HANNS G HZ281 White Screen

[rrflorida]

Oh, that's a nice spreadsheet - thanks for the pointer. It indicates the tcon board is bad, but to check the panel first before replacing the tcon board. I'll search around the forum for how to do that.

[rrflorida]

Well, I'm not sure how to test the panel itself - I jiggled all the ribbon cables to the driver boards with no effect. Looks like there is no availability for this tcon board, so I'll need to attempt to diagnose and repair the one I have. The u102 transistor (circled in red) measures 7.3k Ohms middle to right leg, and 100 Ohms middle to left leg.

[momaka]

Originally Posted by rrflorida

The u102 transistor (circled in red) measures 7.3k Ohms middle to right leg, and 100 Ohms middle to left leg.

Good find.
But left leg is the input, so 100 Ohms is not necessarily a problem.
That said, see what voltage is coming to the left leg of U102 (with respect to ground) and what voltage it is outputting on its right leg (again, with respect to ground).

Also, could you please tell us what part number is written on U102?

[budm]

That is Voltage regulator IC, not transistor. See what Voltage you have on Vin and Vout pin.
I suspect the GAMMA Voltages are generated by U300, 301, get the P/N on both of them.
BTW, designator for Transistor is 'Q??', IC is U??







.

[rrflorida]

momaka and budm - thanks for the responses, really appreciate the help! I will gather the requested info Monday. Sorry for the delayed reply, was out of town.

randy

[rrflorida]

U102 is a 960T45. Left leg is 4.96V, right leg is 3.24V
U300 and U301 are both BUF 07704, which Mouser says is a LCD Gamma Buffer.

[budm]

Originally Posted by rrflorida

U102 is a 960T45. Left leg is 4.96V, right leg is 3.24V
U300 and U301 are both BUF 07704, which Mouser says is a LCD Gamma Buffer.

960T45 is 3.3V regulator, it is OK. http://www.gmt.com.tw/product/datasheet/EDS-960.pdf
GAMMA chips may be bad, need to look up spec sheet.

[rrflorida]

Data sheet for BUF 07704 attached

[budm]

So now you have the spec sheet of the IC showing what each pin is for, start checking the Voltages and report the reading for each pin, that will be a starting point.

[rrflorida]

Below and attached (the formatting is messed up here in the post) are the voltage readings from the BUF07704 chips. The OUT side seems to correlate pretty well with the IN side.



Pin U301 U302 Name
1 13.13 0 VDD
2 12.46 6.55 OUT1
3 10 5.31 OUT2
4 9.29 4.34 OUT3
5 8.9 3.78 OUT4
6 8.11 3.07 OUT5
7 6.76 0.64 OUT6
8 0.12 0 NC
9 5.47 7.21 OUTCOM
10 0 0 GND
11 0 0 GND
12 5.45 0.63 INCOM
13 0.76 0.65 NC
14 6.75 0.64 IN6
15 8.11 3.07 IN5
16 8.89 3.78 IN4
17 9.29 4.34 IN3
18 9.99 5.31 IN2
19 12.45 6.56 IN1
20 13.13 13.14 VDD

[budm]

https://www.badcaps.net/forum/attach...3&d=1536778904
Look at INCOM and OUTCOM of U302: U301 INCOM is 5.45V, OUTCOM is 5.47CV, but U302 INCOM is 0.63V and the OUTCOM is 7.21V
Look at pin 1 of U301 and 302: 0V on U302?

[rrflorida]

Oh, I messed up pin 1 on U302 (VDD) - it's actually 13.13V, so ok there.

I see what you are saying on INCOM/OUTCOM on U302. I just double checked:
12 INCOM: .64 steady
9 OUTCOM: climbs from 1-3 volts up to 6-7 volts everytime I probe it (climbs for about 30 seconds)

Are you suspecting U302?

[NOTE: I somehow started using the wrong U numbers, but will stick with the current U301/U302 for consistency]

[budm]

Yes, I expect U302 to behave the same as U301, it is buffer after all.

[rrflorida]

Ok, I will attempt to replace the chip and report back. Thanks.

[rrflorida]

fyi - having trouble finding the part - Mouser just cancelled the order and said it is discontinued. More later..

[momaka]

Maybe check with eBay. Sure there's a chance the part you get may not be genuine or high quality, but it could work fine. I've bought PWM controllers for motherboards before, and they worked okay. It's really only the high-power devices (MOSFETs, BJTs, and those STK stereo modules) that you want to either stay away from or use with lots of caution.
That, and the slow wait for the part to arrive from the far factories and shops of East Asia.

[Capt. Cap]

Doesn't look like any reliable retailers have it available in small order quantities https://octopart.com/search?q=buf07704&start=0

but you can get a single BUF07704 chip here
Probably not the real thing, but like momaka says, it may work well enough.

Let us know how it goes, I could be in the market for one myself soon

[rrflorida]

I ended up using eBay seller dicikey-max. We'll know more in 12-50 days.... Thanks for the suggestions

https://www.ebay.ie/itm/332274532555...m=332274532555