video Decoupling Circuit- I suspect at some time there was a pull of current a tad higher than the capacitor could take - possibly a GenLock device?

Sadly this has nothing to do with the IDE - I suspect you have may have a leak in part of the capacitors and possible short traces on the board (in and around the IDE header) if it isn't presenting anything on the IDE Bus.

[spannernick]

I tested it with a multimetter on the 200 setting and it says 81.0 then I tested the one next to it and it says the same so it looks like its still working,well I wouldn't have a display of the disk animation on the screen would I..??

So I need one of these then,.47uf Monolithic 2012/805 SMD based capacitor,where can I get one from,best place and cheap..?

Thanks Zetro for the help..

[spannernick]

Can a admin change the tittle of this thread for me please,thanks...???

[Zetr0]

No worries Spanners - its good to see you on the boards!

I am wondering if this problem is related to this one

[spannernick]

Originally Posted by Zetr0

No worries Spanners - its good to see you on the boards!

I am wondering if this problem is related to this one

No thats a another A1200 I have that I use thats a 1D3,this board has been in my wardrobe where I keep my computers,there is not closes in there...I didn't check the board before plugin it in and there was a little wire on it,it was between the modulator and the IDE connector,don't know how it got on there cos the board was standing upright.It was so small you couldn't see it but came off when I turned the board upside down. Its amazing this is working cos the last time I tried it,it was blank,and yesterday came back to life,but yep the board needs some TLC.I always like having two of everything just incase.

[Steve T]

Originally Posted by spannernick

You know that smell.Like something has melted.

Yes, I'm familiar with it....

OK didn't realise we were talking about different boards! I guess if the short is cleared you might get a fully OK 1200 back by replacing the obviously blown component... its somewhere to begin anyway but i'd suspect further issues beyond that which might be harder to fix.

[spannernick]

Originally Posted by Steve T

Yes, I'm familiar with it....

OK didn't realise we were talking about different boards! I guess if the short is cleared you might get a fully OK 1200 back by replacing the obviously blown component... its somewhere to begin anyway but i'd suspect further issues beyond that which might be harder to fix.

OK thanks,Is there a good place where I can get this capacitor from,maybe Maplin or a site online..?

Can I replace it with a normal capacitor,for the time being,until I buy one,I have a 47uf capacitor in my toolbox..?

[Steve T]

Originally Posted by spannernick

I didn't check the board before plugin it in and there was a little wire on it,it was between the modulator and the IDE connector,don't know how it got on there cos the board was standing upright.It was so small you couldn't see it

the modulator can is same as ground, do you know which pin was shorted to it? I think the pins closest to it on the IDE are 3.3v, so thats probably not good, end up with a lot of current going through parts of the board which can't deal with it, well you see the results...

not meaning to kick you when you're down but this is a lot like the same mistake made with the other board - insufficient inspection before powering on... Or rotten luck or a bit of both.

[Steve T]

Originally Posted by spannernick

OK thanks,Is there a good place where I can get this capacitor from,maybe Maplin or a site online..?

Can I replace it with a normal capacitor,for the time being,until I buy one,I have a 47uf capacitor in my toolbox..?

like a small disk ceramic? I might try that for testing if its the right value and is still good after rolling around in your toolbox i mean its possible... but the SMD pads aren't really designed to take the strain of a bigger thru-hole component (which are meant to be supported physically by being inserted in the board itself).

*edit* you know, i think in the interests of doing things right and patience, just order a replacement cap of the correct spec, you may cause more issues trying to bodge a different package onto the board. just my 2p, if you go ahead be super-careful to not rip up any tracks, like i said the big component is not properly supported by SMD pads.

[Daedalus]

Originally Posted by spannernick

OK thanks,Is there a good place where I can get this capacitor from,maybe Maplin or a site online..?

Can I replace it with a normal capacitor,for the time being,until I buy one,I have a 47uf capacitor in my toolbox..?

You won't get SMT capacitors like that from Maplin. Bear in mind it's a 0.47uF (i.e. 470nF) capacitor, not 47uF, so a "normal" one probably won't do the job. To be honest it should work fine without that capacitor. It's just for decoupling the video power rails and there are other capacitors nearby that can take up the slack until you get a proper replacement. Your best bet for capacitors like that would be industrial suppliers like RS Components or Farnell.

As for the IDE short, that's nasty If you're lucky it'll simply be a burned trace somewhere near the IDE port (the traces are quite fine there), particularly the +5V supply on pins 41/42, which would be easy to check with your meter. But if you've damaged some of the logic it might be bad news since it's not protected - those data and address lines connect directly to the CPU and custom chips...

[Steve T]

semi-related question, is the 1200 a 4 layer board? Also would using a current limiting PSU for testing the board have prevented this occurring? thanks!

[spannernick]

Ok will not do that then,I will buy the proper capacitor for it then,It can wait,its my backup board anyway.Time for some googling I think..

Thanks for all the help.

[Zetr0]

@Steve T
All IDE IO (header is 5v) thats 5volt TTL signal and there is a +5 volt power - there is no 3.3v power on the A1200 motherboard.


@Thread
I suspect what has likely happened is a short on the signal layer between signals not power / ground or there would be a burning mark on the PCB in or around this area.

I would replace C235, C236 and C239. I would also replace C21, C409, C459 and C460 should that it be installed.

From that ensure the area is clean and no shorts exist between the pads and layers by using a multimeter in "continuity mode" before installing new capacitors.

[Zetr0]

@Spanners

if you want a cheap set of mono-ceramic caps - here is a good one from eBay


10x 470nF 0.47uF 0.47µF 10% 16V 0805 SMD Ceramic Capacitors
I am not affiliated with this sale


While 16v is best, you can go up to about 25 volt 0.47uF (470nF) - I hope that helps

[Steve T]

Originally Posted by Zetr0

@Steve T
All IDE IO (header is 5v) thats 5volt TTL signal and there is a +5 volt power - there is no 3.3v power on the A1200 motherboard.

whoops, sorry, don't know why I wrote 3.3!...thanks