Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
I get a brief voltage between DM802 and RM806 but that drops to zero. I still get around 8v on the other side of DM802. I can no longer get stb to come on even after letting the TV sit unplugged. I replaced CM804 and CM808 even though they didn't seem bad.
gnuorder
Member
Last Activity: 01-29-2018, 10:47 AM
Joined: 02-10-2016
Location: Tampa
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
It fluctuates between roughly 13v and 10v. Also, I don't get 5vstb at all any more....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
Never mind, they are common....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
Sorry it's been a while before I could get back to this. I measured today to remind myself. At first I have stb but it goes to 0 after I turn on the TV. It use to be slow but now much quicker. When I first plug the TV in, I get 5.15 at stb and it seems stable. Once it shuts off, I can't get stb to come back unless I unplug it a while. First plugged in today, I got 5.15v at stb, .22v at the emitter of QB801, 17.2v at the collector and 0 at the base. When I power on I got 15.35v at the base, 9.1v and dropping at...Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
Yes, that is true. When I started working on it today I was getting close to 15v off the emitter, now I'm getting 0.23V. I can let it sit for a while and start again. It will have to be tomorrow though....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
Apparently not. I measure 0v at the connector between pins 3 and 4....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
The voltage across CM804 was 8.89 but was slowly dropping, 8.50 last check. The voltage across RM806 was 0v....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
So if the collector is going to 0v, the opto is switching off. I should measure the voltage between rb814 and rb815 to verify that it's shutting off.Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
I did assume the middle connector of the transistor was the base so those may be reversed. Looking at the photo pjs2015, they are reversed and I found the opto. Solder connections look good for all but the opto which I haven't checked yet....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
I get 0v at the collector and 8.9v at the base. Before it cuts out I get 15.26 at the collector and 17.35 at the base....Leave a comment:
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Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
I'm getting back to this TV. I'm getting 14.5v at the QB801 emitter when it's working and 0.22v when it's not.
I'm still confused about the two zeners in series. I only see one zener ZB802 and one diode array DB802. I ordered replacements for both. We'll see how it goes. Did you have any luck?Leave a comment:
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Re: Viewsonic NX2232w with no video or audio
I got a used main board on ebay that is suppose to be good. It still does not come on but with some differences. if the boards are cold, it doesn't power on at all. standby orange LED goes out. If I warm the boards up with a hair dryer it will power on but still no picture and menu, source, etc buttons don't work. With this board I can power it on and off. my old board I couldn't power off after I powered it on. Also pin 7 on the power connector is labeled ADJPWMA in the schematic and measures 3.27 and pin 8 is bclon like I suspected...Leave a comment:
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Samsung ln40b640r3f shutting off and wont power on
I have the same power board and the same problem as this thread:
[url]https://www.badcaps.net/forum/showthread.php?t=51557&highlight=bn44-00264a[/url]
Same symptoms. If I leave it unplugged for a while I can get it to work fine again. Then after a while, it cuts out. I'm up to checking the zerners. Measuring QB801 at LB812 I get 14.5v with the backlights on. I'll check what I get when it cuts out.
OK, it cut out after about 10 minutes and reads 0.23v. Disconnected and reconnected power and it went from 0 back to 0.22v.I have the same power board and theLast edited by gnuorder; 02-17-2016, 09:45 PM. -
Re: Samsung LN40B640R3F -- standby voltage slowly drops/drains to zero
I don't see the two zeners in series. I just see zb801. Do you mean the switching diode db802 as well? I've got the same problem.Leave a comment:
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Re: Viewsonic NX2232w with no video or audio
Found two more 1117 regulators, I104 and I105. Voltage at the pins are 0,2.44,5 and 0,3.2,5. Forgot to mention yesterday I measured power from the power board on standby and on. Pins 1-9 on are o,5,0,0,5,5,3.2,0.1,25.3 and standby 0,5,0,0,5,5,3.2,2.3,26.3. Pin 8 is the back light on line.Last edited by gnuorder; 02-13-2016, 08:42 PM.Leave a comment:
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Re: Viewsonic NX2232w with no video or audio
Hmm, what happened to the edit button?
Anyway, I tested I202 and it acts like a 1.75v regulator. pin 1-3 voltages are 0, 1.78, 5. There are three 7585-3.3 regulators that all measure 3.28v. Then there is one I can't find. It's I304 and the numbers on it are 1084 0729AL and the pins 1-3 voltages are 0, 1.24, 3.05.
ID' I304 as an AIC1084 1.5, 1.8, 2.5 or 3.3v regulator with a 5v input. I'm beginning to suspect there is a problem there.
Also found the edit button on this post but not my...Last edited by gnuorder; 02-12-2016, 05:26 PM.Leave a comment:
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Re: Viewsonic NX2232w with no video or audio
The caps all look good though that doesn't mean they are. Trying to identify the regulators and measure then. Do you happen to know what's under the heatsink at I202? I assume its a regulator based on the need for the heatsink.Leave a comment:
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Viewsonic NX2232w with no video or audio
I have a Viewsonic NX2232w that seems to power up fine but I never get video or audio through the tuner or VGA. When I plug it in, I get an orange light on the power button. When I turn it on, I get the blue light, the three birds appear then the screen goes blank. After that, none of the switches respond, or if they do I can't see, and I can't power it down. After testing it. I notice the heatsink on IC301 is cold. Don't know the part number because of the heatsink but the main board is part number 6201-70220000001.
It seems the main board is working because it shows up on my laptop...Last edited by gnuorder; 02-11-2016, 09:13 PM. -
Re: New Members - please post your introductions here
my name is Greg and I'm looking forward to fixing some of the electronics around the house as well as friends electronics. I use to do board level repairs on mainframes and CRTs using standard parts but looking up these new parts are a whole new world. I'm hoping to learn a lot.Leave a comment:
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