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+--- Thread: ProtoDAC TDA1387 X8 project (/showthread.php?tid=5531)
RE: ProtoDAC TDA1387 X8 project - hifinet - 11-28-2023
(11-28-2023, 07:41 PM)Nutul Wrote:(11-28-2023, 06:06 PM)hifinet Wrote: Usually the primary leads are reversed
I am confused here... how can a transformer have its leads "reversed"?!? We're not talking DC here, guys...
The amp is push-pull with the positive half of the wave produced by one output tube and the negative half from the other. The transformer primaries are connected to the plates (anodes) of the output tubes (the third lead is from the midpoint of the primary winding and connects to B+ or DC high voltage). If you reverse the primary leads, this will cause a polarity inversion in the secondary output.
RE: ProtoDAC TDA1387 X8 project - hifinet - 11-28-2023
Gerber for ProtoDAC PCB Version 2d
Above is the link to the latest Gerber file for ProtoDAC PCB Version 2d from 11/12/2023 (12-Nov-2023). It adds 3.5mm lead spacing for caps C3 and C4, which allows the specified Panasonic EEU-FR1A102L to properly sit on the PCB.
RE: ProtoDAC TDA1387 X8 project - Tim Curtis - 11-28-2023
Nice, I'll update the protoDAC section at moodeaudio.org later today.
RE: ProtoDAC TDA1387 X8 project - hifinet - 11-29-2023
Thank you, Tim.
Also, thank you for updating the assembly instructions. Could you please change steps 3 and 4 to 1 and 2? Add "Clean flux from the top of the PCB with flux remover." to the end of the new step 2.
RE: ProtoDAC TDA1387 X8 project - Tim Curtis - 11-29-2023
Sure. I'll update it later this afternoon.
RE: ProtoDAC TDA1387 X8 project - kLOkUIS - 11-30-2023
(11-22-2023, 03:42 PM)hifinet Wrote: I am not sure. The 130k resistors would generate a much higher than normal voltage at the analog outputs. I wouldn't think this would damage the module. Play a 50Hz 0dB sine wave file and measure the DC and AC voltages at pins 6 and 25 of the module with a DMM. Also, be sure the I2S resistors (R1-R3) are correct.
Thank you for the information. I should have followed your advice because maybe I would have been wiser now. But I desoldered all components (except the chip) and started on a fresh pcb.
I’m happy to report that it works beautifully now.Though I can’t give an answer if the wrong resistors kills the 8x TDA1387. It might have been a soldering error, or a bad chip from the beginning
Kind regards, Louis
RE: ProtoDAC TDA1387 X8 project - hifinet - 11-30-2023
Thank you for the follow up.
Of all the modules I have tested, I have yet to find a completely dead module. The most common flaws are one bad chip or one channel out on one chip.
RE: ProtoDAC TDA1387 X8 project - Patolog1964 - 12-01-2023
Hi Hifinet.
I also have a module that drops out irregularly. It manifests itself in the way that the SS voltage starts appearing irregularly at the output.
I've tried everything possible, but the only thing that works is the cooling spray.
if I refrigerate it, it will last another day or two.
I would easily buy a tested module from you, but the problem is that I don't know what would be paid for customs duties, etc. I'm from Europe, the Czech Republic.
I have ordered two more modules. I hope I will be lucky.
Best regards, Roman
RE: ProtoDAC TDA1387 X8 project - hifinet - 12-01-2023
Hi Roman,
That behavior could be explained by a bad solder joint between the pin and module PCB. If it involves both channels, it could be either pin 5 (ground) or pin 28 (5V). First, inspect the joints with a magnifier, looking for cracks in the solder or separation from the PCB pad. If you see a problem, you can target that connection. Reflow the solder. If the solder has lifted from the pad, you might try adding some liquid flux, which can help solder to adhere to the PCB pad.
RE: ProtoDAC TDA1387 X8 project - Patolog1964 - 12-01-2023
Thank you very much for your answer.
Re-soldering the pin was the first thing I did. From the side of the circuit board, as well as the module. I personally suspect the calibration smd capacitors connected to pin 7. The module is soldered, so I would have to pull it out using a vacuum cleaner. If I measure individual capacitors to ground on pin 7, they all show me an ESR value of around 30 ohms, which seems a lot to me.
Do you have any experience of replacing them with others, possibly with a higher value? It is true that if I pull them out, there is not much space. But it could be solved by soldering the top of the module directly to pin 7 against the ground.
Today I tested trying to connect a raspberry to the Cd player module with TDA1541A. Everything works as it should.
Thanks for the advice.
Best regards, Roman