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About av-geek

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  1. Power Base 1 ch1 serious distortion

    Also, check if your capacitors are good. Select AC current on your multimeter, and measure between to + and - rails. You should see DC amounts in the millivolt range. If you see DC in any significant amount, the big electrolytic can is blown and needs replacement, and possibly the bridge rectifier too.
  2. I was using my CT800 at a flea market building with a marginal electrical system. Unbeknowinst to me, the outlets were not grounded. When I placed a mixing board on top of the CT800, the cases grounded together and sparked. After that, I refused to operate my equipment in the building. Only problem was the damage had already been done. The CT800 stopped working in the right hand channel. A short had developed between B+ and ground, leading me to believe it is in Q309,310, or 311. I was looking over the schematic of the amp however, and I cannot seem to figure out for the life of me how the chassis ground works. The speakers are grounded back to chassis ground, and the chassis is at earth ground potiental through the 3rd prong of the power outlet (which was not hooked up in the venue I attempt to use it at!). In a typical power supply, the negative side of the bridge is tied to chassis ground, and the positive side is tied to the components. Of course, in a n AB+B amp such as this, it's different. The negative side is tied to components as well, with the ground appearing to "float" between the B+ and B- supply voltages. Now what has my head scratching is how this actually works. I do not see any ground reference point off the power supply to tie it all together. I would think there would be a center tap on the transformer or something of that nature, but there isn't. From what I can tell, even if I was able to use my CT 800 at this venue without damaging it, I would not get any sound, because the earth ground was missing. Am I correct on this thinking? Also, wouldn't these amplifiers trip GFI outlets when the current from the speakers is detected on the ground terminal?
  3. Which amplifiers in Crown's line have temperature controlled fans? From past experience with the Com-tech line and the CE line, those amplifiers have fans that don't come on until they start to get warm. I thought I remembered at one installation that had macro-techs, that the fans stayed on continuously at a low RPM. I've also noticed many of the competitor's amps have fans that run all the time,which is unacceptable in many of the applications I use them in. Crown amps are awesome guys, keep up the great work!!!
  4. Is your IOC indicator blinking with the beat of the music, if so, I think I know what it may be, and it is only about $35 or so of parts to get it going again. The most common issues with the com-tech series that I've seen is that the big electrolytic cans go bad, and they will even sometimes even take out the bridge rectifier in front of this. This failure can usually be found by checking the voltage going into the finals. These are the screw terminals on the heatsinks. Set your DMM to AC volts. You should not have any more than a few millivolts, if that much of AC voltage going to the finals.