Anders N. Vinje said:
Hey.
I have this old Samic SM-810 Mixer that generates alot of hum. And somtimes
there is a short burst of current that passes trough making a loud pop!.
This is really annoying when making music.
I have replaced the Opams that where inside with Burr Brown OPA1342. It
helped alot against the humming and noise it was generating. The old Opams
where ST TL072CN type. One Channel even had a Philips NE5532. Well i bought
i used. So i guess the guy who had it before made som changes. well anyway
this part goes into my old parts container. But here is still alot of hum.
But i am wondering what generates that pop somtimes. Bad capacitator
somewhere, maybe? I was thinking of replacing the the electrolytic mains
filtring capacitators. With som lager ones. Something like 10000uf. There
are there are two SMC 25V 2200uf on the + to gnd And two at the - to gnd. I
only have a multimeter or else i would have seen how much ripple its
generating in none use mode. The OPA 1342 uses a couple of mA more then the
TL072. But i have heard the NE5532 is a sucker on quicent current. Maybe it
sucking to much current allready?. I dont know. I have been looking for the
schematic for this mixer, but i seems that Samick dosent exits anymore.
Anyone know where to get it?
Any suggestions on this mixer especially the poping would have been much
helpfull.
Anders.
PS. After i have been posting on this newsgroup. I get those irretaing MS
advise or something mail with a virus. I should never have used my own mail
address.
I can't help you much on your specific problem, but one thing I will say, is
that when modifying a piece of equipment, it's always best to have it
operating to it's original spec before trying to improve it.
As to the problem: capacitors are definitely suspect, especially the p.s.
electro's. There's very little to be gained by increasing the value--at
least as much as you suggest--on a small-signal device such as this...better
to add an improved supply outboard of the unit. (Again, fix--or at least,
definitively locate--the original problem before making mod's.) Another
very real possibility is that you have a grounding problem somewhere in the
unit. Mixers are pretty complex units with lots of audio paths. If it has
plug-in channel modules, remove them all except one, and see if the symptoms
improve. Remove, clean and reseat all plugs. Clean all controls and
switches with a good quality contact cleaner. Tighten all jacks on the back
panel...sometimes they loosen up over time. Check solder
joints...especially where cables ground to the chassis. Look for corrosion.
Good luck, but remember: fix it *before* you modify it!
jak
