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twistedQ 8th July 2012 07:33 PM

Kicker KX1200.1 Problems
I am currently working on two kx1200.1 amplifiers, both 04 red boards. The problem I am having right now with one of them is that the rail voltages start low around 10V and then climbs upward towards 50v across each side of the rail. I can only measure full rail voltage across the PS caps(as it climbs), each side's drain-source has half the voltages which I think is correct (push-pull?)
My other amplifier has 117V or so drain to source on both sides so I think there is something else wrong there, so I do not know what the voltages should be. I am guessing that is the correct rail voltage so each side should be about 60v VDS. I cannot verify the TL494 is good because it is from the amp producing the 117 VDS on both sides but it did so without any delay so i think it is good. I have checked for any bridging or bad joints when I replaced the IC. What else could cause it to build its voltage very slowly like that? It tends to slow down even more after it gets up towards 50v.

TL494 Pin Voltages:
1: 0
2: 4.8
3: 0
5: 1.5
6: 3.6
7: 0
8: 0
9: 0
10: 2.0
11: 1.8
12: 10.2
13: 4.8
14: 8.4
15: 8.4
16: 0

twistedQ 8th July 2012 09:31 PM

The amplifier does settle at a stable 100V rail to rail across the supply capacitors with a Vds of 50V on both sides. It just takes it a minute to get there, it is the only problem with this amp I have left to fix.

twistedQ 8th July 2012 10:54 PM

Have done some more digging and tracing after I un-clamped everything it seems one side of the power supply was trying to pick up the rails because it was getting warm. I thought I had checked the bias voltage before replacing the power supply transistors but it might have been on my other 1200.1 One side's bias voltage was only a couple of mV and the other working side is at 1.5V.
With Q11 and Q35 removed C1 and 2 of the TL494 go up to Vcc and E1 and 2 go to 4V.
This is the first I have had to go that far into the driver other than just replacing the controller but I think I have this one by the tail now.

Now where should I look on my other amp if I have full rail voltage across both sets of the output transistors from drain to source?

twistedQ 10th July 2012 05:36 AM

Does anyone have a good part number for the gain and x-over pots on a kx1200.1 preamp?

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