Atec av-420w 42" lcd tv

[tom66]

Another eBay find... picking it up tomorrow. (£40.00)

Fault is no power, might be stuck in standby (seller is unclear.) It's a 720p set. Another Swindon TV I need to collect, but will have a 32" Grundig (probably Vestel) to pick up on the same journey from Thatcham.

I've discovered that there are quite a few LCD/Plasma TVs on low buy it now prices on eBay. So search only for buy-it-now auctions, you can sometimes find a good bargain.

Might be a Vestel using 17PW16 PSU, which is a bit more expensive...

[vinceroger69]

Re: Atec av-420w 42" lcd tv

i seem to find a few cheap sets on my local gumtree sites there was 2 in my area yesterday a 36in sanyo stuck in standby and a 32 lg stuck in standby both £30.00 each just didnt have the cash for them as i am saving for a esr meter of rusmike at the minute as he has given me a very good price shipped for one. Hope these 2 for you tom66are a nice easy fix and for a newbie like me at reparing these i like the way you go into detail on your fault finding and your findings.

[caspermccormack]

Re: Atec av-420w 42" lcd tv

i seem to find a few cheap sets on my local gumtree sites there was 2 in my area yesterday a 36in sanyo stuck in standby and a 32 lg stuck in standby both £30.00 each just didnt have the cash for them as i am saving for a esr meter of rusmike at the minute as he has given me a very good price shipped for one. Hope these 2 for you tom66are a nice easy fix and for a newbie like me at reparing these i like the way you go into detail on your fault finding and your findings.

Yeah, gumtree is handy, here in Ireland we have Adverts.ie, but seems that a lot of people are on the look out for a cheap eay fix set, not always the case, and agree with your point about Tom, very helpful fella and full of info.

[tom66]

Re: Atec av-420w 42" lcd tv

Aww, thanks guys...

I'm picking the set up today. Turned out the guy who had the Grundig was going past dad's place so he dropped it off there.

[tom66]

Re: Atec av-420w 42" lcd tv

Okay... got it in the shed .

(A bit cramped with the 50" too!)

First thing I noticed is it's made in Germany! How interesting, never seen that before on a TV... Also, it's not a Vestel. Hooray!



The fault is: No power at all. No standby. Completely dead.

Let's play spot the fault...



Can you see it yet?



Hmm, this fuse looks like it has had a bad day. Indeed, the first thing I checked was the main fuse, and it was open, so I replaced it. Upon powering it up, the new fuse exploded, sending glass flying in all directions, and tripping the main garage breaker (32A type B) .

I suppose this is why you don't tend to see glass fuses in most electronics... they are dangerous! The original ceramic fuse did not rupture and appears to have failed safely.

Trace the short... well, the bridge rectifier is the first suspect in the chain. There is a short between the AC ~ terminals, but no short between + and -. Therefore, I suspect the bridge to have failed.



I will remove it to verify.

[vinceroger69]

Re: Atec av-420w 42" lcd tv

fingers crossed its a easy and cheap fix bet you have a recifier laying about somewhere to replace it.

[tom66]

Re: Atec av-420w 42" lcd tv

fingers crossed its a easy and cheap fix bet you have a recifier laying about somewhere to replace it.

I have a 4A one I can use for a 5 minute test, but not one designed for a heatsink. The 4A one will overheat otherwise.

I think I spotted part of the problem, the thermal paste for the rectifier is just completely dried up, and has probably lost some of its magic.

Just finished pulling it... nope, not shorted. However, there is another bridge rectifier on the board for the standby, so I guess that one is shorted. I'll probably replace the non failed one anyway because they are pretty cheap.

[tom66]

Re: Atec av-420w 42" lcd tv

Yep, it turns out the standby one has failed, shorted on each pin to every other pin. The other (main) one is okay. I'll dig out my bridges and test .

[vinceroger69]

Re: Atec av-420w 42" lcd tv

fingers crossed.

[tom66]

Re: Atec av-420w 42" lcd tv

Sadly, I broke the lead off the test bridge I had, so I couldn't use it... will have to wait for the Farnell order...

[tom66]

Re: Atec av-420w 42" lcd tv

Parts arrived today. Unfortunately, it's going to be a more expensive repair than I first thought.

I fixed the bridges and replaced the fuse. I powered it up, and "bang" went the 22uF 400V cap, and the NTC! Looks like the cap must have taken a shot of AC at some point and was internally shorted or walking wounded. It is completely burnt on one terminal and has made a nice mark on the PCB.

However, it also looks like the ICE2B0565 standby SMPS controller has been damaged. Once I removed the cap I still had a suspiciously low resistance across the +/- terminals. I powered it up on my 0-35V supply (current limit set to around 0.5A) with the voltage applied across live and neutral, and sure enough, the ICE chip (a DIP) smoked a bit. So, I need a new one of those. Luckily, it looks like almost everything else is okay!

I am building a variac inrush limiter, so next time I'll ramp up the board on the variac and see what smokes before ordering.

[vinceroger69]

Re: Atec av-420w 42" lcd tv

hope the new parts survied its a pity it needs more bits but hopefully once these are fitted it will be ok. NTC does that mean thermistor?

[tom66]

Re: Atec av-420w 42" lcd tv

Yeah, the new parts survived, but I've got multiple as it cost less than 50p for both.

Looks like the only source for the ICE chip is eBay.

Also the Pioneer is on hold - looks like I got a non isolated package so I need a mica spacer for TO-247 packages.

NTC is inrush limiter. Yeah it's a thermistor. As it heats up its resistance falls. So initially it limits current well then appears to drop out of circuit.

[vinceroger69]

Re: Atec av-420w 42" lcd tv

yes i saw the chip on ebay after you posted the part number bit expensive the uk supplier chinas cheap but items seem to take forever to arrive.

[tom66]

Re: Atec av-420w 42" lcd tv

So, I got the chip and caps today, and the TV now has working +5V standby and a steady lit standby LED. I used the variac to slowly crank up the power to check for magic smoke - nothing leaked out and I was happy to see the standby LED come on.

However upon powering up, well, it didn't. The main +5V measured 3V and the +12V measured 18V(!!) The +24V for inverter was fine (24.6V) and the +33V tuner supply was also good at around 32.5V. No sign of backlight or picture and power LED stuck in the standby condition (orange). PSON is good at 2V (changes from 0.017V when button pressed.)

Only upon looking closely did I notice a few "missing" caps. It looks like someone has professionally desoldered these (done a decent job), but never put them back or installed replacements. It looked so good I assumed that they were never installed as factory originals, but looking closely I can see the holes are not fully cleared and there are a few scratches from a soldering iron on the coppermask. I'm guessing a TV tech made a stab at replacing some caps - had they checked the fuse as a first thing, I suppose they would have found the main problem. These caps may have been bulging - but I've seen quite a few TVs with bulging caps that still work fine (obviously though they don't have long left to go before they completely die.)

As I don't have the caps in question I've made a best guess estimate using Panasonic caps. For the 5V before the inductor I used 1500u 6.3V FM; 5V after inductor got 1000u 6.3V FM; 12V after inductor got 680u 35V FR (only one I had lying around with a high enough voltage rating) and the 12V before inductor was still there. Other caps are Samxon, so-so quality. These rails probably don't handle much current, so large caps aren't necessary - the 24V (at 8A) uses 2x2200u 35V caps.

It's a flyback supply for the main output (and bizarrely, the 24V too), so the capacitance isn't super critical. Let's see if it works... be back shortly to report.

[tom66]

Re: Atec av-420w 42" lcd tv

Well, I'm pleased to report that it now works perfectly.

(Difficult to take a pic as it's right against the wall. Picture is absolutely fine; screen looks really good, barely even a mark of dirt on it!)

Sound works fine, looks like the amp chip has survived the 18V.

[vinceroger69]

Re: Atec av-420w 42" lcd tv

cool its nice when a repair goes to plan atleast its another set saved from the landfill were the parts a resonable price in the end? its still a very good set by looks of the picture have you picked any more up to repair recently?

[tom66]

Re: Atec av-420w 42" lcd tv

cool its nice when a repair goes to plan atleast its another set saved from the landfill were the parts a resonable price in the end? its still a very good set by looks of the picture have you picked any more up to repair recently?

8 quid for the parts in total. TV was 40.

No more at the moment.

[tom66]

Re: Atec av-420w 42" lcd tv

Finding a remote for this set is proving tricky as it looks like this is actually a custom Atec chassis - strange! But I may have found a compatible one. Didn't get one with the TV, they gave us a universal remote, but it doesn't work with it.

[vinceroger69]

Re: Atec av-420w 42" lcd tv

this is the place i used the otherday when i needed a odd one they did not list it but i contacted them and they sent one out that worked the set ok they maybe able to help?
http://www.avukltd.com/brand/Atec.htm