What's the DC voltage on all of the terminals of the closest optocoupler? Copy and paste the following list and fill in the blanks.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
I did the measurements for both optocouplers 2 different ways.
First, referencing CT
Coupler on the right in previous photo, closer to Right channel (Precisely the one you suggest me to measure)
Pin 1: -0.113
Pin 2: -0.121
Pin 3: 0
Pin 4: -4.002
Pin 5: -3.968
Pin 6:- 3.430
Coupler on the left in previous photo
Pin 1: -0.119
Pin 2: -0.127
Pin 3: 0
Pin 4: 0.003
Pin 5: 0.024
Pin 6: 0.025
Second measurements were referencing amp's general ground
Right
Pin 1: 1.208
Pin 2: 0.007
Pin 3: 0
Pin 4: 0.129
Pin 5: 0.129
Pin 6: 0.129
Left
Pin 1: 1.147
Pin 2: 0.007
Pin 3: 0
Pin 4: 13.87
Pin 5: 14.00
Pin 6: 14.48
First, referencing CT
Coupler on the right in previous photo, closer to Right channel (Precisely the one you suggest me to measure)
Pin 1: -0.113
Pin 2: -0.121
Pin 3: 0
Pin 4: -4.002
Pin 5: -3.968
Pin 6:- 3.430
Coupler on the left in previous photo
Pin 1: -0.119
Pin 2: -0.127
Pin 3: 0
Pin 4: 0.003
Pin 5: 0.024
Pin 6: 0.025
Second measurements were referencing amp's general ground
Right
Pin 1: 1.208
Pin 2: 0.007
Pin 3: 0
Pin 4: 0.129
Pin 5: 0.129
Pin 6: 0.129
Left
Pin 1: 1.147
Pin 2: 0.007
Pin 3: 0
Pin 4: 13.87
Pin 5: 14.00
Pin 6: 14.48
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General likely 'primary' ground.
Didn't you say that the primary and secondary grounds were about equal?
What's the resistance between the primary and secondary grounds? Nothing plugged into the RCA jacks.
Are you using a signal source with a grounded shield?
Didn't you say that the primary and secondary grounds were about equal?
What's the resistance between the primary and secondary grounds? Nothing plugged into the RCA jacks.
Are you using a signal source with a grounded shield?
Fully off and unhooked there is no resistance at all between primary and secondary. OL on the meter. Open.
My source tests were from a car head unit or a frequency generator. Both with sine wave both were exhibiting the same behavior.
My source tests were from a car head unit or a frequency generator. Both with sine wave both were exhibiting the same behavior.
Is the head unit grounded to the same supply as the amplifier?
You should be reading 120 ohms between the grounds.
You should be reading 120 ohms between the grounds.
Yes there’s only 55ohms between amp primary ground and head unit rca shields when RCAs disconnected. Both running from the same power supply.
Re-verified a few things
1. With muting transistors installed;
8~10vDC on speaker terminals.
Lower waveform of right channel not as strong as left channel bot both may have some faults.
Rail voltage 'shifts' by -5vDC on both sides.
2. Without the muting transistors
No significant dc on speaker terminals
Clean waveforms on the scope all the way to clipping.
Rail voltage stays stable.
Amp could likely pass as fixed without the muting circuit.
Amplifier pulls 67amps off the bench on a sine wave just at clipping. Each channel at a 2ohm 12” subwoofer load. One sub per channel NOT bridged.
Re-verified a few things
1. With muting transistors installed;
8~10vDC on speaker terminals.
Lower waveform of right channel not as strong as left channel bot both may have some faults.
Rail voltage 'shifts' by -5vDC on both sides.
2. Without the muting transistors
No significant dc on speaker terminals
Clean waveforms on the scope all the way to clipping.
Rail voltage stays stable.
Amp could likely pass as fixed without the muting circuit.
Amplifier pulls 67amps off the bench on a sine wave just at clipping. Each channel at a 2ohm 12” subwoofer load. One sub per channel NOT bridged.
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What's the resistance from the head unit case to the RCA output shields?
Are you going to leave it as is?
Resistance from primary to secondary ground?
Are you going to leave it as is?
Resistance from primary to secondary ground?
Call me old skool but I'd like to fix this amp as much as I can as long as parts are available. I don't feel right in leaving the muting circuit out. I bet if run in a car it could cause issues.
Head unit to unit's disconnected RCA shields measures 2ohms.
Amp primary to secondary grounds are OPEN. OL. For a brief moment the meter was measuring 20million ohms but then it went OL.
Head unit to unit's disconnected RCA shields measures 2ohms.
Amp primary to secondary grounds are OPEN. OL. For a brief moment the meter was measuring 20million ohms but then it went OL.
Then the head unit shield to the amp ground should read 2 ohms.
Check the 120 ohm resistor near the lower left corner of the last amp photo you posted.
Check the 120 ohm resistor near the lower left corner of the last amp photo you posted.
That resistor is connected between the primary and secondary grounds (which includes the RCA shield ground on most older orion amps). Is it used in some other way in this amp?
That resistor is connected to the following
Right side of the resistor is connected to leg 1 of the mpsa06 between the optocouplers.
Left side is connected to a 1k which is then connected to amp primary ground
Right side of the resistor is connected to leg 1 of the mpsa06 between the optocouplers.
Left side is connected to a 1k which is then connected to amp primary ground
Could it be from the emitter of the A06 to one leg of the thermostat?
If so, it's for regulation.
The primary to secondary ground is open in this series.
Do you read 0 ohms between the amp's RCA shields and the secondary CT?
If so, it's for regulation.
The primary to secondary ground is open in this series.
Do you read 0 ohms between the amp's RCA shields and the secondary CT?
Yes. 0 ohms between secondary and rca shields.
Yes the right side is also going to the thermostat which is measuring closed 0ohms.
For these readings:
Coupler on the right in previous photo, closer to Right channel (Precisely the one you suggest me to measure)
Pin 1: -0.113
Pin 2: -0.121
Pin 3: 0
Pin 4: -4.002
Pin 5: -3.968
Pin 6:- 3.430
Pin 4 should be much lower. The attached diagram may be similar to your amp. Suspect the 22uF cap and the 220k resistor.
Coupler on the right in previous photo, closer to Right channel (Precisely the one you suggest me to measure)
Pin 1: -0.113
Pin 2: -0.121
Pin 3: 0
Pin 4: -4.002
Pin 5: -3.968
Pin 6:- 3.430
Pin 4 should be much lower. The attached diagram may be similar to your amp. Suspect the 22uF cap and the 220k resistor.
Attachments
Its actually a 10uF cap and yes a 220k resistor. I had to lift the 220k to measure it, and its measuring ok. The diode just next to the 220k is also ok. The 10uF cap I actually replaced as I replaced all the 10uF caps on the board because I found one had opened up and was blocking the right channel signal just behind the RCAs yesterday; way before where I am now.
Do you have a full schematic for this or similar amp? I'd like to check everything connected to pins 4/5/6 of the coupler.
Do you have a full schematic for this or similar amp? I'd like to check everything connected to pins 4/5/6 of the coupler.
The only thing I have for these amps are hand-drawn partials.
Tie the small black wire in with the primary ground. Confirm that you read 0 ohms between the RCA shields and the primary ground wire.
What's the DC voltage on both terminals of the 220k ohm resistor?
Tie the small black wire in with the primary ground. Confirm that you read 0 ohms between the RCA shields and the primary ground wire.
What's the DC voltage on both terminals of the 220k ohm resistor?
I've tied the ground together. RCA shields measure 0ohms to both grounds.
On the 220k resistor,
-39.2vDC
-4.32vDC *
Pins of that Octo:
Pin 4. -4.32 *
Pin 5. -4.26
Pin 6. -3.70
* connected
Also I ran a diode check against both Optocouplers. They seem to be OK across pins 4/5/6.
On the 220k resistor,
-39.2vDC
-4.32vDC *
Pins of that Octo:
Pin 4. -4.32 *
Pin 5. -4.26
Pin 6. -3.70
* connected
Also I ran a diode check against both Optocouplers. They seem to be OK across pins 4/5/6.