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Old 04-03-2010, 08:36 PM
alanfvic (Alan)
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SPC900NC LX mod in progress

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.

Last edited by alanfvic; 04-03-2010 at 08:47 PM.
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  #2  
Old 04-03-2010, 11:20 PM
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kinetic (Steve)
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Alan,

great write up, I hope it goes well.
As for the broken links, I see you found Matthias' page, his is the one
I followed years ago. Another good one is Jools Palmer's page here:
http://www.palmer895.btinternet.co.uk/spc900.htm

Mine might also be a broken link too. My old Tel$tra page isn't up
anymore and I had a few details about my mods and homemade housings
on that. I'll eventually get it back up somewhere online.
Mine works through a hybrid cable that I made which has both
parallel and USB control lines in it with no crosstalk or bad data.
I made the connections all standard so I could run all of my
different webcam mod cameras with this same cable. I used a DB9
for the pinouts.

I've done a few 900NC mods now and they have all gone well.
It's a very easy mod compared to the nerve wracking pin lift mods
I did years previous.
I've got one that is peltier cooled in an aluminium housing. Pics below.
PM me if you want any info on the mod but like I said, Mathias'
and Jools pages pretty much cover the basics.

good luck..

Steve
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  #3  
Old 05-03-2010, 08:26 AM
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mldee (Mike)
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Funny, I was planning on dumping my SP900NC's soon, as I never use them, but you both given me some incentive to reconsider. Just the challenge is reason enough and who knows, I might get interested in planetary imaging as Saturn becomes more photogenic.

I like the cooling mod Steve, would be interested in seeing your site if you can get it back up again
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Old 05-03-2010, 08:28 AM
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Exfso (Peter)
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If all you are doing is the long exposure mod, it is very easy, but does require a steady hand and some soldering skills. I have modded at least 40 of these for Matthew Lovel (Telescopes and Astronomy).
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Old 05-03-2010, 09:44 PM
alanfvic (Alan)
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Thanks for the advice and the pics Steve. I'm tempted to try the Amp-off mod now, but one step at a time.
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Old 10-03-2010, 11:14 PM
alanfvic (Alan)
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LX mod completed now with the 4066. I won't post any circuit for the pin/pad 10 enable via 4066 switch since I have seen it has already been posted elsewhere.

It's been cloudy here in Melbourne so I am just looking at dark frames without any lens.

I don't really understand why I am not seeing any amp glow. I will attach a dark frame taken with 120 sec exp at 70% gain. Noise is clear but no amp glow.

I can't expose even 1 sec at 100% gain before noise appears (unless I lower the brightness in which case I just get less noise but still no amp glow even at 120 sec). This doesn't seem to agree with results posted elsewhere of 120 sec exp at 100% gain showing amp glow. Have I missed something? Here are the settings from WcCtrl:

******** Capture Settings:Wednesday, 10 March 2010 / 11:56:20 PM ********
Program :WcCtrl - WebCam Control Utility (V 1.6.52)
Cam Driver : Philips SPC 900NC PC Camera (0x8818d46)
Comment added : a comment
******** Capture Cam Settings:10/03/2010 11:56:20 PM ********
Set-String : <64:32:0:0:0:16:255:0:0:1:136:42:0: 0:0:0:44:0:0:0:0:>
Brightness : 50% - raw: 64 (0 .. 127)
Contrast : 51% - raw: 32 (0 .. 63)
Saturation : 50% - raw: 0 (-100 .. 100)
Gamma : 52% - raw: 16 (0 .. 31)
Color Mode : 255(0=off)
WhiteBalanceM : 1(0=lamp,1=sun,2=FL,3=manual,4=auto )
WhiteBalRed : 53% - raw: 136 (0 .. 255)
WhiteBalBlue : 16% - raw: 42 (0 .. 255)
FPS : 0(0..5=5,10,15,20,25,30)
NonSC Exposure: 0(0..10=longest to shortest - depends on camera)
Gain : 70% - raw: 44 (0 .. 63)
FlipHorizontal: 0(0=off)
FlipVertical : 0(0=off)
AutoExposure : 0(0=off)
AutoAll : 0(0=off)

Alan
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Old 10-03-2010, 11:50 PM
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kinetic (Steve)
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Hmmm. not sure what's going on there Alan.
Have you verified it's a successful LX frame?
That looks a bit like a normal frame maybe?
There should be some hot pixels at 120secs.

Here is a 120 sec frame I just did using my
cooled 900 but with cooling off.
Mine is a non-amp-off mod.
Purely lens covered, 120 sec, no compression
Unstretched 1st pic, stretched 2nd, 3rd a screengrab of the settings.

Steve
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Old 11-03-2010, 12:18 AM
alanfvic (Alan)
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Hi Steve,

Thanks, looks like my LX mod is not working. I just tested with room light and still get a dark frame! It appears the shutter is not opening at all. Hence no amp glow. I'll have to look into it.

Alan.
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Old 14-03-2010, 08:47 PM
alanfvic (Alan)
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I have checked the circuit and everything seems ok. The shutter stuck closed seems to be a rare intermittent connection when certain wires are flexed, and hard to reproduce. I have verified it is normally stuck open when in LX mode, and working normally when the parallel port is disconnected.

The real problem seem to be that I can't get access to my parallel port (IBM T23 laptop/Windows XP). I have tried K3CCDTools (the free version), QCfocus, and wxAstroCapture, and for all of them, pin 2 of the parallel port stays fixed at 5V regardless of any long exposure capture attempted. So I just get a standard short exposure frame every time. I have tried a couple of independent printer control programs, tried enabling interupts on the port, but nothing so far allows me to bring pin 2 down to 0v.

I have tried manually holding the LX input to earth with shutter open, and disconnecting at just the right moment and I can get long exposure. That's at 1/5 sec frame rate - I can disconnect at the right moment occasionally using the countdown in QCfocus to judge when).

Alan
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Old 14-03-2010, 09:13 PM
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kinetic (Steve)
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Alan ,

is your BIOS for the PPort set to Bidirectional and 0378/0278?

Steve
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Old 16-03-2010, 07:29 PM
alanfvic (Alan)
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Hi Steve,

Thanks for that hint. I checked the BIOS and it was set to bi-directional, but I tried the other option (which is more the old PC standard) of ECP, and that has fixed the problem.

Finally I can see the hot pixels and amp glow. 100 sec dark frame with high gain shown.


Thanks, Alan.
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Old 17-03-2010, 04:32 PM
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kinetic (Steve)
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Quote:
Originally Posted by alanfvic View Post
Hi Steve,

Thanks for that hint. I checked the BIOS and it was set to bi-directional, but I tried the other option (which is more the old PC standard) of ECP, and that has fixed the problem.

Finally I can see the hot pixels and amp glow. 100 sec dark frame with high gain shown.


Thanks, Alan.

Oh good news Alan,
I knew it could possibly be the ECP/Bi directional PPort thing and
I just threw it in as a suggestion.
I have seen so many 'my mod doesn't work' threads on QCUIAG
that ended up being that, it's not funny

Glad it sorted, keep us posted how it goes.
Your post made me plug the poor old SPC SC2 back into the
focuser in what seems like years.
Maybe try cooling next, it sure does help drop the noise floor.
I'd try that even before the Amp-off mod because the amp glow
doesn't really affect exposures lower than 1 minute anyway even
with extreme stretching.

Steve
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