There are several stores selling cheap TDA7293 kits on aliexpress and probably other sites with the note:
That would be fine I guess except that the footprints are not quite compatible; specifically, the 7293 has a dedicated BOOTLOADER pin (12) which drives the bootstrap capacitor, whereas on the 7294, the bootstrap C is driven by the OUTPUT pin (14), and pin 12 is NC.
I received a bunch of these (for an active-crossover system) with PCB layouts that assume a 7293 (bootstrap from pin 12) but the packs included 7294 chips, which I presume means the bootstrap C will not actually charge up, and therefore the chip will probably start clipping at lower than expected power levels. The 7293 I think can bootstrap from the output so it is probably possible to make a board compatible with both chips, but the boards they're selling suit only the 7293, not the 7294.
It could be fixed with a bodge-wire and spot of dremeling, and the kits are still probably reasonable value (similar cost as a single chip shipped), especially if you bin the likely-fake "2200uF 50V 105C" electrolytics and run them off a better DC supply than the little bridge and grossly-insufficient rectifier filter included.
That would be fine I guess except that the footprints are not quite compatible; specifically, the 7293 has a dedicated BOOTLOADER pin (12) which drives the bootstrap capacitor, whereas on the 7294, the bootstrap C is driven by the OUTPUT pin (14), and pin 12 is NC.
I received a bunch of these (for an active-crossover system) with PCB layouts that assume a 7293 (bootstrap from pin 12) but the packs included 7294 chips, which I presume means the bootstrap C will not actually charge up, and therefore the chip will probably start clipping at lower than expected power levels. The 7293 I think can bootstrap from the output so it is probably possible to make a board compatible with both chips, but the boards they're selling suit only the 7293, not the 7294.
It could be fixed with a bodge-wire and spot of dremeling, and the kits are still probably reasonable value (similar cost as a single chip shipped), especially if you bin the likely-fake "2200uF 50V 105C" electrolytics and run them off a better DC supply than the little bridge and grossly-insufficient rectifier filter included.
Which should obviously make you question if the ICs are genuine in the first place, right?
Kits are ok and working, no-brainer for the price.
But you really dont know if chips are 7293/7294 (non genuine of course).
If you are buying chips only from aliexpress, more than 50% are FAKE, empty, not working at all. Dont do it. If you find a working one, u still dont know if you bought 7293 or 7294
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I wanted to repair burned 7293 in parallel amp, and I prefered to buy several kits and pick the 7293's, instead of buying chips from aliexpress (NO NO NO), or genuine chips.
Genuine chips is best, but compromise the whole idea - I would buy a whole working amp for the price of the chips and spend 0 of MY time, to do the extremely expensive (due to parts cost) repair.
But you really dont know if chips are 7293/7294 (non genuine of course).
If you are buying chips only from aliexpress, more than 50% are FAKE, empty, not working at all. Dont do it. If you find a working one, u still dont know if you bought 7293 or 7294
.I wanted to repair burned 7293 in parallel amp, and I prefered to buy several kits and pick the 7293's, instead of buying chips from aliexpress (NO NO NO), or genuine chips.
Genuine chips is best, but compromise the whole idea - I would buy a whole working amp for the price of the chips and spend 0 of MY time, to do the extremely expensive (due to parts cost) repair.
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The layout on the kit boards is Bad, so I've done this:
GitHub - phenidone/tda7293-appnote: PCB for TDA7293/TDA7294 amplifiers, per the datasheet suggestions
There's a schematic PDF and layout PNG for those who don't have kicad for viewing the actual design files. Any comments/input welcome.
GitHub - phenidone/tda7293-appnote: PCB for TDA7293/TDA7294 amplifiers, per the datasheet suggestions
There's a schematic PDF and layout PNG for those who don't have kicad for viewing the actual design files. Any comments/input welcome.
Attachments
I have since ordered all new parts from farnell/e14; they cost me 4x as much for components (excluding PCBs) as what the Chinese kits did.
The supply filter caps (UVZ1H332MHD) alone were more than the complete kits.
I'm currently working up a layout also for a TDA8954 in BTL. If I can fit that into 50x100, I will order them both together on a single panel.
The supply filter caps (UVZ1H332MHD) alone were more than the complete kits.
I'm currently working up a layout also for a TDA8954 in BTL. If I can fit that into 50x100, I will order them both together on a single panel.
Yes the curse of today... either extremely expensive simple parts from a real distributor with minimum order quantity etc. or cheap fake parts .... Hobby people switched to online shopping because that was "easy" and cheaper and cheap = good. This affected the companies that had real shops with real employees, real energy bills and rent to pay. The industry moved over assembly of devices to China as costs were lower and personnel was also cheaper so profit was way higher and those strict environmental regulations could be bypassed as no one seemed to care over there. The small physical shops that were in between and somehow survived slowly have vanished. Since covid the last remaining warriors also have shut down. Now material shortness and energy problems in China where, again for economic reasons, almost everything is produced....
All in all sometimes unforeseen (or was it planned?) developments that have impact on the hobby. Not to mention the industry that has to go to great lengths to obtain simple parts.
Maybe it is a sign that supporting local companies and keep globalism out could be wise choices that after all are in your own personal interest. That "easy & cheap" have become "difficult & expensive" eventually, filling the pockets of a small number of people but none of them in your vicinity. Those in your vicinity have the same issues as you with high(er) energy bills, difficulty to find a job, devices that break down early.....
All in all sometimes unforeseen (or was it planned?) developments that have impact on the hobby. Not to mention the industry that has to go to great lengths to obtain simple parts.
Maybe it is a sign that supporting local companies and keep globalism out could be wise choices that after all are in your own personal interest. That "easy & cheap" have become "difficult & expensive" eventually, filling the pockets of a small number of people but none of them in your vicinity. Those in your vicinity have the same issues as you with high(er) energy bills, difficulty to find a job, devices that break down early.....
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If you are buying chips only from aliexpress, more than 50% are FAKE, empty, not working at all. Dont do it. If you find a working one, u still dont know if you bought 7293 or 7294
.
I was buying fast a2d converters from RS for about £12.
They were $1.50 at Ali Express.
I bought some to see if they worked or not and they were fine.
I continue to buy from Ali but only from same vendor I know was good.
Be careful with power electronics from China as some of the die's are very small compared to the genuine parts.
For sure, not everything from China is fake. Practically all your electronics comes from China anway; the only difference is who is validating which bits of the supply chains.
I have bought a *lot* of cheap Chinese electronics, and probably 95% of it works to-spec. As a gamble, it definitely pays off on average.
I will assemble some extras of my own boards using the 7294's I got in the kits; if they work (which I expect them to!) then they will get used in some other project. Maybe some shed speakers
I have bought a *lot* of cheap Chinese electronics, and probably 95% of it works to-spec. As a gamble, it definitely pays off on average.
I will assemble some extras of my own boards using the 7294's I got in the kits; if they work (which I expect them to!) then they will get used in some other project. Maybe some shed speakers
