I bought the Philips SPC900NC with the intention of converting it to long exposure. I bought it from the Astro Gears guy in Hong Kong. Good service and a fair price, N.B. his website is giving a warning that the inventory is very low now (
http://www.tan14.com/gears.htm).
I have attempted the LX mod as described at
http://www.home.zonnet.nl/m.m.j.meij...Y/spc900nc.htm, based on Steve Chambers work.
I decided to make a few changes to the mod. Using the 4066 chip, 3 unused switches are on the chip, so it seems odd to me to use a manual switch to turn on/off the LX mod (via pin/pad 10). So I added a simple circuit to use the earth connection to the parallel port to drive the pin/pad 10 connection via one of these unused logic based switches.
I have learnt a few things on the way that may interest others making this mod:
1) Many of the links describing web cam mods have gone stale - it can be very frustrating, but since these CCD based webcams are pretty much running out now it probably does not matter much.
2) I removed the microphone, two push button switches (snapped them off) and the LED from the circuit board (LED using soldering iron - but it kind of dissolved/melted and I had to use solder braid to clean up afterwards). I expected these removals would not affect the CCD function and it did not (tested before continuing with the MOD). The switches were removed to improve airflow behind the CCD chip.
3) Since I was not using a magnifying viewer setup, I found the soldering challenging and would never attempt the lifting of surface mount chip pins etc without a magnifier setup. With the SPC900NC the circuit breakouts can be done at the plug/socket connecting the two boards so it is not too challenging but needs a steady hand. The connection to the USB socket pins was still rather daunting, so I examined the board tracks and found that the 5V, 0V pins on the outer edges of the socket were connected to adjacent areas which are much easier to use. For the 5V there is a small square pad that seems intended for access to the supply (perhaps for testing the board in factory). For the 0V, there are 3 pins that can be used, and there is little point trying to get at the inner of them, since they are all clearly connected together on the board close by. The outer one is linked by a track to a surface mount resistor close by. A blob of solder linking the outer pin solder point to the closer edge of the surface mount resister gives plenty of room for a connection and does no harm to the board or circuit.
4) I tested my pin/pad breakouts by reconnecting them using via alligator clips and verifying the camera still worked. I also verified the LX circuits around my 4066 chip (actually I used a 4016 but more about that later) before linking them to the breakout connections. So I was confident it would all work. I broke off the tripod mount point from the case as it used up space in the case and squeezed all the circuits back into the original case before testing again. No luck - a pure black screen showed up in the VLounge viewer. After inspection showed no visible problems, voltage testing showed unusual voltages at both the pin/pad 10 and pin/pad 8/13 (3.6V and 1.6V resp). So I (the next day) removed the LX circuit and reconnected the pads to the pins, i.e. going back to the same test I had performed earlier before I linked in my new circuit. This time the test failed - giving the same black screen. I was really astounded since years of working with electronic components I have found them to be really quite resilient. It seemed from this sequence of events that I must have damaged the CCD camera somehow but I had trouble believing that. So I persisted in looking for another cause. I eventually noticed what was wrong. The springy connector linking the earth for the two boards had been pushed out of alignment presumably no longer providing an earth path for all or part of the CCD chip board. After straightening it out the camera worked again. The spring was probably bent when I squeezed everything back into the case (I should have tested it outside of the case!).
So now I am back to trying again to install my LX circuit. However I had earlier used a 4016 chip instead of the pin identical 4066 chip (since I had the 4016 in my junk box). When the circuit failed to work, I bought a 4066 suspecting it may have been the cause. The 4066 has lower switch "on" resistance so it is preferable in this application. So I guess I should use that now. N.B. the 4016 on resistance is about 600 Ohm compared to the 50 Ohm typical for the 4066 - but the 4016 is faster. Switching in nanoseconds is not important for this application so the 4066 is a better choice.
I'll report later on how things go with my next attempt. And provide more details of the pin/pad 10 switching circuit (pretty obvious though it is).
Alan.