friend needs help

[goodsguys]

Hi. And thanks for taking the time to read this post.

A few weeks ago i upgraded the power supply smoothing capacitors to panasonic fm's in my firestone fubar dac and noticed an improvement in sound quality. I then upgraded the rest of the capacitors on the board keeping the same capacitance and voltage values, checking the soldering job as well.

And the darn thing never worked again.

Later, I upgraded the capacitors in my zero dac and that stopped working as well.

Has anyone else had similar problems to this. Is this capacitor upgrading not as simple as it looks. Does the different specifications (impedance, ripple current values etc) of replacement capacitors change the current or something in the circuit creating a dangerous situation.

Could really use some help here guys, £400 worth of dacs just bit the dust.

Many thanks in advance. John.

[The Grand Wazoo]

Hi Mark,
Much as we all feel for your friend & his plight - and there are folks here who would be glad to help and are well equipped to do so, I'm sure - there is a little Art of Sound housekeeping you need to attend to first, please.
Would you mind going over to the Welcome section to introduce yourself to the community as was requested in the email you received when you joined. Just go here (http://theartofsound.net/forum/forumdisplay.php?f=15) & start a new thread to tell us a little about yourself, you system (& your friends if you like!) and your favourite music.
Thanks a lot in advance.
Cheers

[sq225917]

It might be that you missed replacing some bipolar capacitors and replaced with polar caps instead. Or you could have fried one on fitting with too much heat. Or maybe you lifted a pcb track on removing the old ones. or maybe you just got one in backwards! Some caps, particularly styrene ones are very sensitive to overheat.

A picture tells a thousand words. You did take 'before' shots as reference didn't you?

[goodsguys]

Hi. Many thanks for the replies.

It is genuinely appreciated.

Some of the caps i replaced were 2200uf with a tolerance of 20 percent. The new onces could have been 1760uf due to this tolerance, would this have caused any problems on the board perhaps with current levels suddenly being low.
Also do you think it is wise to let new components burn in for a week or two before cranking up the volume or subjecting them to any kind of pressure as their behaviour is supposed to change after time.

Many thanks in advance. John.

[YNWaN]

It depends on the circuit design whether a variation of 20% would be important - what is the tolerance of the capacitors that were removed?


Also do you think it is wise to let new components burn in for a week or two before cranking up the volume or subjecting them to any kind of pressure

No, it will make no difference = if they don't work now they definitely will not start working in a few days.
_______________

Dry or poor solder joints is a likely reason, You may also have accidentally bridged a circuit track whilst soldering. You could have killed one of the capacitors with excess heat or you could have accidentally burned one of the other components with the side of the soldering iron whist concentrating elsewhere. As suggested earlier, you could have soldered one, or more, in with the wrong polarity. To be honest, you could have done loads of things - a couple of decent pics of both sides of the board would be required to make any more definite suggestions.

[sq225917]

As long as new and old caps were the same value and tolerance it's unlikely that any actual difference would matter. You are unlikely to find any company that 'selects' the best value electrolytic caps from a box load- there's no point as there's no way of knowing how they will measure once once run in.

Run in will not 'fix' this amp. You have made a mistake somewhere or damaged something.

[StanleyB]

Smoothing caps are the most forgiving kind. You can use a different brand with a different tolerance and even different capacitance 9within reason) and get away with it.
But others caps in a design can be far more critical. Caps exist in a wide range of material construction, and for good technical reasons. Capacitance value and voltage alone doesn't guarantee that swapping one brand for another is going to improve anything, or even get the equipment to work.

[Puffin]

There used to be a guy a couple o' thousand years ago who was Simon, also called Peter. You are Mark, also called John....Coool:lol:

[goodsguys]

Hi. Many thanks for the replies.

I'm afraid i didn't take before photos as i thought : I'm just replacing a few capacitors, what could possibly go wrong?

At the moment when i turn the dac on it gives off a burning smell from a LM1117T 5.0 regulator, apart from that the thing is totally dead, no lights or sounds.

What do i need to measure the values of the components on the board, i've tried a multimeter but the other components are interfering with the component i am tring to measure and i am getting a wrong reading from the resistor and capacitance values printed on the side of the component.

Many thanks in advance. John.

[pete_mac]

Check and double-check the polarity of each and every capacitor that you replaced, and also check your soldering to ensure you haven't accidentially shorted the capacitor leads or created solder bridges between adjacent traces on the boards. Something is certainly awry. :(

[StanleyB]

It does look like a short. If it was a wrongly inserted cap you should have heard an exploding cap by now.

[YNWaN]

Yeah, I can't really see how the symptoms described could be down to anything other than a short. Have you accidentally shorted between tracks with your soldering, or dripped solder onto the board? If you are feeling brave, take a picture of the solder side of the circuit board and post it - so that we can assess the quality of your soldering (perhaps it is excellent - but I have seen lots of 'piss-poor' soldering over the years).