Unable to run with +/-15V load. Looking for a schematic of SMPS part, or service manual.
SMPS: P0AA8, PCB325041REVG_03
SMPS: P0AA8, PCB325041REVG_03
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Thanks, now I have it to. Now it's up to you to make it work again. Let us know what you've done. Can be helpfull for others. Good luck ...
I replaced the optocoupler, LM431, PWM. No result. The components seem to be OK. The inductance of the secondary windings for 18/36V is symmetrical for "+" and "-".
When I turn it on, there is a not-so-quiet "zeeepp" sound for about 0.5-1 seconds, and it is possible that the primary winding is faulty. Let's see.
When I turn it on, there is a not-so-quiet "zeeepp" sound for about 0.5-1 seconds, and it is possible that the primary winding is faulty. Let's see.
Do not connect to the mains. Remove the power cord!!!
If I understand wel, when the +/- 15V is loaded the psu will not start.
If so, then try to check the 15V part of the circuit.
Therefore disconnect the rest of the mixer amplifier from connector K7.
Disconnect R103 and R104 at the 18V side.
Connect a 18 - 20V to the +15V circuits and measur the output at K7/1.
Is it +15V then that part is ok.
Do the same with the -15V. Check the polarity of your 18-20V.
Is there a -15 at K7/3?
Yes, then that part is good also.
Now you have to check the circuitry that is connected to the K7 connector.
Do the same again for the +15V and for the +15V.
Maybe there is a short somewhere on antoher board.
Good luck hunting
If I understand wel, when the +/- 15V is loaded the psu will not start.
If so, then try to check the 15V part of the circuit.
Therefore disconnect the rest of the mixer amplifier from connector K7.
Disconnect R103 and R104 at the 18V side.
Connect a 18 - 20V to the +15V circuits and measur the output at K7/1.
Is it +15V then that part is ok.
Do the same with the -15V. Check the polarity of your 18-20V.
Is there a -15 at K7/3?
Yes, then that part is good also.
Now you have to check the circuitry that is connected to the K7 connector.
Do the same again for the +15V and for the +15V.
Maybe there is a short somewhere on antoher board.
Good luck hunting
The problem was in the AMP TDA8954TH. No sound, and finally R31 or R32 4.7 Ohm burned out.
So the SMPS was "ok", except R64/65 R70/71 47 Ohm - they are quite brown.
The "Wzeeeep" sound on startup is present and this is not normal, maybe the transformer was a little damaged. PWM, LM431, optocoupler and one capacitor did not affect this sound.
Power consumption from mains is 41W in total.
One speaker channel has 110mV DC offcet with or without a speaker. In the datasheet there is "SE Operating mode DC Offset −150 .. +150 mV", this is quite a lot.
So the SMPS was "ok", except R64/65 R70/71 47 Ohm - they are quite brown.
The "Wzeeeep" sound on startup is present and this is not normal, maybe the transformer was a little damaged. PWM, LM431, optocoupler and one capacitor did not affect this sound.
Power consumption from mains is 41W in total.
One speaker channel has 110mV DC offcet with or without a speaker. In the datasheet there is "SE Operating mode DC Offset −150 .. +150 mV", this is quite a lot.
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