Looks like the cap was across a power transistor, is that right? If so you might want to check the transistor. Anything else connected to that node? If so you might want to check that too.
You stated that the amplifier worked for a while. We cannot therefore rule out that the capacitor tail had not actually touched the board, but some wire or connector had been disconnected while moving the board. A common fault, as example, are cracked solders on big wire or power connectors pads.
On the worst case scenario, the high voltage supply has been shorted to a lower voltage circuit. A semiconductor device has been damaged or a non self-resetting protection device on the power supply circuits (such as a fusibile resistor) opened up. They may be on a completely different position on the circuit board. This would prevent the amplifier to turn on. A fault finding with the multimeter is then required, as stated on post #5. I would start by checking if the standby supply of the microcontroller is present. You may find useful a cheap component tester such as the LCR-T4, it will identify many components such as 3-terminal semiconductor devices with proprietary markings and check if the capacitors are still good. You may also use it to see if the original main filter capacitors can be still reused for experimental purposes or as "better than nothing" replacement parts.
On the worst case scenario, the high voltage supply has been shorted to a lower voltage circuit. A semiconductor device has been damaged or a non self-resetting protection device on the power supply circuits (such as a fusibile resistor) opened up. They may be on a completely different position on the circuit board. This would prevent the amplifier to turn on. A fault finding with the multimeter is then required, as stated on post #5. I would start by checking if the standby supply of the microcontroller is present. You may find useful a cheap component tester such as the LCR-T4, it will identify many components such as 3-terminal semiconductor devices with proprietary markings and check if the capacitors are still good. You may also use it to see if the original main filter capacitors can be still reused for experimental purposes or as "better than nothing" replacement parts.
Hi Mark , thank you.
I’m presuming it’s this transistor ( blue arrow) the yellow arrow is the capacitor.
I’m presuming it’s this transistor ( blue arrow) the yellow arrow is the capacitor.
Hi , thanks for your input, I do have a peak component tester . Would you mind telling where the micro controller is and how I test it please?
Kind of looked like it to me. Can you read schematics at all? If so, find the cap on the schematic and see what other parts connect to it.
I think I’ve read the schematic correctly, it’s a little confusing being dual mono ( left or right )
Yellow markings show the offending cap and the transistor it’s linked to .
Yellow markings show the offending cap and the transistor it’s linked to .
Where does the connection that goes straight down to a horizonal trace/node go? Is that the negative rail, -70v? Which end of the cap got shorted? Kind of looks like it was the side connected to the transistor collector and the negative rail, is that right? If so, what did it short to, ground? Or something else?
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You've encircled the wrong cap in the second photo.
But can you make another photo of the same section of the layout on the good channel, so we can compare how tracks run and how to fix the missing pad for the lifted cap.
You might have to turn the amp 180° to get the 2SA-side in view.
It's not clear yet what these caps are doing there, and so very close to the heat sink. Thankfully they're tropical (105°C) grade.
There is only one fuse ( 4 amp ) which I have replaced, unless there is another component that acts as a fuse ?
It is decoupling capacitor, negative rail to ground, close to output transistors to cut the inductance of tracks.
Picture shows (I could be wrong there, not showed shorted points) the ground node connected to emitter.
It would be short connection negative side and very possibly defective one or more output transistors.
If so, said that amp is not powering, broken fuse would pointed exactly that case.
Other possibility, processor watchdog, detecting anomaly not powering power section. Bot only guessing, not familiar with that unit.
P.S.
New fuse can be burned in milliseconds in case of short
circuit.
Picture shows (I could be wrong there, not showed shorted points) the ground node connected to emitter.
It would be short connection negative side and very possibly defective one or more output transistors.
If so, said that amp is not powering, broken fuse would pointed exactly that case.
Other possibility, processor watchdog, detecting anomaly not powering power section. Bot only guessing, not familiar with that unit.
P.S.
New fuse can be burned in milliseconds in case of short
circuit.
If the negative rail touched any transistor 'points,' have you tested any and all possibly affected transistors with a DVM diode check function, and or with some other component tester?
Ah, check the transformers primary, sometimes the fuse is built in.
Output transistors should be checked as well.
Output transistors should be checked as well.
Guys I’m a builder and fixer of properties.
I thought components could only be tested once removed?
The new fuse is fine , there are no clicks or anything when I power it on
I thought components could only be tested once removed?
The new fuse is fine , there are no clicks or anything when I power it on
Measuring device, ac voltage. Primary 230V, secondaries 2 x something like 40 - 75V.
But it looks like heavy repair. I would suggest professional service,
But it looks like heavy repair. I would suggest professional service,