Orion HCCA 2100 no rail voltage.

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Still chasing that moving target.

This is where I'm at with it now. Pin 4 of the 494 is still a bit high at +0.179v, with no resistor between pins 4 and 7.

All emitter resistors are at 0.000v with amp at idle no speakers hooked to it. However the left side 6491 emitter resistors are at +0.004v with speakers connected, amp at idle. All the other emitter resistors hold at 0.000v with speakers connected.
 
I replaced the 5534 and the DC offset is now:
Right side/no speaker connected +0.065v.
Right side/speaker connected +0.065v.

Left side/no speaker connected -0.055v.
Left side/speaker connected -0.055v.

The DC voltage across the left side 6491 emitter resistors are back at 0.003v. All the rest are at 0.000v. Also noticed the left side output transistors are heating up when the amp is playing. The right side is not.
 
1. Where are you placing the black probe when measuring voltage?

2. Is the 2.7 ohm resistor back in the circuit?

3. Which channel are you referring to as 'right'? Orange or yellow/black?

4. Was the speaker connected when you read 0.003v on the emitter resistors for the 6491s?

5. It's likely that only the 6491s are heating. Is that right?

6. Do they heat at idle with no speaker connected?
 
1. As to where I place the black probe depends on the circuit. Power side - on the negative terminal, audio side - on the RCA shields. For the DC offset it was on the black speaker leads.

2. Yes, the 2.7 ohm resistor is back in the circuit.

3. I'm referring the yellow as the right channel.

4. No, the speaker was not connected when I read 0.003v on the emitter resistors for the 6491s.

5. As to only the 6491's heating up it would make since but I couldn't tell for sure as I have the amp clamped to the heat sink. From what I could tell, it felt like both the 6488's and 6491's on the left side where heating up.

6. They do not get hot at idle with no speaker connected.
 
I believe I may have found what was causing the intermittent DC offset as well as the voltage to be above 0.000v on the left 6491 emitter resistors. The 10uf 50v cap near the 5534. I again replaced all the 10uf 50v caps on the audio side and the DC offset is now -0.043v on the left channel and +0.065v on the right channel and holding. The 6491 emitter resistors are at 0.000v and holding. The DC voltage on pin 4 of the 494 is still on the high side at +0.165v.

However the output transistors are somewhat heating up. Not just the left side but both sides and they are within a few degrees of each other. Not really driving the amp very hard, after about 4 songs the temp on the heat sink next to the clamp bars is reaching 100 degrees Fahrenheit. Not sure if that is normal for this amp but I haven't found other properly functioning Orion amps warming up that much under the same conditions.

Also the amp is intermittently shutting down. Been trying to determine the cause and the only irregularity I found when it does is the voltage on pin 4 of the 494 is above +4.0v DC.
 
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