Notfe that you must isolate the regulators but when you have done that the LM4780 doesn't have to be isolated.
Regulators are insulated. For the LM4780 i only used nonconductive thermal paste.
I got mine with the board from sjostromaudio. The replacement chip is going to be from ebay --> 1x LM4780 Originale NATIONAL / TI TEXAS Stereo 60W Mono 120W Audio Amplifier DIY | eBay
Just ordering a couple of them now from farnell.
Make sure that the heatsink is not connected to anything. When the LM4780 is mounted the heatsink will be connected to your negative raw voltage through the backplate of the IC.
Did you have +- 35 V or something?
BTW: I can guarantee that the chip was OK when you got it from me.
Did you have +- 35 V or something?
BTW: I can guarantee that the chip was OK when you got it from me.
Yes I had +-35V before mounting the heatsink. After I mounted the heatsink I installed the Voltage regulators and the LM4780TA. What's curious to me is, that also the relays are not switching. How long does the timer take to switch the rleays?
I just measured again +-32V.
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I'm really wondering why i have -29,6V at TP4. Could this really be a damaged chip or anything else?
Are you sure you succeed when it comes to the feedback network, both in values and in soldering? Was the chip hot without any load connected? No blown fuses?
There is 29VDC on your output. I guess that's the reason the output relays are not switching.
Do you have approx. 2-3 amps from each rail, without blowing the fuses? Nothing else is hot?
When I check your pictures, it seems that you have quite much tin and not so well molten. On the component side I see that the tin hasn't flown up through the holes. This doesn't need to be a bad thing.
When I check your pictures, it seems that you have quite much tin and not so well molten. On the component side I see that the tin hasn't flown up through the holes. This doesn't need to be a bad thing.
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Just to be sure. The recommendation is to replace the chip?
Does anyone have measurements for the pins of the chip before installing it? I would like to make sure that the problem doesn't originate from a defect opamp, transistor, ...
The guy in this thread might have had a similar problem like me --> http://www.diyaudio.com/forums/chip-amps/129485-i-had-problems-my-lm4780.html
Does anyone have measurements for the pins of the chip before installing it? I would like to make sure that the problem doesn't originate from a defect opamp, transistor, ...
The guy in this thread might have had a similar problem like me --> http://www.diyaudio.com/forums/chip-amps/129485-i-had-problems-my-lm4780.html
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I think i will just measure the voltages before soldering the new chip, to make sure everything is correct. Mostly i can only measure the v+ and v- voltages and the input form the opamps.
-> http://www.farnell.com/datasheets/1994371.pdf
Did i mention that i hate unsoldering stuff. Especially if it has more than 2 pins 😉 Not giving up on this board.
-> http://www.farnell.com/datasheets/1994371.pdf
Did i mention that i hate unsoldering stuff. Especially if it has more than 2 pins 😉 Not giving up on this board.
after i removed the 4780 to see if there's something odd with the voltages i realized that the relays went on as desired. i will get a replacement chip soon and will give it another try.
here's my measurements
I've added it to the album
here's my measurements
An externally hosted image should be here but it was not working when we last tested it.
I've added it to the album
If you just want to replace the chip you can cut all pins and then it will be easier to clean the holes. Try also to analyze what when wrong like solder bridges, short circuits in bad places etc.
Unsoldering was fine. Chip is already removed since yesterday. I was able to remove it without cutting the legs. now waiting for a replacement chip. farnell didn't accept my order, since i don't have my own company.
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here's my measured voltages on the chip pins without installed chip. what is curious to me is the 0.3V where i should have 0V.
ground when measuring with the multimeter was the contact between the large electrolyte condensators.
i could imagine that the voltage regulators are creating a offset to the ground of the power supply when the chip is not installed. but maybe this was the issue what caused my problems.
http://imgur.com/8K3J6yD
ground when measuring with the multimeter was the contact between the large electrolyte condensators.
i could imagine that the voltage regulators are creating a offset to the ground of the power supply when the chip is not installed. but maybe this was the issue what caused my problems.
An externally hosted image should be here but it was not working when we last tested it.
http://imgur.com/8K3J6yD