Hi folks. Long story but keeping it short. I have a CA5300 that was blowing fuses. I took it to repair and see my luck. Figured out that one channel's amp board had all the outputs shorted. Below is summary
CH1 - While amp was off, I didnt realize that wired from PS still had 80+ volts and it sparked. I then discharged the caps and then connected it. I then noticed the 253 transistor was chipped off. No burn smell through. I replaced it from other board. Swapped this from other board and when I switched it on a loud bang and before any smoke, I immediately switched it off. With these amps there is no way I can use a DLB or Variac as the protection circuit doesnt engage if it sees that I have a DLB (100V bulb) or a variac.
CH2 - I powered it on but had the magic smoke. Later I see there is a 82V zenar doide and adjacent 253 transistor was smoked. I used parts from this board to CH1 and waiting for the parts to arrive.
CH3 - Working fine
CH4 - This was the original channel that had blown outputs. So I swapped the A1294/C3263 pair of outputs. Total of 5 pairs. This time, I used all the outputs from CH2 and the amp started to work and thought I had fixed it. The sound was not fully clear when I was testing. I increased the volume and boom. went into protection mode and same original issue. It was blowing fuses. All 5 pairs of outputs went shorted within 2 mins of running. This also caused the two big CL80 thremosister (maybe a bigger one not sure) to smoke but I switched the unit off on time.
CH 5- Working fine.
I checked all the caps. For each board there are 9 of 100uf 100v. They all are measuring 89 to 92uf with .45 ohm ESR. I will be changing all the caps and will see. For the people who worked on these amps, what were the probable components that failed. The LME49810 is unobtainable and I don't know how to check if the chip is working or not. I am trying to source 10 pairs of A1294/C3263 and K-amps member was kind enough to confirm that he might have them.
So key question is what would be the cause for the pop/bang from amp board and smoke. Even if I manage to find 10 pairs, how do I validate if the amp board would work without burning any components. Any guidance that helps me. Thanks
CH1 - While amp was off, I didnt realize that wired from PS still had 80+ volts and it sparked. I then discharged the caps and then connected it. I then noticed the 253 transistor was chipped off. No burn smell through. I replaced it from other board. Swapped this from other board and when I switched it on a loud bang and before any smoke, I immediately switched it off. With these amps there is no way I can use a DLB or Variac as the protection circuit doesnt engage if it sees that I have a DLB (100V bulb) or a variac.
CH2 - I powered it on but had the magic smoke. Later I see there is a 82V zenar doide and adjacent 253 transistor was smoked. I used parts from this board to CH1 and waiting for the parts to arrive.
CH3 - Working fine
CH4 - This was the original channel that had blown outputs. So I swapped the A1294/C3263 pair of outputs. Total of 5 pairs. This time, I used all the outputs from CH2 and the amp started to work and thought I had fixed it. The sound was not fully clear when I was testing. I increased the volume and boom. went into protection mode and same original issue. It was blowing fuses. All 5 pairs of outputs went shorted within 2 mins of running. This also caused the two big CL80 thremosister (maybe a bigger one not sure) to smoke but I switched the unit off on time.
CH 5- Working fine.
I checked all the caps. For each board there are 9 of 100uf 100v. They all are measuring 89 to 92uf with .45 ohm ESR. I will be changing all the caps and will see. For the people who worked on these amps, what were the probable components that failed. The LME49810 is unobtainable and I don't know how to check if the chip is working or not. I am trying to source 10 pairs of A1294/C3263 and K-amps member was kind enough to confirm that he might have them.
So key question is what would be the cause for the pop/bang from amp board and smoke. Even if I manage to find 10 pairs, how do I validate if the amp board would work without burning any components. Any guidance that helps me. Thanks
