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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Mon Jul 25, 2011 3:44 pm Post subject: |
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| dvh99 wrote: | | but for now they work just fine. |
congrats Dennis but what about the pic, What have you noticed there? Are any of the common HDM issues better than before like unstable scan with short retrace?
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Mon Jul 25, 2011 3:47 pm Post subject: |
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| macgyver655 wrote: | | draganm wrote: | Every time I read this thread lately I think "wow, imagine what could be done to the MArquee today if there was a serious effort to re-design some of the major parts like HDM, VIM, CLM, etc. I bet some of the boards would wind up with 30% fewer parts using newer technology and also getting rid of obsolete crap like the audio circuit on the VIM.
I know the economic side is a bust but it doesn't hurt to dream  |
The Marquee would end up almost as good as an Ampro ..... 
Of course as we see.... it takes an Ampro expert to try to resolve these Marquee quirks......  |
Never even seen an Ampro, I'll take your word for it.
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Mon Jul 25, 2011 4:03 pm Post subject: |
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| draganm wrote: | | dvh99 wrote: | | but for now they work just fine. |
congrats Dennis but what about the pic, What have you noticed there? Are any of the common HDM issues better than before like unstable scan with short retrace? |
hi dragan, i haven`t seen any differences but i never encountered unstable scan problems before either.
i did this to reduce switching losses due to the very low rds on and much lower Ciss of the cree fets and thus cooler running of the hdm.
i am still awaiting my mosfet drivers i ordered from ebay on 12-07, these will allow me to up the voltage a bit so the crees are driven at their optimum voltage.
http://cgi.ebay.com/UC3708-Power-MOSFET-driver-35V-3A-source-sink-x4-/170645550139?pt=LH_DefaultDomain_0&hash=item27bb44743b#ht_2566wt_954
the hdm heatsink still gets too hot to touch right now, i will update as soon as the drivers arrive.
with those drivers in i will reduce backporch and see how far i can reduce this without introducing ringing.
dennis
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Mon Jul 25, 2011 5:15 pm Post subject: |
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http://www.youtube.com/watch?v=RKPNFwHcyKA&NR=1
this is for the thread starter.
always liked the john williams version best until i heard and saw this, TODAY!
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Tue Jul 26, 2011 12:51 am Post subject: |
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The original HDM has three 600V mosfets connected in series for a blocking capability of 1800V. Two of the 1200V Cree parts could block 2400V which is an improvement over the original circuit. Three of these in series is not necessary. Dissipation could be lowered with two.
There are other parts on the HS contributing to the heat. The width regulator is a series pass type circuit kinda like a LM317. It regulates by dropping voltage across the resistance of Q9 and especially Q10.
Scott
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Thu Jul 28, 2011 7:22 pm Post subject: |
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for sale: 1 cree mosfet!
finally the heatsink remains cool enough to touch, with 2 fets.
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Fri Jul 29, 2011 7:15 pm Post subject: |
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| tse wrote: | | The original HDM has three 600V mosfets,Two of the 1200V Cree parts could block 2400V which is an improvement over the original circuit. Scott |
just like I said earlier, 30% fewer parts
I'm kind of glad I don't have your knowledge or I would add Legacy electronics re-engineering to my list of things I do obsessively.
| dvh99 wrote: | for sale: 1 cree mosfet!
finally the heatsink remains cool enough to touch, with 2 fets. |
it's not that simple is it, just plucked it out? You didn't have to bridge the through holes with a jumper wire?
more importantly, will you have a write-up on this mod with pics once the final version is done.  I would like to send a Cree'd board to my customer who's machine does this on short retrace after 1 hour (definitely heat related). I hate leaving things like this un-solved.
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Fri Jul 29, 2011 7:43 pm Post subject: |
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Curved lines at the top are usually one of two types. Curve the same direction usually indicates a "phase" problem from sync or horizontal oscillator issue. Anything that deals with the drive can do this.
Curves in different directions on the two sides is caused by the width regulation circuit not stable (or power supply problems).
Scott
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Nashou66
Joined: 12 Jan 2007
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Location: West Seneca NY
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Fri Jul 29, 2011 11:45 pm Post subject: |
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If the bottom mosfet is jumped out the caps in parallel with the mosfets will have to be changed to keep the same retrace time.
Scott
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dvh99
Joined: 25 Dec 2009
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Location: nederland
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| Posted: Sat Jul 30, 2011 11:24 am Post subject: |
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scott, i have taken out q3 and their parallel caps (c4 & c5, with their ferrite beads) and jumped them.
i have watched 2 full length movies with it without any problems, should i still install other value caps for best performance or reliability.
even the convergence was spot on (as always) after removing the fet.
dennis
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Sat Jul 30, 2011 6:04 pm Post subject: |
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You are lucky that nothing bad happened. The flyback cap value (parallel/ serial combination of C4, 5, 6, 7, 10, 11, and C8||C13) have a direct effect on the retrace time and flyback voltage. As the retrace time gets less the flyback voltage gets higher.
There are two windings in each horizontal section of the deflection yoke. Above 60kHz the windings are placed in parallel for an inductance of 180 - 200 uH. So the parallel inductance of the three deflection yokes is near 66uH. Below 60kHz the windings are connected in series for something like 800uH. I don't have a yoke handy to check so I am going from memory. The 800uH might be a bit different.
Above 60kHz, with long retrace, C8 and C13 are switched across the mosfet stack, below they are removed from the circuit.
Below 30kHz a relay switches across Q7 and C10 and C11.
There are alot of combinations creating different retrace times and flyback voltages.
Attaced are a couple of Mathcad pages showing original Marquee and your mod results with projector running at 68kHz.
Scott
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dvh99
Joined: 25 Dec 2009
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Location: nederland
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| Posted: Sat Jul 30, 2011 10:14 pm Post subject: |
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are those differences dangerous for my projector?
the pj is always set on short retrace btw
scott, in the 1st schematic you have 1,5us for retrace and in the 2nd 1,72us, where did you get that different number?
i will put the caps back btw.
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Sat Jul 30, 2011 11:24 pm Post subject: |
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No, you are safe. With your mod the flyback voltage is about 1516V and the retrace time is about 1.72us. With the two 1200V parts in series you have plenty of headroom.
The original configuration has about 1744V flyback voltage with 1.5us retrace. That is pushing it alot closer to the limit.
Scott
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dvh99
Joined: 25 Dec 2009
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Location: nederland
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| Posted: Sun Jul 31, 2011 3:39 pm Post subject: |
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dragan here are the pics.
24volt is taken from the last pin on connector J11 from the daughterboard.
this "mod" is completely safe, 5 hrs and the hdm gets warm but not hot anymore.
when i receive the uc3708n drivers the lm317 can be omitted.
update about this will follow.
dennis
forgot 2:
i used the sbyv27-200v as i had them lying around, 1n4002 will be fine too i guess.
between pin 1 and 2 there is a 260ohm resistor in case the pic wasn`t clear, the other one is a 3900(3k9)ohm resistor.
both 1206 case size smd 1/4w.
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Mon Aug 01, 2011 4:22 pm Post subject: |
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thanks Dennis, looks rather challenging. There's many places to make a mistake for someone doing it the first time. However the results are impressive, both from all the numbers Scott crunched as well as the temp. drop in the HDM. I will have to try this when I get a chance.
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Mon Aug 01, 2011 6:21 pm Post subject: |
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if you have all parts at hand this is a 1 hour thing.
it`s worth it.
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dvh99
Joined: 25 Dec 2009
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Location: nederland
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| Posted: Mon Aug 01, 2011 7:25 pm Post subject: |
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mhhh it looks more 3dish too with those new fets or is that just my imagination  .
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Mon Aug 01, 2011 7:35 pm Post subject: |
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recently saw the newest jvc 3d thingy...
compared to my marquee it is a toy, the comparison is not even funny but a complete disgrace for the jvc.
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Tue Aug 02, 2011 6:38 pm Post subject: |
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the uc3708n drivers do not seem to work.
first i changed out u1 and tried and the pj wouldn`t turn on then i changed out the other mc34151 with the uc3708n and now i get a clicking sound of the relay on the hdm and a flicker on the clm with the lvps lit.
3rd from right i guess.
tried with the 20v and straight 24 volts.
any ideas?
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