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Scott Dorsey Scott Dorsey is offline
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Default overvoltage on audio circuits

gareth magennis wrote:

I have here a batch of SSL channel strips rack mounted.
The regulated PSU that came with them is marked +-18v but actually produces +- 21v with a 1A quick test load, with the adustment pots at minimum as they arrived, .
(I suspect these are 24v based supplies - they are modular linear ones made in USA i think, 2 x "18v" and a 48v phantom)


Who made themm? If they are at 21V with a 1A load, they are likely failed and
might even be running full open.

It seems the channel strips have been running with this supply at 21v for a long time now.

What could be the possible detrimental effects?


Electrolytics will go bad. Can cause failures of semiconductors too, but if
they were going to fail they would have failed by now. If the equipment was
well-designed, they used 25V or 35V electrolytics and the lifetime will be
shortened a little bit. If it was poorly-designed they used 16V electrolytics
and the lifetime will be shortened a whole lot.

I have only had a quick peek inside the first one of eight, and noticed a bulging capacitor on the SSL dynamics card.


They do that naturally, though. They are wear items. It's probably time
to replace them.

I would not power any of them up with this supply at present.


21V isn't enough to worry a lot about but if the regulation in the supply is
not working properly, the noise floor will be impaired too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."