Thanks for the help!
There should not be a ground loop, as I did not change anything from working to non-working. I will make pictures Wednesday, when I'm back at work. I will try separate power supply tests then as well.
as promised some pictures of the build. Could be neater, I know ;)
The basic setup is quite easy. Power in goes into a soft power-on by diy-audio. From there to the two transformers and then into the symasym power section.
Input is directly soldered onto the pcb, output goes through the speaker protection on the black beauty.
Too much work today, I will disassemble and inspect tomorrow. Maybe an input wire has come loose or the ground-cable on the pcbs? I hope nothing is really damaged...
One thing I noticed further:
All four leds are on as soon as I plug in power. As soon as I unplug them, the two LEDs on the left PCBs side stay on, while the right side LEDs go out immediately. Could this be an indication for a short on the right pcb side?
sorry for the message spam, but I can't edit my posts after some time.
I did some more measurements today with help of a colleague. I was mistaken with my DC output measurement (was measuring after speaker protection...).
My amp has -23VDC on the speaker output, measured against GND! :eek:
Our current idea is, that one of the transistors is defective, what do you think?
I donīt think that one of the transistors must be defective. Probably the Transistors (including the Drivers) on the negative rail are not on their working point. About 10V are drop down at the power transistors.
Thanks for the info, any idea on how to debug this? Would it be better to keep it mounted to the heatsink to make measurements or should I disassemble and look for bad solder points?
such a beautiful design
can I have Gerber and drill files?
is it too bad to use ST semiconductors 5200 complementary?
Help needed :/
my work kept me too busy these past weeks, I finally found time to do some measurements yesterday.
Setup was with bridged input and a 4ohm high-load resistance on the output (didn't want to burn my speaker). All measurements were taken in DC against Ground.
Do these values make any sense to you? My initial guess is, that Q1 or Q2 is defective, since there is dc voltage already present in the input path? I'm no electrical engineer though.
All help is highly appreciated!
so I have been told by PM, that I am asking too much of you. I know, fixing someone else's mistakes is a pain in the ***, especially, if that someone is a new member. Maybe I was also not clear enough, I am not asking for someone to give me the solution (although that would be nice), but rather hints/ideas on how to proceed.
At this point I could throw the whole thing into the trash and quit, but I choose to try and fix it anyways. I will post progress here anyways, maybe at some point someone has an idea or hint.
Current state of progress:
* I have unmounted the defective amp from the case and test it by itself.
* I have checked again, that not concact is between the heat sink and other components (there is none).
* I have measured all passive components in the input path for correct values (in reference to the functioning channel). They seem ok.
I am currently trying to focus on the problem of dc voltage at the input side. When measuring with open input there is ~2VDC at the input connector. This (so far my theory) is then further on amplified by the power transistors. From my understanding, the voltage can only come from Q1 or Q2. I have therefore ordered a new set of 2SK170 and will replace them in the coming days.
Also, I have thought again about the reason for this issue. My current idea here, is that when mounting everything into the case, I have shorted the input and output side, thus giving an amplified signal into the input and overloading it.
Ideas/Comments? Should I change Q3/4 as well, while I'm at it? Or am I completely on the wrong path? Unfortunately the pcbs are not sold anymore, or I would just build a new one...
As always, help of any kind is highly appreciated.
nice living Project i have found here. I plan to build my first diy amp and i live near Berlin Germany. I hope i am right here. is this ok if i ask for pcb layout files? I want to etch my own boards at home, dont Need a bigger amount or Long waiting time for boards from China
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