Looks ok grounding com-nc but stil slow drain will happen because of 10uF and resistors values, delay is about 0.2s using those values, I would change booth 10uF with 100nF for example.
1) will do, provided I have one with such a high Voltage,
2) I'd have to order some to be able to see the difference, I used them in the past, but they now live in my daughters sub amp,
3) currently 2,3mV DC, with the subwoofer connected.
Regards, Jan.
I have a couple of TDA7293 underway, so I'm checking the two spare boards to meka sure they are indeed not working.
Just reconnected the one with the hum; measured over 9V DC on the speaker output, hence the hum...
I can remove the chip from this board.
On with the second.
Regards, Jan.
Just reconnected the one with the hum; measured over 9V DC on the speaker output, hence the hum...
I can remove the chip from this board.
On with the second.
Regards, Jan.
X rated cap will be the best.
In post #62 I see you have a 1µF X2 cap, I think it's too high a value for across the switch, but you could connect that across the 12V transformer primary and see if that gets rid of the power off 'thud'.
I think that will disconnect the speaker instantly.
However, I suspect that the turn off "thud" is caused by the power switch arcing or the magnetic field of the 12V transformer collapsing.
Put a switch on the DC side to control the relays will confirm it.
To my surprise, this second one plays without a hitch..., as the delay on the mains switching off is still active, this one also produces a very audible thud when I power down.
Maybe the sparking noise was the chip protesting against the 30V, I used initially, no idea really, on 12V it works, so this one will be modified to get the mute function to work as it should, the Savan way
Regards, Jan.
Maybe the sparking noise was the chip protesting against the 30V, I used initially, no idea really, on 12V it works, so this one will be modified to get the mute function to work as it should, the Savan way
Regards, Jan.
I'll keep looking for a X-rated cap, but in the mean while do I put the 1µF X2 cap pre, or post the switch on the primary?
BTW: I took the test set-up, thud and all, to a friend, for whom I've designed and build a 6th Order Isobaric sub and tested it there. Works like a charm and only needed the volume knob in the 9 or 10 o'clock position to keep up with the small stereo satelites. TV-sound system.
Regards, Jan.
Hi Savan,
As I'm currently using a 2 x 12V toroid to power the TDA7294, do I need to use different values for the capacitors and resistors?
The plan is to cut the traces and solder the alternative values in place.
I can use 2 x 24V, but this means wiring two 12V toroids to get 24-0-24V AC. Stacking two toroids on the test board will make it a bit lopsided, as they are 225 VA toroids...
Regards, Jan.
Sorry, I think it is still too high of capacitance across the primary as well, it could cause problem when power on. Please just ignore it.
As a side note: the isobaric sub uses two 4 Ohm speakers wired in parallel. The TDA7294 doesn't seem to mind and has been playing all afternoon without any noticable heat build up, the heat sink remained at ambient temperature.
I only realized it had been playing on the 2 Ohm load when I got home. Normally, the sub is powered by a stereo amp, one half for each speaker...
Regards, Jan.
I only realized it had been playing on the 2 Ohm load when I got home. Normally, the sub is powered by a stereo amp, one half for each speaker...
Regards, Jan.
Savan, please take a look and let me know if I can power this up.
I made the cuts with a Ø1 mm milling cutter in my Dremel and checked if the traces were cut properly with the multi meter.
Soldered on the jumper wire and removed the 10uF from the top; this was not the nicest job, as I have big hands and there isn't a lot of room, I modified a wooden washpeg to get a grip on the capacitors...
The 100nF came out of my spare box and are decades old, but still measure properly (99,8 nF).
I didn't have a 6.2K at hand so I used a 5.1K with a 1K, which wasn't a bad solution given the space underneath the board.
The relay bridges the cut in the powersupply when the amp is powered up and should cut it when the 12V transformer powers down.
Regards, Jan.
I made the cuts with a Ø1 mm milling cutter in my Dremel and checked if the traces were cut properly with the multi meter.
Soldered on the jumper wire and removed the 10uF from the top; this was not the nicest job, as I have big hands and there isn't a lot of room, I modified a wooden washpeg to get a grip on the capacitors...
The 100nF came out of my spare box and are decades old, but still measure properly (99,8 nF).
I didn't have a 6.2K at hand so I used a 5.1K with a 1K, which wasn't a bad solution given the space underneath the board.
The relay bridges the cut in the powersupply when the amp is powered up and should cut it when the 12V transformer powers down.
Regards, Jan.
Hi Chris,
I also have a number of these 100nF capacitors:
I can't find for which Voltage they are suitable though, size is 20 x 16 x 8,2 mm legs are 0,8 mm thick.
Usable/suitable?
Regards, Jan.
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Crap...
I just mounted the modified board back onto the heatsink, reconnected the wiring.
Did a last visual check between my pictures and those Savan posted and saw that I have switched the positions of the 3.3K and and the 6.8K resistors...
Fortunately I had not powered up anything.
I'll remove the board and switch the resitors to the correct places.
Stupid me...
Regards, Jan.
I just mounted the modified board back onto the heatsink, reconnected the wiring.
Did a last visual check between my pictures and those Savan posted and saw that I have switched the positions of the 3.3K and and the 6.8K resistors...
Fortunately I had not powered up anything.
I'll remove the board and switch the resitors to the correct places.
Stupid me...
Regards, Jan.
Another thing: I still have the 2200uF capacitor and diode in place, theoretically, this should not have any effect on the Savan mod?
Just let me know, as I already have to remove the TDA board, again...
Regards, Jan.
Just let me know, as I already have to remove the TDA board, again...
Regards, Jan.
Jan, resisitor values is diferent for 12V power supply! The mod I have done is for power supply of 40V since in that time when I wrote that you had 40V power supply! For 12V power supply as you using now, you need to replace 3.3k with resistor values between 15k-22k and 6.2k replace with resistor values between 30k-40k ! Capacitor voltage after divider is no more than 6V even its less, so you can use for example capacitors with declared votage of 12V with no problem. Use this to calculate resistor divider for Vout 5V https://www.digikey.fr/en/resources/conversion-calculators/conversion-calculator-voltage-divider , Vout must be between 4V to 6V with no problem so chose resistor value you have at home. If you using 40V power supply than my mod should be used wothout any changes.
2200uF and diode can stay.
2200uF and diode can stay.
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Merci pour repondre Savan,
I'll keep the values you calculated for the 40V version for when the TDA7293, I ordered, arrive.
I'll try to play with the calculator, but I have to admit, I don't fully understand what I'm supposed to do to make it work.
Tomorrow I'll remove the low values and replace them with what I have available, within the range you specified and let you know if and how this works.
Regards, Jan
I'll keep the values you calculated for the 40V version for when the TDA7293, I ordered, arrive.
I'll try to play with the calculator, but I have to admit, I don't fully understand what I'm supposed to do to make it work.
Tomorrow I'll remove the low values and replace them with what I have available, within the range you specified and let you know if and how this works.
Regards, Jan
Sorry Jan, I can't confirm the voltage rating, I wouldn't put it on 230V mains voltage if it were me!
Please refer to #84 post, my suggestion is to add a switch on the DC side to experiment. If there is a "pop" when opening, add those film cap to the switch and see if that works (since it is at about 17VDC).
Its simple, you have 22k in series and you need to add paralel resistor value to make resitor divider for get 5V out for stdby. Also you have two resistors in series 33k+10k=43k and you need to calculare paralel resistor value to get 5V for mute pin. So that way on the link I have provided enter Vin value e.g. if you using 12V power supply enter 12 or if you using 40V pover supply enter 40. For R1 enter 22k or 43k and calculate to get aroung 5V for booth mute & stdby. No need to be excatly 5V out but between 4 to 6 volts is ok, even 7V is ok but don't do less than 4V since 3.5V is a treshold value for mute&stdby=OFF , better is having 4V and up, do it by looking into what you have from resistors in your home and use those values for R2 in calculator
Hi Savan,
So if I understand it correctly, when using 12V, the 6,2K has to be 4,7K (6.26V) and the 3,3 has to be 22K (6V), in oder to get both values over 5V.
I'l start changing out the values, but I'll wait for you to confirm (or not) before I apply power.
Regards, Jan.
So if I understand it correctly, when using 12V, the 6,2K has to be 4,7K (6.26V) and the 3,3 has to be 22K (6V), in oder to get both values over 5V.
I'l start changing out the values, but I'll wait for you to confirm (or not) before I apply power.
Regards, Jan.