HIFONICS ZXi 1008 car amp stuck in protect mode

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#122
No, what i mean to say is that is when the center leg of of the rectifier is hook up that is when the amp goes into protect after about 10-15 sec after power up. Could that mean that one of the power supply caps is bad and if so how do I check for that?
 
#123
Found a DC offset at one set of the speaker terminals. Starts off at about 1vdc and goes up to about 3vdc before the protect circuit engages how do I troubleshoot where the offset is coming from? If I have no output transistors in the circuit there should be no voltage getting to the speaker terminals correct? I will be waiting for a reply on this?

Thanks
Tom
 
#124
got one of the channels rebuilt but I have real bad distorted output and it is really low in volume. I do have good outputs from the NJM4558 Dual Operational Amplifiers, but I do not know how to check for output from the current and voltage gain stage. Do I take the output off the collector or emitter of this stage? Please help.

Thanks
Tom
 
#129
You're not going to find an identical diagram. In the repair business, many times, all you get is something close. Take an hour or so and see if you can find the similarities. This repair has dragged on for a long time. If you can list the corresponding components between your amp and the diagram, it may be possible to find the fault quickly.

Don't expect any of the numbers to match. You're looking for connections between similar components.
 
#130
OK, I read one of you other responses about checking op amps outputs on both channels so I am going to do that and look at the diagrams and see what I can figure out. I replaced all of the small signal KTA1266 and C3198 transistors on the left channel with A1015, C1815 transistors respectively. I did notice that from testing the base - emitter junctions that I was not getting any voltage drop across some of them, but I check the diodes with diode check on my meter and they seem to be OK. I do have to replace some of the FET's on one side of the power supply because they tested bad however the other side is working and these two supplies are in parallel with each other so there is rail voltage and the output transistor do have audio on them but it is low, distorted and very staticy.
 
#132
Found the problem with the output on channel 1 :whacko: -- Bad crossover switch, I moved the switch around and started getting audio out of the speaker output after testing all of the op amps.

I will update you when I get the rest fix.

Thank you for the help and the information.

Tom S.
Wells, MN
 
#134
I have very high current going through channel 2 on the amp now. It causes the resistors that connect between the collector of one driver to the base of the other driver to get hot and burn out please see attachments.

Thanks
Tom
 

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#137
I'd use the MJE15030 and MJE15031. You'll have to add an insulator behind them if the other drivers were on the heatsink without an insulator. Someone else may have suggestion that are closer to the original but the ones above have proven to be good subs for drivers when TO-220 drivers were needed.
 
#139
Just to let everyone know that is following this thread that the repairs on this amp are now complete and that amp is back together and working. Turns out the only real problem with it was a broken crossover selector switch. Replaced that switch over the weekend and the amp is working great. Lots of power. Thanks to all of those that helped me on this, especially Perry who took the time to explain some of the concepts of electronics that were new to me.

Thanks again
Tom Steinhauer
Wells, MN
Thomas Steinhauer Computer Repair
look me up and like on Facebook http://https://www.facebook.com/ThomasSteinhauerComputerRepair
 
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