Hi,
I took a parts unit of classe ca5300 amp. Its a 5 channel 300w amp. initially it was in protection mode because one channel had blown outputs. While doing the fault finding I accidentally (forgot that rail voltages were still there with unit off) plugged in PS wiring and sparks came up and blew that amp. Changed couple 82v zenar diode, MJD243/MJD253 pairs and all outputs. Over the period I have blown 7 pairs (10 transistor per pair pair). Each amp board has 5 pairs of 2sa1294 2sc3263 output transistors. Changed all including pre-driver mosfets. Most parts are still obsolete so have been careful to buy from reliable sources. Initially 2 channels were working and now one of them also blew. rail voltages and test points per Classe were correct and it biases to 1mv. Its a weird procedure but maintained the 0.3+/- mv. When I play music or sometimes just while waiting for biasing the outputs blow and unit goes into protection. So in all the unit can be biased and within around 10 mins the outputs blow. I even changed emitter resistors which measured fine. I am not able to find the root cause and not willing to blow more transistors which are obsolete. The last board that blew was had the original outputs and LME49810 chip. Not that I am doubting the purchased parts but if this went out then the root cause might be different. Now the common denominator is power supply. Today morning I measures the rail voltages and once I get 87vdc I monitored for 10 mins. It went to 87.5vdc and come back to 87.3vdc. I think this variation is acceptable. Then I removed the power supply board and checked the bridge rectifier which hardly fail. I didnt make full test but if the BR blew it wont give DC voltages that are close. Finally I see Four 5600uf 100v caps bank per rail which measures 17900uf. I think its just lower than 20% which should be 22400. I removed one cap and it measures 4600uf instead of 5600uf. ESR being 0.03 ohm. Anyway I think its at the lower end of 20%. I am not sure if this could be the root cause. I am lost so looking for some guidance on how to determine the root cause. I almost gave up but I know on this forum there are many experts who can guide me. Thanks in advance.
I took a parts unit of classe ca5300 amp. Its a 5 channel 300w amp. initially it was in protection mode because one channel had blown outputs. While doing the fault finding I accidentally (forgot that rail voltages were still there with unit off) plugged in PS wiring and sparks came up and blew that amp. Changed couple 82v zenar diode, MJD243/MJD253 pairs and all outputs. Over the period I have blown 7 pairs (10 transistor per pair pair). Each amp board has 5 pairs of 2sa1294 2sc3263 output transistors. Changed all including pre-driver mosfets. Most parts are still obsolete so have been careful to buy from reliable sources. Initially 2 channels were working and now one of them also blew. rail voltages and test points per Classe were correct and it biases to 1mv. Its a weird procedure but maintained the 0.3+/- mv. When I play music or sometimes just while waiting for biasing the outputs blow and unit goes into protection. So in all the unit can be biased and within around 10 mins the outputs blow. I even changed emitter resistors which measured fine. I am not able to find the root cause and not willing to blow more transistors which are obsolete. The last board that blew was had the original outputs and LME49810 chip. Not that I am doubting the purchased parts but if this went out then the root cause might be different. Now the common denominator is power supply. Today morning I measures the rail voltages and once I get 87vdc I monitored for 10 mins. It went to 87.5vdc and come back to 87.3vdc. I think this variation is acceptable. Then I removed the power supply board and checked the bridge rectifier which hardly fail. I didnt make full test but if the BR blew it wont give DC voltages that are close. Finally I see Four 5600uf 100v caps bank per rail which measures 17900uf. I think its just lower than 20% which should be 22400. I removed one cap and it measures 4600uf instead of 5600uf. ESR being 0.03 ohm. Anyway I think its at the lower end of 20%. I am not sure if this could be the root cause. I am lost so looking for some guidance on how to determine the root cause. I almost gave up but I know on this forum there are many experts who can guide me. Thanks in advance.
Hi there
Have you checked the LME49810 chip ?
Front what I read it is taken out if output devices short out.
Look for other threads in this group about the CA5300
Good luck
Have you checked the LME49810 chip ?
Front what I read it is taken out if output devices short out.
Look for other threads in this group about the CA5300
Good luck
Yes I did that and replaced them. But as I mentioned the original that was working before also blew. Am bit lost on root cause