As you know I am no stranger to the effects of leaked electrolyte. I just cleaned around 494 with acetone and the voltages are now reading:
Pin 1: +2.3
Pin 3: +2.5
Pin 4: +10.5
Pin 1: +2.3
Pin 3: +2.5
Pin 4: +10.5
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Pin 7 is directly tied to ground. It can't read more than a tiny fraction of a volt unless there is a broken trace (not likely).
I connected the jumper. The amp powered up(red light on). The rail voltage across the rectifiers is +42.8 volts. I also monitored for components getting hot, nothing was heating up.
Oh and correction on that about pin 7....It was pin 4 not pin 7. (I corrected the above post).
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Sweeping/rubbing your meter probe on the board around those pins, do you see any voltage?
Confirm that there is nothing connected to each of those pins but a 10k ohm resistor (which goes to ground)
Confirm that there is nothing connected to each of those pins but a 10k ohm resistor (which goes to ground)
Sweep with the probe showed no voltage. Attached are pictures of the trace on the other side of the board. There is a resistor on the top side connected to the trace for pin 1 (the yellow "2" is on top of one of the pins of that resistor in the one photo).
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Sorry for the delay.
On the amp I have here, removing the 6488 did nothing to the voltage on pin 1. Pins 2 and 3 follow pin 1. That's why they all changed. You can reinstall the 6488.
Pin 1 is driven by the protection circuit transistors. Pull them to see if that allows the amp to power up.
On the amp I have here, removing the 6488 did nothing to the voltage on pin 1. Pins 2 and 3 follow pin 1. That's why they all changed. You can reinstall the 6488.
Pin 1 is driven by the protection circuit transistors. Pull them to see if that allows the amp to power up.
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I reinstalled the 6488. Will you show me where the protection circuit transistors are located?
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Sorry that took a minute. I had to clean out my desoldering station...it was clogged.
It did not power up. However the power light did flicker on and off a few times. It did not immediately start flickering after turning on the power supply, it took about four seconds.
It did not power up. However the power light did flicker on and off a few times. It did not immediately start flickering after turning on the power supply, it took about four seconds.
I pulled the jumper since it was powering up with it on. Do you want me to put it back and then check the voltage on pin 1 of the 494?
Jumper is back on. Amp did not power up. Voltage on pin 1 voltage is oscillating between +0.3 and +0.15 would intermittently briefly spike higher up to +1.6 volts.
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