Thank you for another great video, I like that you explain a bit about devices and what you would expect to measure etc..... it's helpful "back in the head" clues for someone like me that never formally learned much about electronics.
Power supplies are the unsung heroes of any repair bench. Last one I bought was a triple output one; didn't need it but it was in nice shape and I convinced the owner to sell it cheap rather than haul it around to the area hamfests for the next few years...
@@EriksElectronicsWorkbench I'm building my repair bench and learning all I can about electronics repair. However, at 58 it might too darn late to do anything worthwhile. I'd really like to be able to competently repair audio gear because of the joy such gear brings to most folks. For the past 19 years I've been repairing welding power supplies and related equipment, some their PCBs also. Thanks for the work you do. All the best, Kevin
awesome thanks, because the voltage delivery is split between 2 stages (1 - 15V and 15 - 30V) would a final voltage regulation test for the 2nd stage voltage value be warranted? ie 24V no load full load Cheers
The same voltage regulation circuit is used no matter if the low or high voltage range is in use. It's just changing the voltage applied to the bridge rectifier. After the rectification everything is the same. However off camera I did test across the full voltage range because the power dissipation in the series pass transistors varies depending on output voltage and I wanted to make sure my replacement transistors worked ok (they did).
29:14 50W extra power dissipation means that the cooling system must be able to handle 50W more. So it's not just like "50W extra nothing wrong with that".
What was meant is the the transistors are not being worked as hard to dissipate power near their specified max limit. It would be like replacing a resistor with one of a higher wattage rating. The component isn't being stressed as much. Nothing was modified in a way to make more power actually dissipated on the transistors. Depending on load current they can run fairly hot.
Yes it worked fine for 20 years. I think the power switch was on its way out and I didn't realize it. The fuse holder plastic was old and disturbing it probably made its contacts become intermittent. The fuse was never touched in 20 years. The actual failure was the transistor.
Thank you for another great video, I like that you explain a bit about devices and what you would expect to measure etc..... it's helpful "back in the head" clues for someone like me that never formally learned much about electronics.
I'm glad the videos on my channel are helpful for you. I appreciate the compliment. Thanks for taking time to watch!
Power supplies are the unsung heroes of any repair bench. Last one I bought was a triple output one; didn't need it but it was in nice shape and I convinced the owner to sell it cheap rather than haul it around to the area hamfests for the next few years...
Same here, plenty of power supplies have made it to the bench but you can never have too many.. lots of variations in voltage, current and features.
Very Well Done! Thx for the vid! I suspect the power transistor failure took the power switch and fuse holder with it.
Very nice! Is great to see the channel is growing!
Great diagnostics, Eric. Love your style of working. Thanks for sharing with us.
Guter Job. Abo gegeben. Gruss aus Europa.
Another repair class taken in. Thanks Erik!
Glad you found the video helpful!
@@EriksElectronicsWorkbench I'm building my repair bench and learning all I can about electronics repair. However, at 58 it might too darn late to do anything worthwhile. I'd really like to be able to competently repair audio gear because of the joy such gear brings to most folks. For the past 19 years I've been repairing welding power supplies and related equipment, some their PCBs also. Thanks for the work you do. All the best, Kevin
@@welderfixer never too late to get into electronics repairs :) audio component repair is a great area to do repairs, I enjoy that as well.
Another scrap heap rescue, nice one Eric.
I wonder whether the SMPS units of today will attract such loving attention in future years!!! 🤣
Thanks for the great video.
awesome thanks, because the voltage delivery is split between 2 stages (1 - 15V and 15 - 30V) would a final voltage regulation test for the 2nd stage voltage value be warranted? ie 24V no load full load Cheers
The same voltage regulation circuit is used no matter if the low or high voltage range is in use. It's just changing the voltage applied to the bridge rectifier. After the rectification everything is the same. However off camera I did test across the full voltage range because the power dissipation in the series pass transistors varies depending on output voltage and I wanted to make sure my replacement transistors worked ok (they did).
Surely I was not the only one expecting the two transistors to be 2N3055 ?
You were not !
Certainly a popular choice in many power supplies, power dissipation is a bit lower they'd be pushing it in this application.
First thing to check
maybe want to kill time
29:14 50W extra power dissipation means that the cooling system must be able to handle 50W more. So it's not just like "50W extra nothing wrong with that".
What was meant is the the transistors are not being worked as hard to dissipate power near their specified max limit. It would be like replacing a resistor with one of a higher wattage rating. The component isn't being stressed as much. Nothing was modified in a way to make more power actually dissipated on the transistors. Depending on load current they can run fairly hot.
This thing sure had a lot of problems, are you sure it was working before?
Yes it worked fine for 20 years. I think the power switch was on its way out and I didn't realize it. The fuse holder plastic was old and disturbing it probably made its contacts become intermittent. The fuse was never touched in 20 years. The actual failure was the transistor.