Dynex DX-LCD37 Bad Caps!

[redtux777]

Hi, I have a Dynex DX-LCD37 with bad cap(s).

The tv turns on and off by itself.
The orange light blinks 15 times when it does.
I have found 1 cap that looks bad. 450v 100uf

My question is should I just change out the one that looks bad, or all three on the board of the same size.

There are a lot of caps to choose from here. What one should I get?

http://www.newark.com/webapp/wcs/sto...&storeId=10194

Should I look for anything ease?

Here are my pics- THANKS!

[aaronwt6]

Re: Dynex DX-LCD37 Bad Caps!

I would change all 3. If one is bad, the others are probably not far behind.

[redtux777]

Re: Dynex DX-LCD37 Bad Caps!

I would change all 3. If one is bad, the others are probably not far behind.

Thanks I will do that.
I also found this thread of what kinds of capacitors to get.

https://www.badcaps.net/forum/showthread.php?t=414

[redtux777]

Re: Dynex DX-LCD37 Bad Caps!

Still blinks 15 times and shuts off by it self randomly then turns back on after replacing caps. any help?

[Andrew F. Ali]

Re: Dynex DX-LCD37 Bad Caps!

Check the capacitance and ESR of the other caps. Especially those around the connectors on the board *(at the top of the second pic)

[kg4ezq]

Re: Dynex DX-LCD37 Bad Caps!

Hello, this is my first post.

I am a reasonably experienced tech, but not with TVs, and have the same problem as described in this thread. I have already spent a fair bit of time troubleshooting and have determined the following:

• The power supply is producing the correct voltages (5V standby, 12v and 24v when on)
• I have checked the ESR of all of the electrolytic caps on the power supply and all of them seem reasonable (according to the classic Bob Parker chart)...they are all elite brand caps, ED series on the LV side and PD series on the HV side...FWIW I checked them with an LCR meter at 1kHz
• The problem occurs whether or not the TV has been on recently (i.e. is warm)
• I have used freeze spray on all the boards to try to isolate a thermal issue with no results
• I have viewed the output of the 5V supply on the scope and it appears very clean
• The output of the 12v supply also appears clean, with some minor, <60mVp spikes
• The 24v output is not especially clean, and looks awful when I have the inverter board connected, but I'm assuming this is due to HV transients from the inverter...?
• A careful visual inspection of both sides of all boards reveals nothing unusual
• when the TV operates it operates normally, except that sometimes (not always) there is a constant flashing orange light instead of the usual steady green; this suggests to me that whatever the fault is it is something the mainboard can detect
• The fault occurs whether or not the T-CON board is connected, although I thought I heard some high frequency screeching from the T-CON's local DC-DC converter just before cutoff a couple of times...perhaps a symptom of a voltage drop? (But I couldn't measure one)
• I cannot observe a voltage drop on any supply just before the TV cuts off, there is a minor (100mV) voltage rise just after cutoff, but I'm attributing that to the switchmode power supply
• I have very little experience with TVs and am close to giving up on this one

Thanks a million in advance to the mystical guru who I'm certain is about to appear and clear all this up

[kg4ezq]

Re: Dynex DX-LCD37 Bad Caps!

Possible success!

I haven't actually fixed it yet, but when I used my DC load to test the 24v supply it dropped out of regulation after a few minutes at 2 A...I'm assuming 2A is appropriate. I also heard the classic high frequency screech just before it dropped out.

I'm going to re-cap the low voltage side of the power supply completely and see how that goes. Again, I tested each of the capacitors already, but the two big 2200uF caps on the 24v supply got missed the first time, I tested them after my experiment with the DC load and their ESR is definitely a bit on the high side. My ESR meter can't do 100kHz, so I can't be 100% sure (i.e. compare to cap mfr data sheet), and there is no 2200uF row on the Bob Parker chart, but if I extrapolate, the ESR is about twice what it should be.

Additionally, under magnification several of the caps to appear slightly bulged, especially compared to their neighbors.

I will post back in a couple of days with an update after the caps arrive. If it works I will include Mouser part #s.

Fingers crossed...

[kg4ezq]

Re: Dynex DX-LCD37 Bad Caps!

FWIW the Nichion HD series seems to be the ideal replacement for the Elite ED series. The dimensions are pretty much the same for all values and the ESR and ripple current is considerably better in the Nichion HD than the Elite ED for every value I looked at.

I will stop talking to myself now...

[mmartell]

Re: Dynex DX-LCD37 Bad Caps!

No no no, please, go on.

Let us know how it turns out.

[kg4ezq]

Re: Dynex DX-LCD37 Bad Caps!

There are people here!

Hopefully I'll have the caps in by Friday or Monday and will be able to post an update. I may try to post the part list sooner, as it was a fair bit of homework selecting the right ones, and it may be useful to someone else even if it doesn't solve my issue. The 715T2512-2 power supply seems to be used in a lot of TVs from this era, so I probably won't be the only one looking to re-cap one.

[kg4ezq]

Re: Dynex DX-LCD37 Bad Caps!

Right, replacing the caps...I still don't have them yet but wanted to post my homework as far as ordering them in the hope that it saves someone else the trouble.

I used the Nichicon HD series where I could, the only two exceptions are for the (2) 2200uF 35v (C981,C982) because the HD series doesn't include a 2200uF and the (1) 470uF 16v, which was out of stock in the HD series at the time of my order. I substituted the Panasonic FR and FM series, respectively.

Actually, the Panasonic FR and FM series (which are very similar) are a closer match to the Elite HD series, they have a nearly identical ESR rating, but I went with the Nichicon HD because a) I prefer Nichicon and b) the HD series has even better ESR specs.

So, here's the parts list for replacing the caps for the low voltage side of the 714T2512-2:

(These go from right to left if you have the board oriented right-side-up with the AC input connector at the back left corner)

C981,C982 (2200uF 35V): Mouser P/N 667-EEU-FR1V222
C983 (1000uF 35V): Mouser P/N 647-UHD1V102MHD
C922 (470uF 35V): Mouser P/N 647-UHD1V471MPD
C954,C947 (470uF 25V): Mouser P/N 647-UHD1E471MPD6
C952 (470uF 16V): Mouser P/N 667-EEU-FM1C471L
C946 (1000uF 25V): Mouser P/N 647-UHD1E102MHD
C950,C951 (1000uF 16V): Mouser P/N 647-UHD1C102MPD1TD

And here's a link to a shopping cart with all these already in it :

http://www.mouser.com/ProjectManager...sID=2a34dd09c2

[kg4ezq]

Re: Dynex DX-LCD37 Bad Caps!

It was the power button!

Something had gone wrong mechanically with the tact-switch for the power button and it was just constantly flapping on and off. I disconnected it (for now) and the TV is back to normal!

Turns out those 2200uF caps probably weren't bad... I was in a hurry when I tested them because I had to leave and I don't think I calibrated my LCR meter before I took the reading, so the "high" ESR I measured was probably just a normal ESR + the test leads. That's probably the same reason I didn't see a high ESR the first time I checked the caps...boo me.

In the end, since the TV is 7 years old now I'm still glad I re-capped the low voltage side of the power supply. It cost very little money and probably extended the TV's life a good bit.

In all my years in electronics, I don't think an intermittent issue has ever been the power button...

[Tedybear]

Re: Dynex DX-LCD37 Bad Caps!

After repairing arcade games for the last 20 years? You'd be amazed at how badly the simple stuff will trip us up.

The cap with the snot hanging out of it? Yeah..that's an issue waiting to happen. So all you did was good to extend the lifespan of the set.

You figured it out! Congrats. And just because I can be immature at times?



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