TDA7293 dies easily from static (how to fix?) - Page 1
Forum section: electronics / beginners

author: justin66
author_rank: Regular Contributor
timestamp: January 16, 2024, 05:00:59 pm
content: hello, i have built an amplifier using this board, it works fine but my stupid chair always charges me to high static voltage how do i prevent this? i tried adjusting volume (touched heatsink first) and small static was all it took. how can i prevent this in the future? the plan for future is make a case and everything this is just temporary. weird but TDA7294 seems to hold to all those static touches haha

author: coromonadalix
author_rank: Super Contributor
timestamp: January 16, 2024, 06:12:50 pm
content: simply put ditch the chair, anything generating static must me eliminated, clothes, non anti static gloves, carpetry etc...change clothes washing stuff like put anti static sheet in the dryer or change brands ...when all physical stuff / problems are resolved, the next step is the design, not the other way

author: justin66
author_rank: Regular Contributor
timestamp: January 16, 2024, 06:29:41 pm
content: thanks for the reply, i will address the static chair problem, what can i implement into a design to make it more static proof as well?

author: Manul
author_rank: Super Contributor
timestamp: January 16, 2024, 07:03:37 pm
content: So which exact point of the circuit received the ESD? It could be that your IC is a fake one. If it is not, I very hardly believe that it can be killed by ESD, especially in circuit and with heatsink around. In my opinion more realistic is indirect damage to the IC - something else in the circuit is affected by ESD, some voltage rises, kills the IC. That sort of thing.

author: srb1954
author_rank: Super Contributor
timestamp: January 16, 2024, 07:20:08 pm
content: Quote from: justin66 on January 16, 2024, 06:29:41 pmPut an earth bonding strap from the heatsink back to to the supply common or, better still, put the whole circuit in a grounded metal case with the heatsink electrically bonded to that metal case.With ESD protection issues the important thing to consider is where the ESD current, which can be many amps, flows when seeking a path back to ground. You should endeavour to have a low impedance path from any likely contact point back to ground so that the ESD currently flows preferentially through that path rather than through your electronics. Since ESD currents can have very short rise times, sometimes under 1ns, it is also important to minimise the inductance in this return path so as not to develop excessive voltages across any stray inductances.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 17, 2024, 03:28:31 am
content: are yur supply lines once rectified and filtered are near the ic limits, meaning when you power up the amp the voltages spikes and toast your ic,assuming it's a genuine chipit seems your toroid is self made ??

author: MarkT
author_rank: Frequent Contributor
timestamp: January 17, 2024, 02:17:16 pm
content: Firstly I'd recommend a metal case and provide a solid mains earth to this - I can see a twin-wire mains lead bottom left.Secondly the transformer secondary pigtails have lost their sleeving - they are bare wire! Fix this before you accidentally short them and fry your transformer.Once you have it safe and in an earthed box I doubt you'll have static issues.

author: justin66
author_rank: Regular Contributor
timestamp: January 17, 2024, 07:53:43 pm
content: Quote from: Manul on January 16, 2024, 07:03:37 pmthe heat sink witch is not connected to anything, silicone pads, plastic washers, most likely not fake, the supplier usually gets it from mouser on bulk, i also verified the back of the ic shape witch indicates the genue part. also 10 euros a pop.

author: justin66
author_rank: Regular Contributor
timestamp: January 17, 2024, 07:57:42 pm
content: Quote from: srb1954 on January 16, 2024, 07:20:08 pmhard to achieve. my apartment only has 2 prongs neutral and live wires, the best i can prob do is either use a radiator or neutral wire as a ground but i would rather not use neutral even tho its supposed to be PEN. atm i sprayed my chair with an anti static spray, used 1/3 of the can at least, and i will ground myself to PC case before i touch amp. i wonder if metal case will help this at all coz heat sink is supposed to be a floating just like case will be

author: justin66
author_rank: Regular Contributor
timestamp: January 17, 2024, 08:00:30 pm
content: as a test it is on lower voltage branch on transformer giving me plus and minus 31.5V DC (63Vdc combined) i also have wound transformer to make it 43VDC (86v combined) for increased power if i need to. initially i calculated this voltage for 4ohms but i think i will stick to the 31v for now.

author: justin66
author_rank: Regular Contributor
timestamp: January 17, 2024, 08:05:03 pm
content: Quote from: MarkT on January 17, 2024, 02:17:16 pmthe problem is i dont have any earthing in my house besides the radiator haha. this transformer i just wound and this mess is just as a temporary test kinda setup to see if its going to work and have any issues. i will insulate them for sure but i dont leave amp on unattended. if this wont work i will have to resort to buying something off the shelf. i hate that transformer sometimes does the sound i guess some bigger inductive load increases the sound a little bit