Need these 2 datsheets (SN755870 and RJH3077) . I'm trying to fix a busted Samsung 42" plasma with defective Y drive and Y buffer pcbs. While the SN755870 is made by TI , their website wont acknowledge it's existence (OEM).
On Sun, 2 Nov 2008 20:03:38 -0800 (PST), jango2 put finger to keyboard and composed:
Not a datasheet, but if you need one, it'll cost you $28.50, retail:
- Franc Zabkar
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On Sun, 2 Nov 2008 20:03:38 -0800 (PST), jango2 put finger to keyboard and composed:
If it helps, the RJH3077 could be made by Renesas. See page 10 of the following document.
Renesas Discrete Catalogue:
R = Renesas (Fixed) J = Power transistor (Fixed) H = IGBT + Diode
30 = voltage class, 300 - 309V 77 = serial number (???)- Franc Zabkar
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On Sun, 2 Nov 2008 20:03:38 -0800 (PST), jango2 put finger to keyboard and composed:
Renesas Discrete Catalogue:
Page 68 of abovementioned catalogue lists two IGBT transistors for "Plasma Display Panel (Build in Diode)".
RJH3077DPK - TO-3P, VCES = 330V, IC = 50A, IC (peak) = 200A, Vce(sat) = 1.6V , Tf = 0.16us, Trr = 0.1us
- Franc Zabkar
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On Sun, 2 Nov 2008 20:03:38 -0800 (PST), jango2 put finger to keyboard and composed:
See page 14 of this document:
... and maybe this one:
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
rs/rej02a0003_guide...
Hey thanks Franc, I suspected it might be an IGBT. This helps a lot. Hey franc i'm stuck with the same symptom on 2 monitors, one's a Samsung plasma, the other a sony LCD. Hard to explain the problem in words but i'll try. The picture is pretty normal except when i'm looking at a face, i get contours inset with a colour shade thats slightly off normal. I will upload pics by this eve. Would be great if you could help me. Thanks again, Jango :)
Hi Franc.
sorry to barge into your mailbox, but i couldnt upload pics to sci electronic repair.
Attached please find the pics of the plasma problem i was describing. The problem is more acute with a higher contrast setting.
The history so far:
I have 2 of these units for repair , lets call them unit R and unit S.
Unit R came in with no picture no screen. Just the blue power led would come on flash at .5 sec intervals and then nothing. I could turn on and turn off power but no picture or light. I opened her up and found a shorted diode on the Y drive pcb D5010. Thought the manual (as usual) has no schematic for the Y pcb , i did some tracing of the section and found it to be a rectifier at the output of a transormer based sub power supply driven by a 5M0380R (5 pin device) on the primary side. A 7815 and an optocoupler driven by a H431 (three terminal reg) lay in the feedback loops (4 windings on the transformer). The diode on replacement would heat up indicating a short ahead. I located this short in the Y buffer pcb which receives over a 100 volts from this diode. The y buffer pcb has 8 SN755870 panel drivers on it. My short circuit measured 47 ohms. I used a trick here, keep ohm meter connected, heat each of the 8 SN755870's with my smd hot air blower. i noticed the short 47 ohm reading diminishing slightly down to 38 ohms when i hovered over 1 particular ic out of the 8. I desoldered the suspect ic and voila, sure enough my short disappeared.
On powring up now, i'd see a picture with the symptom illustrated in the pics. I've tried swapping all the boards from the other set "S" to no avail, maybe cos the other set has the same problem. I'm lost here.
Unit S came in with a picture that was continuously varying in brightness. Sort of like white flashes. Couldnt really tell if this contour/rainbow effect was present then. I noticed that i could'nt vary VSCAN coming in from a DC to DC power supply board. The sticker on the chassis listed Vscan at -185 volts but i was measuring variations between -80 and -300 volts. The V scan preset wouldnt let me set voltage to the desired -185. Hooking up a scope to the vscan line showed that the voltage varied in sync with the white flashes. I opened the DC to DC convertor , poked around a bit and i found an open
180K ohm resistor in series with the preset. Repalced it and mt white flashes were solved :). This is when i noticed the contour/rainbow effect. In trying to move the powered set around 2 IGBT's RJH3077 blew along with a driver ic IR2106S. I'm now left with 1 working Y drive board. The other set "R" has 1 SN755870 missing but when i plug that in i get the same contour/rainbow effect, of course with a horizontal black band in the region of the missing buffer.I have the service manual and i can get into servce mode. The manual has no schematcs for Y section.
Any clues?
Your help will be really appreciated.
Jango
Woops, can't post pics here (how dumb of me). I guess i'll mail u direct , hope that's ok with u !
flickr links to the pics.
I forgot to mention that i notice a lot of snow, even with a vga input. The snow increases and turns into a lot of noise when varying 2 presets on the Y drive pcb caleed V_RR and V_FR. At some particular preset setting the centre of the screen goes red with a lot of noise at other settings it goes white and extremely noisy almost like a plain raster.
On Mon, 3 Nov 2008 22:45:55 -0800 (PST), jango2 put finger to keyboard and composed:
I have posted your photos on my web site. Perhaps someone else can help you.
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
document:
one:
Jango.. I have worked on some older video processors used in multimonitor video walls and I have seen what looks like the problem you are seeing in the faces.. What was causing my problem was the data on one of the higher number data lines D6 or D7 line was completely missing (8bit A/D processor). You might want to scope your data buses. Mine turned out to be a bad plated through hole. Just a thought. Hope it helps Dave Mc
Wow, thanks kvm, that lead is very encouraging . Gonna scope them busses first thing in the morn. Wondering if that means i should be hunting for breaks in the Y drive, or logic board or LVDS or input module......Whatever the case , i see faint glimmer of hope. And thanks Franc for the webspace. :) cheers !
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