Building Power Supply (AC adaptor stopped working)

[nelly]

Hi there,

After completing my previous xoxbox (thanks for all the help on here, especially to guest of course) I decided I'd like to build another one for a friend.

Wouldn't you know it I've ran into a problem straight off the bat.

I've gone through the first section and having placed all the components I've had a strange problem where by my power supply has stopped working. (The actual AC adaptor)

I measured the Voltage at the input and was getting nothing.
Measured across C3 (VAC I think) and got 30VAC. Thought that was odd measured across C5 and got nothing. Changed multimeter to DC and measured again and got nothing on both caps.

I very briefly got 5.2v off pin 5 on the IC. But that started slowly climbing down and down.

Oddly however I was curious as to why there was no power so tried measuring the voltage of the AC adaptor itself and got nothing. Thinking something was wrong I measured the AC adaptor of my other xox AC adaptor and that was working fine so I plugged that in to see if I got any measurements but still couldn't get anything.

I then unplugged the second AC adaptor and lo and behold that AC adaptor was also 'broken' now.

Is there any way that the AC adaptors could break plugging them into the I/O board? I've literally only put in the first sections components and am flabbergasted as to how the AC adaptors could have broken?

I've double checked all components to make sure all the capacitors and diodes have been put in the correct way etc..

It's just so strange how both AC adaptors now don't work, leaving me in the dark to test further...

[guest]

there might be a short on the input stage
so an internal fuse on the adapter is getting blown

measure the resistance at the input jack
and check with the meter leads reversed as well

are both adapters giving no ac or dc readings
when they are not plugged in

[nelly]

Hello again,

Thanks for the quick reply.

I've used my multimeter to test the AC adaptors to see if there was any AC or DC coming from them while they were unplugged but got nothing.

I'm not getting any resistance on the input jack. With leads reversed as well. Tempted to take my pcb out of my own xox and see what readings I get across the input jack. But I'm worried about breaking that as I need it for my end of year project.

I have inquired how much it would cost to replace the pcb and the small amount of parts used as I'm not sure how I'll be able to test this problem without blowing the new adaptors I've bought (25 euro for the two of them) So I'm not tempted to make a 12 euro mistake every time I plug the things in.. :/

[aminoacid]

if you try with your finished xox again with both adaptors, do they even then seem to not be working?

whats the mA rating on them?

[nelly]

if you try with your finished xox again with both adaptors, do they even then seem to not be working?

whats the mA rating on them?

Both adaptors have stopped working completely. Tried hooking them up to my xoxbox but nothing happens.

They're 'official' adaptors included in the kit.

mA rating on them is 500mA..

[aminoacid]

adaptors at strike!


see if theres any shorts further in the power section. start by checking all ic´s for ex. with out any adapter plugged in of course.

[guest]

when you say no resistance at the input jack
im assuming you mean that it is an open circuit

also
did you measure the resistance from inside the jack
where the jack actually touches
or from the pcb solder points
it could be the short is actually in the jack someplace
you could cut off the plug end from the adapter
and strip the leads and use that to measure

you can probably saw the adapter open
and short out the fuse thats in it
but id check for shorts further up the line first

[nelly]

Sorry yep, I'm just getting a 1 from the multimeter. It's not the best multimeter in the world but does the trick.

I measured the resistance from inside the jack as well yep.

By jack do you mean the female input? Or the male part?

I'm assuming female part (soldered to pcb) as both AC adaptors have been fried.
I might cut off the end of the adaptor. But I've already gone ahead and split the AC adaptor open with a screw driver. Didn't find anything but a transformer. Was very odd actually.

Split it open and there was a transformer with two wires that were soldered directly to the pins of the european plug.

For some reason I have a sneaky suspicion that this all has to do with the female 2.1mm adaptor on the board. Annoyingly (really pissed off with myself actually) I looked at the parts list and started soldering them in one by one, having finished the other xox I was used to finishing each 'section' and then testing.

Forgot that for the pcb you test each little component as you place it.

Maybe a continuity test of the plugs to see if they're connected might work?

[guest]

the fuse is usually wound on the first wrap of the transformer
so if you peel back the tape around the transformer
you will probably see it

also check that the outlet youre plugging into is good
it might have tripped the fuse up the line

measure the resistance of the wall adapter itself
both between the mains plugs
and between the 9v outlet plug connections
they should both be pretty low ohms

[nelly]

Ah I see, excellent, I saw something wrapped up but wasn't sure what. I'll have a gander tomorrow at some stage. Creeping up to 1am so need to get to bed but will double check all of the above tomorrow again.

As always your help and time is much appreciated. Thank you guest. I'll report back with any findings I might have.

Steve

[nelly]

adaptors at strike!


see if theres any shorts further in the power section. start by checking all ic´s for ex. with out any adapter plugged in of course.

Apologies Aminoacid, I didn't even spot your post there last night. Thanks for the heads up. Going to try and check the rest of the circuit. Not 100% sure where I should be looking for a short etc. But will use the voltage schematics to see where grounds should be and then work from there.

Thanks again for the heads up!

[aminoacid]

no need to be sorry

dont forget to investigate the power jack further as guest says!