I made a stupid mistake tonight while trying to start my new PA03 LM4780 chip amp. I now need to know what has been cooked! I made a big error hooking up the secondary from the tranny to the PCB. I mistakenly assumed the center tap were the two inner most connectors, but they weren't. The PCB layout seems a little odd with the center-tap being the two outside connectors instead of the common ground in the middle were the two secondary windings are connected together. Live and learn.
There was no magic smoke, but the tranny immediately started to get very warm - so I knew something was up and pulled the plug. I've since figured out the mis-wiring and reversed the connections, but it still gets hot very quickly, so I fear something has been cooked. My question is, what has been damaged by this fool-hardy mistake? Is the full-bridge rectifier gone, along with possibly the filter caps?
MY AC voltages all checked out fine when measured prior to hooking the tranny up. Any help would be appreciated.
There was no magic smoke, but the tranny immediately started to get very warm - so I knew something was up and pulled the plug. I've since figured out the mis-wiring and reversed the connections, but it still gets hot very quickly, so I fear something has been cooked. My question is, what has been damaged by this fool-hardy mistake? Is the full-bridge rectifier gone, along with possibly the filter caps?
MY AC voltages all checked out fine when measured prior to hooking the tranny up. Any help would be appreciated.
That's my theory too since the tranny starts to heat-up immediately - and it only takes a couple seconds. There's a direct short somewhere. I think I'll replace the rectifier first and see what happens.
Well I replaced the rectifier tonight, wired the secondaries properly, and I had music! Funny how things work right when wired correctly. 🙂 AC voltages checked out, backend DC voltages from PSU were spot on, so I installed the fuses and still no smoke. Good sign. 😀
I connected the speakers, and inputs and voila. Clean undistorted music. I had it playing on the bench for about 20 minutes and noticed the HS was getting rather warm. Not hot, but fairly warm to the touch. I hope my HS is big enough. How hot does a LM4780 chip run? If it becomes an issue I may have to retrofit a fan, or bigger HS on my U-bracket.
Now all I have to do is wait for the enclosure to arrive and get it all installed and put in use.
Rick
I connected the speakers, and inputs and voila. Clean undistorted music. I had it playing on the bench for about 20 minutes and noticed the HS was getting rather warm. Not hot, but fairly warm to the touch. I hope my HS is big enough. How hot does a LM4780 chip run? If it becomes an issue I may have to retrofit a fan, or bigger HS on my U-bracket.
Now all I have to do is wait for the enclosure to arrive and get it all installed and put in use.
Rick
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