Hi glt,
I had a 5w 15ohm resistor in my parts kit. I placed it across output of placid and voltage was steady at 5.5. As suggested that resistor got very hot in few minutes.
Per Russ's suggestion,I measured the resistances across the caps in AVcc module-
C1 measured at 18k and C2 was in megaohm range. I hope measured the right ones.
Brian,
I will try to get the pictures of the transistors on placid. If I don't get clear pictures, is it OK to post the numbers on the devices?
Thanks for all the help guys, I hope I will get it up and running soon
Suresh
I had a 5w 15ohm resistor in my parts kit. I placed it across output of placid and voltage was steady at 5.5. As suggested that resistor got very hot in few minutes.
Per Russ's suggestion,I measured the resistances across the caps in AVcc module-
C1 measured at 18k and C2 was in megaohm range. I hope measured the right ones.
Brian,
I will try to get the pictures of the transistors on placid. If I don't get clear pictures, is it OK to post the numbers on the devices?
Thanks for all the help guys, I hope I will get it up and running soon
Suresh
Hi,
Can you check the power supply voltage without any connection. You found that the resistance of the Buffalo was 15k. Sometime the LM78xx do not put voltage out on less there is a load. Since the resistance is 15k and dividing 5.5 volts/15K this give you a low load. Or you can put the resistor in parallel with the Preamp and see what happen.
Can you check the power supply voltage without any connection. You found that the resistance of the Buffalo was 15k. Sometime the LM78xx do not put voltage out on less there is a load. Since the resistance is 15k and dividing 5.5 volts/15K this give you a low load. Or you can put the resistor in parallel with the Preamp and see what happen.
That means it is almost certain the Placid is not at fault. That is how I built my Placid. After completing it, I let it sit with a resistor for many hours to make sure the supply is solid.
Try lowering the voltage of the Placid to 5V or even 4.5V. The opamp of the AVCC supply specs out at around 5.5V (if I remember correctly)
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Removed the AVCC module and tried powering up, none of the leds lighted up.
I was very careful on adjusting placid per instructions on initial power up as the instructions are explicit the voltage on power up can exceed 5.5 easily.
I tried adding the loading resistor per another suggestion but the problem remains
I was very careful on adjusting placid per instructions on initial power up as the instructions are explicit the voltage on power up can exceed 5.5 easily.
I tried adding the loading resistor per another suggestion but the problem remains
Hello Russ,
Placid was adjusted with buffalo board not connected to give 5.45v. As per glt's suggestion tried the resistor load instead of dac and placid holds the voltage steady at 5.45v with 15 ohm resistor load.
LEDS are placed in socket holders as I intended them mount on the front panel of the dac case. I removed and connected them to battery supply with resistor and they work fine.
I have a Salas shunt board that puts out 5v at 200ma designed for the digital section of the TDA 1541 dac and I have tested it on my TDA1541 Dac.Can I use it to power the buffalo board and see whether it works?
Placid was adjusted with buffalo board not connected to give 5.45v. As per glt's suggestion tried the resistor load instead of dac and placid holds the voltage steady at 5.45v with 15 ohm resistor load.
LEDS are placed in socket holders as I intended them mount on the front panel of the dac case. I removed and connected them to battery supply with resistor and they work fine.
I have a Salas shunt board that puts out 5v at 200ma designed for the digital section of the TDA 1541 dac and I have tested it on my TDA1541 Dac.Can I use it to power the buffalo board and see whether it works?
Yes, very helpful.
The problem seems to be that you have a short after or within the 1.2V VDD regulator.
This could mean a couple of things.
1) Perhaps a short between components pads. Check around C12 and C15 on the bottom of the board.
2) Could also be a ESD damaged chip.
3) Least likely is a dead VREG, I say this because the current it could ever see is limited by the Placid itself.
Also closely inspect all of the components and DAC pins connected to that net. For example C21 and C22.
The problem seems to be that you have a short after or within the 1.2V VDD regulator.
This could mean a couple of things.
1) Perhaps a short between components pads. Check around C12 and C15 on the bottom of the board.
2) Could also be a ESD damaged chip.
3) Least likely is a dead VREG, I say this because the current it could ever see is limited by the Placid itself.
Also closely inspect all of the components and DAC pins connected to that net. For example C21 and C22.
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I carefully looked for any visible shorts both near the reg and Dac and under the board. Pictures attached. I could not see any problem.
Looks like the chip may be damaged or reg it self may be shorted. Unfortunately I do not have SMD capabilities. Can I send the board for repair to Twisted Pear?
Looks like the chip may be damaged or reg it self may be shorted. Unfortunately I do not have SMD capabilities. Can I send the board for repair to Twisted Pear?
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Have you tried feeling the chips to see if any of them are getting hot when the buffalo is powered on? If you're loading the placid so hard that the voltage rail drops to 1.2 volts a lot of current is going somewhere.
I've had a similar problem where I blew an ASRC chip. On power on, the 3.3veg was loaded down and the ASRC chip itself got very hot. It didn't take a genius to figure out what had gone wrong.
If there is a short internal to one of the components, it might heat up also. However if it's a solder bridge somewhere they probably wont.
I've had a similar problem where I blew an ASRC chip. On power on, the 3.3veg was loaded down and the ASRC chip itself got very hot. It didn't take a genius to figure out what had gone wrong.
If there is a short internal to one of the components, it might heat up also. However if it's a solder bridge somewhere they probably wont.
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