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Old Apr 16, 2013, 01:42 PM
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Originally Posted by timetec View Post
Hi everyone - It's been a good while since I last posted, so I thought I'd share a mod that will eliminate the annoying 'buzzing' sound and/or video artifacts, as the battery starts to run down on your #11 camera. This issue was addressed of course with the launch of the #16, but to the best of my knowledge at the time of posting, still remains a problem with #11.

As a bonus to this relatively simple fix, your battery life should be extended by around 15% (in tests), adding 6 minutes or so to your current recording time using a good 250mAh LiPo cell
The cause of these sound and video issues centres around the stock 3.3V voltage regulator fitted on the front (USB socket side) of the PCB. The IC is a 5-pin SOT-25 device marked 4A2* - the * is the batch code and will be a letter such as B D or C etc. The regulator fitted is a TOREX XC6204332 - datasheet HERE

Technical stuff :

There are two major problems with this factory fitted regulator : 1/ It has a maximum current rating of 150ma, but typically the device has to deliver over 100ma continuously and subsequently gets hot, wasting precious power. 2/ It has a high dropout voltage of 200mv (0.2V) rising to over 300mv at 100ma - this has a marked effect on the available recording time of the camera.

The replacement, a Texas Instruments TPS73633DBVT - datasheet HERE has a rated output current of 400ma, limited at 800ma. As a result it runs cool, disipating very little power.
In contrast, the dropout voltage of the TI regulator is specified at 75mv. However in practise it's much lower than this - I measured a miniscule dropout of just 26mv with a 100ma load.
The NMOS output stage and clever high frequency 4Mhz charge-pump make it a very efficient, low noise and reliable replacement for the original regulator.

I can't recommend this modification highly enough and at a cost of around 65 pence / $1 excluding shipping, makes it a very worthwhile and satifying mod. You may even be able to get a free sample from the TI website.
Yes, the regulator can be a bit fiddly to swap out if you're not used to handling surface mount devices, but after disconnecting the battery you can wrap the whole PCB in tin foil, neatly cutting out a small square hole where the regulator is. This will prevent solder splashes getting onto the PCB, as well as acting as a perfect anti-static sheild for the board. By far the easiest way to remove the IC, is to surround it in flux paste and heat the plastic package directly until the solder on all five legs melts. It can then be gently lifted off the board with a pair of fine-tipped tweezers.

You will notice from the TOREX datasheet that pin 4 is not used - NC (no connection), while the TI device uses this pin for a noise reduction capacitor (NR).
It appears that the the camera manufacturers decided to fit a 10nf capacitor to the PCB to cover all eventualities when sourcing 'equivalent' components.
If required, the value of this capacitor, circled in yellow on the third photo, can be increased in value from 10nf to 100nf to acheive a noise level of below 30 microvolts using the TI device specified here.

Have fun - Richard

I made this mod to my second gen #11, the one after the initial batch, which allows you to install no timestamp firmware. A quite early batch.
The PCB differs a little though to the photos that have been uploaded.
It does not have a capacitor or diode above and to the left of the voltage regulator. Here is the PCB with the LDO removed.
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However the mod fixed the low voltage buzzing in sound the battery life got shorter instead of better.
Before the mod the battery lasted for 37mins recording @10.8K bitrate @4K cluster size formatted card @ Rel 1 firmware.
After 29mins 30 sec the buzzing was present to the video.

After the mod the battery lasts for 29mins 50sec. Exactlly as it is with the stock voltage regulator with no buzzing.
So I lost 7mins of recording time actually.
Hopefully the video is still saved if the battery gets exhausted.

By the way. I found easier to cut the chip`s legs with a sharp surgical blade, just being careful not to cut any traces on the PCB.
Then it was very easy to unsolder the remaining individual legs and solder back a fresh TI TPS73633DBVT with the help of a pen soldering iron and a ERSA 0832UD/SB tip. Using this tip I could even desolder and solder back a 0402 resistor.

Ohh, for anyone insterested the capacitor size is 0402, as it is with almost the majority of the SMD components there.

A good mod but unfortunately is not good for my version of PCB as it seems.

Modifications to reduce audio interference

This mod, the resistor and the capacitor, did not worked either. One camera has white noise if ambient audio level is low or it is quite/noone speaks, etc. If it is then the camera starts increasing the white noise level but if there is a sufficient audio level then it keeps the white noise level low.
Like it is trying to maintain a sound level to a given value or something, either with actual sound or white noise.

PS. I am very happy with both of my early #11`s. Both running Release 1 "exposure control" firmware, capturing at 10.7K bitrate with very sharp image and no focusing problems either if it is a close or distant capture.
And I DO like the colors as mostly I shoot personal videos (my kid) and vacation stuff.
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