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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Mixer problem
"Anders N. Vinje" wrote in message ... 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 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 |
#2
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Mixer problem
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. |
#3
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Mixer problem
replace the caps.
and also check for bad bridge rectifiers ! they some times cause periodic shorts. Anders N. Vinje wrote: 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. |
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