If R54 has -37v then the base of Q22 will have -37volts meanig the amplifier will have serious DC voltage on J12.
Please confirm.
Please confirm.
If U5 pin 7 has +40volts on it, the voltage will be blocked by C33/34 so will not affect R54 that MUST be at zero volts.
Where are you putting your volt meter probes to measure these voltages?
Where are you putting your volt meter probes to measure these voltages?
When you measured and replace C35, did you meaqsure R68 to make sure the ground link has not been broken ...
No DC voltage on J12.
Strange story. if the minus of the multimeter on the chassis and withis red I try to check the voltage on q22, the motor of the volume knob turns on, and if I check the collector, the amplifier enters into protection
Strange story. if the minus of the multimeter on the chassis and withis red I try to check the voltage on q22, the motor of the volume knob turns on, and if I check the collector, the amplifier enters into protection
As R68 has been damaged, without working on the amplifier, I cannot help anymore.
Good luck but I think it must go to a competent repair shop.
Good luck but I think it must go to a competent repair shop.
Let me see if I get this right:
1. you have +40V on pin1 of CN4
2. You have -37V on R54
The -37V on R54 can only come from the lower end of the LTP, so Q19, Q20 and the circuit around Q23 and Q25 would be suspect. Disconnect the base of Q23 to rule out that feedback circuit.
The +40V can only come from the other side of the connector, as R54 is already on -37V.
I'd say you have 2 different problems on two PCB's.
1. you have +40V on pin1 of CN4
2. You have -37V on R54
The -37V on R54 can only come from the lower end of the LTP, so Q19, Q20 and the circuit around Q23 and Q25 would be suspect. Disconnect the base of Q23 to rule out that feedback circuit.
The +40V can only come from the other side of the connector, as R54 is already on -37V.
I'd say you have 2 different problems on two PCB's.
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Oh dear!
Which transistor collector ... SAP15NY or PY?
Do you know how to read a schematic?
The collector of each transistor is either +ve rail SAP15NY or -ve rail SAP15PY, it is possible with a power supply fault to have +40volts everywhere if the -ve 40volt supply is disconnected. Have you checked that ...
You don't make much sense and are not giving any actual details of the voltages or the fault.
First you say the protect relay is not operational then you say it is, you then give some very obvious incorrect voltages that point to a broken ground. This is suggested and you later confirm this fact.
I would like to help but I cannot see the amplifier on my bench, so guess work is the best anyone can do.
Without actual details, I and I am sure, most everyone else is at a loss.
C35 blocks DC between Pin 1 of Con 4 and R54. From what you are saying, there is 40volts on either side .... +ve or -ve you do not disclose.
If there is 40volts on both sides of the capacitor then the common denominator here is a broken ground point.
From what I can tell, you either haven't or don't know how to check these points.
Basics;
Power supply has both + and - voltages. Are they present ...
The ground points are connected to the common power supply connection, are they connected ...
Con4 has 40volts on pin1, what about pin2 ...
Be specific with components; U3 is the PNP and U4 NPN output transistor, both are not the same and are known to fail internally.
There are two rails; +45volt and -45volt ... be specific.
Q21 and Q22 have aproximately the same voltages on each pin; is that correct.
These simple fault finding pointers help with diagnosis.
Which transistor collector ... SAP15NY or PY?
Do you know how to read a schematic?
The collector of each transistor is either +ve rail SAP15NY or -ve rail SAP15PY, it is possible with a power supply fault to have +40volts everywhere if the -ve 40volt supply is disconnected. Have you checked that ...
You don't make much sense and are not giving any actual details of the voltages or the fault.
First you say the protect relay is not operational then you say it is, you then give some very obvious incorrect voltages that point to a broken ground. This is suggested and you later confirm this fact.
I would like to help but I cannot see the amplifier on my bench, so guess work is the best anyone can do.
Without actual details, I and I am sure, most everyone else is at a loss.
C35 blocks DC between Pin 1 of Con 4 and R54. From what you are saying, there is 40volts on either side .... +ve or -ve you do not disclose.
If there is 40volts on both sides of the capacitor then the common denominator here is a broken ground point.
From what I can tell, you either haven't or don't know how to check these points.
Basics;
Power supply has both + and - voltages. Are they present ...
The ground points are connected to the common power supply connection, are they connected ...
Con4 has 40volts on pin1, what about pin2 ...
Be specific with components; U3 is the PNP and U4 NPN output transistor, both are not the same and are known to fail internally.
There are two rails; +45volt and -45volt ... be specific.
Q21 and Q22 have aproximately the same voltages on each pin; is that correct.
These simple fault finding pointers help with diagnosis.
Ok Thank you very much.
Yes Victory.
the previous owner confused two connectors.
CN2 and CN4 and therefore burned out U5. now I have connected everything correctly and the amplifier is working.
Only balance pot is very bad.
Yes Victory.
the previous owner confused two connectors.
CN2 and CN4 and therefore burned out U5. now I have connected everything correctly and the amplifier is working.
Only balance pot is very bad.
CN2 has 3 pins ... CN4 has 2.
Switch cleaner/lubricant will probably help with that.
EML200F | Electrolube 200 ml Aerosol Contact Cleaner | RS Components followed by
SGB200DR | Electrolube 200 ml Aerosol Contact Grease for Contacts, Thermoplastics | RS Components to help lubricate the contacts.
Switch cleaner/lubricant will probably help with that.
EML200F | Electrolube 200 ml Aerosol Contact Cleaner | RS Components followed by
SGB200DR | Electrolube 200 ml Aerosol Contact Grease for Contacts, Thermoplastics | RS Components to help lubricate the contacts.