Category Archives: Electronics

Onkyo TX-SR706 Troubleshooting

A friend of mine has an Onkyo TX-SR706 receiver that had issues where the HDMI ports didn’t work.  All he gets through them is green artifacts.

After checking the interwebs, I see that there is a pretty common failure mode in these where the caps on the voltage regulators for the DAC board go bad, and lead to issues.  After probing the regulators with my Rigol DS2072A oscilloscope, I found a regulator with a lot of noise on the output indicating a bad decoupling cap.

Put a good cap across it, and viola, all good.  Decided to just go through and replace all the voltage regulator decoupling caps since I was in the equipment.

Here is a video.

LT-1303-5 with new inductor

 

Based on some ideas in the eevblog forums, I replaced the TDK inductor I used in the first videos with a Sumida RCH-855np.  The sumida specifically says…

Applications
• Ideally used in Printers, LCD TV, DVD, Copy Machine, Mainboard of the compounding machines etc. as DC-DC Converter inductors.

Since the TDK data sheet was a bit ambiguous and stated it was for “Power lines” there was a theory that the TDK may have actually been a choke.  Turns out the results show pretty much the same performance.  I was unable to get above 67% efficiency.  I would really like to see someone do better with this chip on video.


I think my next step will be to but the Adafruit kit for the minty boost, which uses the LT1302 chip in its design.  I am curious to see the results on a professionally designed pcb with a similar chip.

Followup to the LT1303-5 DC to DC Boost Converter

Per  many recommendations by the forums users over at eevblog.com, I made a few modifications to the boost converter circuit.  I increased the size of the output filter cap, and reduced the length of the conductors.  I picked up 5% additional efficiency but still fall short of the 80+ percent in the data sheet.

LT1303 Efficiency dataRevised for 17mA out.

 

LT1303-5 two cell to 5V Boost converter supply

In this video I put together a small circuit to test out the LT1303-5.  I am not getting the efficiency numbers in the data sheet.  See the attachment below for the figures I recorded.  Granted I don’t know what Im doing, so if you spot the issue, please let me know… and be gentle.  Thx, JZJ

 

 

LT1303 Efficiency data

LT1303-5 boost regulator datasheet