Pioneer Amplifier Repair

[Bromeliad]

Hello everyone, thank you for the existence of this forum.I decided to try to repair a Pioneer SA-540 audio amplifier ( part of an economic system from the 80s ) with almost no knowledge of the subject, but a great desire to learn.

From a careful analysis of all the components on the board I noticed two 'exploded' HICHICON 100uF 25v capacitors (brownish liquid leakage); I don't notice any other damage other than the crumbling of the thermal paste on the transistors. I was present at the moment of his death, faint sound, smell of burning and two blown fuses.

I ask you if replacing the two capacitors could be enough or if I should do other checks and if so which ones. Where can I buy spare parts? Would cannibalizing them from the matching old cassette player be an option? Which soldering iron should I buy to easily remove the solder? Thanks for your time and best regards,

Samuel

 

[Nigel Goodwin]

Those aren't 'exploded' at all, it's simply glue applied to them during manufacture. If it's dead, fuses blown, and smell of burning, then it's almost certain the ourput transistors have failed, and probably other parts as well. The smell is most likely some burnt resistors somewhere, but your picture shows very little of areas of interest.

 

[Bromeliad]

Oh... Thank you so much; i looked more carefully and removed some gunk near a resistor and this is what i found. I guess this means that ther could be damage to the transistors =(

 

[Nigel Goodwin]

The burnt-up resistor looks to be 4.7 ohm, and it's likely that at least the driver transistors and output transistors have also died.

However, the output transistor (in your fourth picture) has dry joints across all it's pins. and this could have caused the problem - but as with all DC coupled amps, you get cascading failures, it's like a chain of dominoes - if one goes lot's of others topple as well.

 

[Les Jones]

It looks like either some liquid has been spilled into the amplifier or the top large electrolytic capacitor marked 38-A has leaked electrolyte (Picture 20230325_172332-jpg). This was probably the start of the sequence of events that caused the fault. You need to find a schematic for your amplifier to help diagnose all the likely components that have failed.

Les.

 

[Nigel Goodwin]

It looks like either some liquid has been spilled into the amplifier or the top large electrolytic capacitor marked 38-A has leaked electrolyte (Picture 20230325_172332-jpg). This was probably the start of the sequence of events that caused the fault. You need to find a schematic for your amplifier to help diagnose all the likely components that have failed.

Les.

It looks more like the same construction glue as on the other capacitors, the most likely cause (as I've already mentioned) is dry joints on the output transistors.

The schematic is easily available from a simple google.

 

[Les Jones]

Hi Nigel, If you look at the close up of the area in picture 20230325_172444-jpg you will see corosion on the cathode end of the diode and the resistors either side of it.

Les.

 

[Nigel Goodwin]

Hi Nigel, If you look at the close up of the area in picture 20230325_172444-jpg you will see corosion on the cathode end of the diode and the resistors either side of it.

Les.

It looks very minor, dry joints on the output transistors is a LOT more serious.

 

[shokjok]

two 'exploded' HICHICON 100uF 25v capacitors

Samuel

I correct your spelling to "Nichicon", whose capacitors are in my inventory.

 

[WesleyJameson]

Hello everyone, thank you for the existence of this forum.I decided to try to repair a Pioneer SA-540 audio amplifier ( part of an economic system from the 80s ) with almost no knowledge of the subject, but a great desire to learn.

From a careful analysis of all the components on the board I noticed two 'exploded' HICHICON 100uF 25v capacitors (brownish liquid leakage); I don't notice any other damage other than the crumbling of the thermal paste on the transistors. I was present at the moment of his death, faint sound, smell of burning and two blown fuses.

I ask you if replacing the two capacitors could be enough or if I should do other checks and if so which ones. Where can I buy spare parts? Would cannibalizing them from the matching old cassette player be an option?Vscomodapk
Which soldering iron should I buy to easily remove the solder? Thanks for your time and best regards,

Replacing the two capacitors is a good starting point, but it's also important to check the surrounding components for any signs of damage, such as burnt or discolored resistors or transistors. You can use a multimeter to check if the components are functioning correctly. In addition, it would be a good idea to visually inspect the solder joints on the board to ensure there are no cold solder joints, which can cause intermittent or faulty connections.

 

[gilshehbaz9]

Hello everyone, thank you for the existence of this forum.I decided to try to repair a Pioneer SA-540 audio amplifier ( part of an economic system from the 80s ) with almost no knowledge of the subject, but a great desire to learn. From a careful analysis of all the components on the board I noticed two 'exploded' HICHICON 100uF 25v capacitors (brownish liquid leakage); I don't notice any other damage other than the crumbling of the thermal paste on the transistors. I was present at the moment of his death, faint sound, smell of burning and two blown fuses. I ask you if replacing the two capacitors could be enough or if I should do other checks and if so which ones. Where can I buy spare parts? Would cannibalizing them from the matching old cassette player be an option? Which soldering iron should I buy to easily remove the solder? Thanks for your time and best regards, Samuel

It's great that you want to learn about audio amplifier repair! If you've spotted two damaged capacitors and some old thermal paste, start by replacing those capacitors with the same values, which you can buy from electronics stores. Cannibalizing from a similar device might work if the parts are in good condition. For soldering, a 30-40W adjustable soldering iron is suitable, along with solder, desoldering tools, and a soldering iron stand. Remember safety—unplug the amplifier and discharge any stored energy before you start. It's a learning journey, so be patient and seek help from forums or experienced folks if needed. Good luck!