Emax

Hi Jamie,

> electrolitics dont leak any more that was the old types from the 60,70,s the new types dont use oil 

Point taken, but we are talking about old gear.
> 
> the caps fail due to heat which causes oxidiation build up inside the cap which makes it harder to hold charge when it can no longer hold charge 
> 
> they dont fail if not used or over time in storage it the over use and the leaving the psu on constanly not powering down the instruments which is what happens in expensive studio,s where they are left on 24/7
> 
> and the cap does not get chance to cool down 


I have had 2 caps a SMPS in my Morpheus leak all over the board and in 4 in one of my TX816s made in the 80's the other that had been sitting in the cupboard and had barely been used also failed. No thousands of hours and no 'cooking' on these units, but they could have been not so goo from the start, but my experience with Yamaha gear has been very positive.

I was told by a company that specializes in SMPS rebuilds here in Australia that this is common. They very kindly helped me rebuild the power supplies  via email and this was the procedure they used.


> 
> its hard to tell by looking at a cap if its heat damaged the best way is an oscilliscope which can show you the charge and discharge sequence which will show you if the cap is damaged or not

DO NOT DO THIS on a powered up switch mode power supply. 
My understanding is you need an isolating transformer to do this safely.

For a lot of detail of SMPS repair have a look at this link
http://www.repairfaq.org/sam/smpsfaq.htm

Repair techs and they talk about safety a lot here.

> 
> 80 oc cap is only good for 3-4000 hours at 80 oc if you replace for 105 oc grade thay will work for 10-20000 at max 105oc temp 
> 
> so you can see that if an instrument is kept on all the time and reaches a max temp of 80 oc then 4000 hours at this max temp wont last for very long 
> 
> so switch of when not in use they last longer 
> 
> i have an mirage from new and a emax from new that still work from there original psu these machines are over 20+ years old and still going strong but i only switch them on when needed so the caps never get hot enough to oxidise

Different experience, different opinion. Thanks for the info. 

I hate passing on bad info. I hope I haven't done it here.


All the best

Royce

>   ----- Original Message ----- 
>   From: rpcfender 
>   To: emax@yahoogroups.com 
>   Sent: Sunday, November 29, 2009 1:14 PM
>   Subject: [emax] Re: Emax II RIP? (not!)
> 
> 
>     
>   Electrolytic caps have a number of failure modes.
>   They can leak the dielectric and that either appears on the PCB or the top of the cap (which is what yours look like).
>   The cap can swell and distort the case, easy to spot on the top. Even the rubber bung at the bottom can pop out.
> 
>   They can dry out as well which usually you can't spot.
> 
>   They can sometimes develop a short although you would know from the smell and sometimes the bang.
> 
>   And some other not so obvious failure modes as well.
> 
>   Sometimes they exhibit these signs but still work, but it is better to replace them.
> 
>   Electros can fail even if the unit is unplugged in the cupboard unused for a few years.
> 
>   Don't know anything about electronics, can get help? Start by replacing the caps , electrolytic ones first.
> 
>   Word of warning............
>   capacitors store charge.
>   Electrolytic ones (as the are usually a high value) can store a lethal charge.
>   The electro caps in a some types of power supplies are across mains voltage. Here in Australia this is 240v and can kill you even after the power is turned off. You need to wait for it to discharge and check it with a volt meter.
> 
>   Sounds like replacing the whole PS was the right thing to do.
> 
>   Royce
> 
>   --- In emax@yahoogroups.com, "Daniel Baum" <daniel@> wrote:
>   >
>   > 
>   > 
>   > 
>   > >The electro caps looked stuffed, which is typical for the age and they are 
>   > >the first port of call in a rebuild.
>   > 
>   > Excellent. That means that the original diagnosis from chevytravelleruk was 
>   > correct and that changing the power supply was justifed.
>   > 
>   > If I could have rebuilt it myself, then it would have been better to have 
>   > done so. However, since I would have had to pay someone else to do it, it 
>   > was about the same price to get a brand new one.
>   > 
>   > How can you tell that they're stuffed, BTW? It would be useful to know.
>   > 
>   > Thanks,
>   > 
>   > Daniel
>   >
> 
> 
> 
>   
> 
> 
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