Dear Sir, I recently did some repair work on an Orion 225 HCCA amplifier. Replaced some shorted output transistors and one audio Op-amp, however now I'm getting distortion coming from the right channel. Could another audio Op-amp be at fault, and if so, which one ? I replaced the first audio Op-amp chip in the center of the circuit board right below the two muting transistors. Any help would be greatly appreciated !!
You say the outputs were replaced? Did you check the drivers?
You may have the same thing I had in this thread here: http://www.diyaudio.com/forums/car-audio/177733-orion-2250-gen-ii-output-help.html
You may have the same thing I had in this thread here: http://www.diyaudio.com/forums/car-audio/177733-orion-2250-gen-ii-output-help.html
Mr. Perry Babin, help please !! Re; Orion 225 HCCA Trouble
No, unfortunately, I don't have oscilloscope, and yes, it is the yellow wire that corresponds to the right channel. I've made a visual check of some resistors, and there is indeed a few that show discoloration. What color are the 75 Ohm transistors in question ? For thoroughness sake, where on the circuit board and what identifying numbers do the driver transistors have. I believe the amp might indeed be drawing excessive current as the toroidal transformer heats up, even when there load is applied to the amp.
No, unfortunately, I don't have oscilloscope, and yes, it is the yellow wire that corresponds to the right channel. I've made a visual check of some resistors, and there is indeed a few that show discoloration. What color are the 75 Ohm transistors in question ? For thoroughness sake, where on the circuit board and what identifying numbers do the driver transistors have. I believe the amp might indeed be drawing excessive current as the toroidal transformer heats up, even when there load is applied to the amp.
O.K., now the amp will not power up. It only turns on for a few seconds or a minute at the most. I checked pin No. 12 on TL747, it shows 13.9 V when the remote signal is applied. Also checked pin No. 9 and 10. They both show 5.4 V. There is no power, positive or negative, on the large emitter resistors. What could the problem be now ??
O.k., at one end of the large power resistor I get 15.32 V, on the other end 1.27 V. The Diode has 1.27 V on the anode side, .41 V on the cathode. On the transistor I get 0.00 V on the square pad, .41 V on the middle pad, 0.00 V on the outer pad. Incidentally, the large power resistor get hot to the touch, is this normal for this amp ??
O.K., I took one last measurement of voltages before pulling the transistor, for some reason it then showed 2.30 V at the one end of the power resistor, 15.37 V on the other. The diode showed 2.3 V on the anode side, 1.5 on the cathode side. The middle pin on the transistor also showed 1.5 V. I then pulled the transistor, nothing happened, all readings remained the same. Also, the power resistor remains hot to the touch. What could be wrong ?
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