CurtPalme.com Home Theater Forum

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

ok, spent some time talking to my friend at work about this, admittedly he has not studied the circuit but there are some issues he brought up I thought worthwhile discussing. I mentioned to him that I thought maybe one of my drivers had failed and the fact that Dennis's were still working, only difference is Dennis used a 40V rated driver vs. 35. He said that even though you might be giving a 35V driver only 24 volts there is a possibility of a backwave or reflection from the MOSFET that is much higher. These transients shows up as spikes and are hard to see even on a scope.
So I said wouldn't there have to be a Diode in the cicruit somewhere to protect the driver? Then it occurred ot me that there was, the GTO was acting as a clamp for both the Drive and the gate voltage right? Scott pointed out back in July

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

second problem, the HDM shorts out Q3 under 30KHz which isn't a problem since we're removing Q3 anyway. however it also shorts out C10 and C11.
So with this modification at low scan rates c10 and C11 are shorted but now we're also missing C4 and C5 in the core. Now we're down to a pair of 1KV rated caps in a 1600 volt peak to peak circuit. Is that even safe?

Nashou66 · Posted: Wed Jan 25, 2012 5:02 am Post subject:

Drags, when you turn it on is a source connected or is there no source? And when it worked before the cap change was a source connected?

I'm wondering if this mod only works for the higher frequencies?

Just talking out my arse too Wink

Nashou

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

there is an isolation transformer between the fet and the driver.
the fets work just fine at lower frequencies, though i haven`t tried anything below 1280*720*60hz.

you got the 24v at p17 right at the pins, why not at the daughterboard like i did?

did you get the24v after r154 or before (thus straight from the lvps), the 22ohm fusible (check that resistor first, it might be blown)?

the caps don`t see the full voltage swing but half of it but it`s still close to their max allowed voltage, the 2n2 i put in has a 2kv rating and has the same lead spacing as the holes on the pcb.

it`s a good idea to use 2kv rated i guess.

why did you get 6r8 fusibles btw?

edit: these are much cheaper and 1% and 50ppm.

http://www.farnell.com/datasheets/483924.pdf

http://www2.mouser.com/ProductDetail/Cree-Inc/CMF10120D/?qs=D3QG1iK7FqhcMqyHiZ68bA%3d%3d

prices of the fets have dropped substantially.

22usd a piece.

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

Nashou66 · Posted: Wed Jan 25, 2012 6:50 pm Post subject:

Cree was mentioned on CNBC as a great stock to buy, its been up since you started this project Drags! They maybe reading your posts here Wink

Nashou!!!

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

my daughterboard isn`t captured either, the 24 volt trace goes to a resistor and that`s where i get the 24v.

i have over 100 hours on the projector since i installed the fets so no worries of overstressing a trace Smile

.

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

so it looks as I suspected, bad driver. U1 is shorted between pins 4 and 5, measuring basically no resistance

pin 4 - channel B Logic input
pin 5 - Channel B Output - Sources or sinks current to turn-on or turn-off a discrete MOSFET or IGBT

http://www.clare.com/home/pdfs.nsf/www/IXD_604.pdf/$file/IXD_604.pdf

So I'm having a hard time believing that pin 17 as a direct source from LVPS could have caused this. I see there's a small decoupling cap for noise and R154 fusible which is safer for the circuit in case of a serious failure or short but to actually damage the driver by grabbing the supply before that point? Either the driver Dennis used is a lot more robust or I just got a defective one? I'm leaning towards the latter as the weird raster anomaly I had right at the start might have been crosstalk or the internal voltage leakage from the driver right off the bat.

I'm going to order the better UC3709 driver , some 2KV rated Poly's in 2n2 and 3n8, and move the yellow wire to after the R154 fusible resistor. Anything else? Confused

Nashou66 · Posted: Sat Jan 28, 2012 4:19 am Post subject:

Drags come off the other side of the r22 so you have that extra safety of the fuse.

Athanasios

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

make sure the lead spacing of the caps is the same as on the hdm pcb and get polypropylene caps.
wima evox rifa epcos vishay, all are fine.

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

Nashou66 · Posted: Sat Jan 28, 2012 6:16 am Post subject:

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

just want to be sure this is the right driver

http://www.mouser.com/Search/ProductDetail.aspx?R=UC3709Nvirtualkey59500000virtualkey595-UC3709N

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

da.

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

I've ordered the new parts but I'm still bothered by why the driver or drivers failed?In looking closer at the application sheets The Clare part can handle up to 4amps of peak current while the Texas Instruments 3709n is 1.5A max, about a third. So if there was any kickback from the Cree FET the Clare part should have been better suited.
I'm thinking it has to be a supply side issue, but there again both parts can handle voltage swings of 4.5 to 40 volts. The DC supply from the LVPS is regulated so that's practically impossible.
Last possible issue some kind of AC component to the power, I pulled 24VDC basically right off the Mobo where as Dennis grabbed it after the first de-coupling cap and 22ohm fusible resistor. Also, the first 2 de-coupling caps at U1 on the older board has a small MLCC of 500pf and 10uf /50V aluminum can vs. 2.2Uf Mylar + 47uf Alum. can on the newer boards.
Is it possible an AC component on the 24vdc line damaged the Clare drivers?

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

did you try the new drivers dragan?

http://www.infineon.com/dgdl/IPD65R660CFD2.5_.pdf?folderId=db3a3043163797a6011637d4e912003c&fileId=db3a30432e0bea21012e14dccc656df9

to take this all a little further i`m going to replace the mtp5n40 switching mosfet too.

this new device has lower input and output capacitance as well as a lower rds on, and should be a direct replacement

i`m hoping this will get the h-linearity better at the higher sweeping frequencies.

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

dvh99 · Joined: 25 Dec 2009 Posts: 1956 Location: nederland

you could start by measuring the voltage at the gate of the fets and work from there.

there should also be some test points on the hdm which could tell you more if you have the docs.

these new fets put less stress on the circuitry.

good luck hunting.

i took my entire projector apart yesterday because of some inexplainable errors i got (top and bottom bow messed up, black horizontal stripes in the picture, this affected the internal menu`s)so i cleaned the top motherboard and its connectors for the hdm and fgm and soldered the connectors for the video module and clm on the backplane and gave it a good cleaning (again by just pouring alcohol in the holes and inserting cards in the connectors).
now all is well again so if you have some errors you can`t explain and which happen randomly take a look at the backplane.

Nashou66 · Posted: Tue Apr 03, 2012 3:44 am Post subject:

Hey guys, Panasonic came out with a new ultra low ESR long life cap, the FR series.

http://www.panasonic.com/industrial/includes/pdf/EEU-FR_introductionsheet_2010-10-05.pdf

http://industrial.panasonic.com/www-data/pdf/ABA0000/ABA0000CE132.pdf

I think I'll be using these in some other Projects since I have all the caps for my marquee's in stock(FC FM series)

Athanasios