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Jason P
12-02-2009, 21:41
Hi AoS DIYers,

I've a probelm with an old amp I've resurrected from the loft. All working fine, sounding lovely until today - I think one channel has blown in the power amp stage. It's an Ion Obelisk 2. Definitely no signal from the RH channel or via the headphone socket.

On opening the lid, theres a curious smelling liquid coating all of one side of the PCB - its clear but has a distinctive smell (this is the point where someone tells me it's highly poisonous and will, once inhaled, cause death within 24 hours).

One of the large components - possibly a capacitor, it's measured in microfarads on the case and there are 2 (one for each channel) - has seemingly ruptured. If this is the case, a) what caused it - just old age? and b) is it likely to have taken anything with it?

I'll try and post pics later, I'd love to fix it as it's a cracking amp. I may have a go myself if I can find an appropriate guide.

Jason

Puffin
12-02-2009, 21:52
It had probably bulged before giving up the ghost. Is the other one bulging. Take some pics. It may be salvageable. You would have to remove the cap and clean the crap off the board.

Mike
13-02-2009, 18:20
Hi AoS DIYers,

I've a probelm with an old amp I've resurrected from the loft. All working fine, sounding lovely until today - I think one channel has blown in the power amp stage. It's an Ion Obelisk 2. Definitely no signal from the RH channel or via the headphone socket.

On opening the lid, theres a curious smelling liquid coating all of one side of the PCB - its clear but has a distinctive smell (this is the point where someone tells me it's highly poisonous and will, once inhaled, cause death within 24 hours).

One of the large components - possibly a capacitor, it's measured in microfarads on the case and there are 2 (one for each channel) - has seemingly ruptured. If this is the case, a) what caused it - just old age? and b) is it likely to have taken anything with it?

I'll try and post pics later, I'd love to fix it as it's a cracking amp. I may have a go myself if I can find an appropriate guide.

Jason

Then it IS a capacitor. It's not unusual for them to 'dry out' or 'leak' after years of sitting around in a loft, and then go pop after being put back into use. It should be relatively easy to repair, it would be wise to replace the other caps at the same time too. It is of course possible that another component has failed and 'taken out' the capacitor, which might be slightly more tricky to diagnose.

Jason P
13-02-2009, 23:10
Thanks for that Mike, I'll post a pic and maybe get some advice as to what the best replacement would be...


Jason

Jason P
11-03-2009, 22:23
So, I did post pix but after the forum outage my posts went...

Anyway, it was the capacitor that had blown. I've replaced them with some unbranded ones from RS to see if it fixed the problem, and it did - so luckily no other components seem to have gone. However some of the warmth has gone leaving a more brittle sound. I'm guessing it's due to the cheap caps.

So any suggestions please? Originals were 2200uf 35v Rubycons. Suggestions for upgrades on these, and where to buy, would be most welcome!

Thanks in advance,

Jason

anthonyTD
11-03-2009, 22:36
So, I did post pix but after the forum outage my posts went...

Anyway, it was the capacitor that had blown. I've replaced them with some unbranded ones from RS to see if it fixed the problem, and it did - so luckily no other components seem to have gone. However some of the warmth has gone leaving a more brittle sound. I'm guessing it's due to the cheap caps.

So any suggestions please? Originals were 2200uf 35v Rubycons. Suggestions for upgrades on these, and where to buy, would be most welcome!

Thanks in advance,

Jason

hi jason,
try arovox caps, they are one of the best sounding in my view, and wont break the bank. farnell, RS, or CPC usualy have the values needed, you could probably go up to 3300 uf or higher if you want to stiffen up the bass a bit more, it all depends on the type and size of the rectifiers/diodes in the power supply.
hope this helps.
anthony...

Jason P
11-03-2009, 22:50
Thanks Anthony, I think the one's I got were Vishay 136's. I'll have a look out for the ones you mentioned... you say I can go to 3300uf? Any snags I should watch for?

Cheers

Jason

greenhomeelectronics
12-03-2009, 07:42
The previous warmth was probably caused bythe supply collapsing during large transients, it now sounds more like it was designed to sound as the new caps hold the voltage much better. Going larger will usually improve tightness in the bass department.
Dave.