The point is, commercial Li-Ion batteries are not "naked" cells but always have electronics associated with them to avoid overcharging or deep discharging. Otherwise they'd never be safe. As a DIYer, you typically have access to the bare cells only.
As for C6/C7, see here. In a nutshell - unless you have actual problems with the negative regulator, .22µF should be fine.
As for C6/C7, see here. In a nutshell - unless you have actual problems with the negative regulator, .22µF should be fine.
Hey guys, I was testing my O2 as per nwavguy's guide. All test were fine until I came to this step:
Check The Raw DC Voltages – With amp turned on, no batteries installed, and no headphones, the DC voltages should measure approximately as shown in the diagram to the right (click for larger or right click and open in a new window) with the negative DMM probe connected to the negative terminal of BT1 (ground) as above, It’s important to verify the voltage shown on D3 and D4 are within 0.1 volt of each other but opposite polarities. For example if the banded end of D3 is 17.5 volts then the un-banded end of D4 should be 17.4 to 17.6 volts. If there a greater difference, something is likely wrong. See the Troubleshooting Section.
(was on AC power, no batteries. Switch was on. U1 to U4 were all socketed.)
I measured D3 and D4 correctly (around 24 and opposite polarity), and P8 and P4 of U4 correctly as well (around 11.7 and opposite polarity), as well as D1 and D5 correctly (12 and opposite polarity).
However, as I was removing my probe from D1, my hands slipped and contacted against the metal tab of U6. There was a audible crackling sound. I went back to check all the 3 pairs of voltages as mentioned above, and now they are ALL off.
D1 now measures +15.6V, D5 is -12V, D3 +17.5V, D4 is +20V (the number kept flashing on this one), P4 on U4 is -11.7V and P8 on U4 is +16V.
After remeasuring everything. I switched everything off. I realised that C2. C3. C4, C5, U5 and U6 were extremely hot.
I have no ideas where to go from here, and I would appreciate anyone's kind help!
Check The Raw DC Voltages – With amp turned on, no batteries installed, and no headphones, the DC voltages should measure approximately as shown in the diagram to the right (click for larger or right click and open in a new window) with the negative DMM probe connected to the negative terminal of BT1 (ground) as above, It’s important to verify the voltage shown on D3 and D4 are within 0.1 volt of each other but opposite polarities. For example if the banded end of D3 is 17.5 volts then the un-banded end of D4 should be 17.4 to 17.6 volts. If there a greater difference, something is likely wrong. See the Troubleshooting Section.
(was on AC power, no batteries. Switch was on. U1 to U4 were all socketed.)
I measured D3 and D4 correctly (around 24 and opposite polarity), and P8 and P4 of U4 correctly as well (around 11.7 and opposite polarity), as well as D1 and D5 correctly (12 and opposite polarity).
However, as I was removing my probe from D1, my hands slipped and contacted against the metal tab of U6. There was a audible crackling sound. I went back to check all the 3 pairs of voltages as mentioned above, and now they are ALL off.
D1 now measures +15.6V, D5 is -12V, D3 +17.5V, D4 is +20V (the number kept flashing on this one), P4 on U4 is -11.7V and P8 on U4 is +16V.
After remeasuring everything. I switched everything off. I realised that C2. C3. C4, C5, U5 and U6 were extremely hot.
I have no ideas where to go from here, and I would appreciate anyone's kind help!
Okay, I'm not entirely sure how to ensure consistent voltage polarity in the reading, but here goes:
C4 was +17.5V, C5 was around +19.6V (number kept flashing) (I kept probes in the same orientation, aka when board was flipped upside down, black was on the left contact and red was on the right contact for both C4 and C5)
C6 was +17.2V and C7 was -11.95V (I kept the probes in the same orientation across C6 and C7 as well)
Components heated up real quickly.
Consistent polarity isn't really necessary; it's the absolute values that are important at this stage. But, keeping the black probe connected to the ground point will give the proper polarity.
Your circuit has virtually the same voltage into the positive regulator as it has at the output of the regulator. Replace it and repeat post #2968.
Your circuit has virtually the same voltage into the positive regulator as it has at the output of the regulator. Replace it and repeat post #2968.
Okay. The negative regulator U6 measures 12V, which I think is okay. However, the positive regulator U5 measures nothing at all for both input and output voltage. So obviously something before the regulator is spoilt. How do I determine which component is down?
Thanks for the speedy response so far, sofaspud, really really appreciate it
Thanks for the speedy response so far, sofaspud, really really appreciate it
I'm becoming more puzzled. You replaced U5 but still got no regulated output, and now the input voltage is missing?
What is the rating for your transformer? You wrote "C5 reads 25.6V, C4 reads 26.3V" which could put a dissipation strain on the voltage regulators, though it shouldn't with the O2 turned off. Remove the batteries if they are installed just to be sure, and to help isolate the power supply circuit. Check the D3 & D4 diodes. After that, remove C2, test the regulator input and output voltages, then put it back in and repeat for C3, C4, and C5 one at a time. If you haven't already, double check that there are no solder bridges shorting the power supply. Or a PCB trace that became a (opened) fuse when you had that little shorting accident. A good inspection and test of the dozen or so components in the ps should make the problem jump out at you.
What is the rating for your transformer? You wrote "C5 reads 25.6V, C4 reads 26.3V" which could put a dissipation strain on the voltage regulators, though it shouldn't with the O2 turned off. Remove the batteries if they are installed just to be sure, and to help isolate the power supply circuit. Check the D3 & D4 diodes. After that, remove C2, test the regulator input and output voltages, then put it back in and repeat for C3, C4, and C5 one at a time. If you haven't already, double check that there are no solder bridges shorting the power supply. Or a PCB trace that became a (opened) fuse when you had that little shorting accident. A good inspection and test of the dozen or so components in the ps should make the problem jump out at you.
Okay. Across D3 is 26.7V, across D4 is 26.1V. Across C3 and C5 is also 26.1V, whereas C2 and C4 are also 26.7V. I also measured the + end of C4 into the input pin of U5, the positive regulator, which also measured 26.7V. The puzzling part is that the voltage across the input and the ground pins of U5 is zero.
U6 does not have this problem. It measures 26.1V from input to ground, and 11.9V from output to ground.
I just replaced U5. Could it be that the new U5 is defective?
U6 does not have this problem. It measures 26.1V from input to ground, and 11.9V from output to ground.
I just replaced U5. Could it be that the new U5 is defective?