Just re-read this article after it was linked to today. Since my post above I had a similar case - a 42 inch plasma that was in a skip. I opened it and found the usual bulging caps. But that's when my problems started. They were as I recall 680uF at 400 volts. Not an easy cap to find. And to add insult to injury, some of them were under a part of the frame and could not be more than about an inch and a half high. Armed with these specifications I started to search...
I could get the right ratings - only in an 85C cap - but they were too high. I could get the right size, right capacitance, but only 250 Volts. I could get the right size, 400 V and 105 C, but only 250 uf.....and so on. Eventually my boss (this was at work) told me to get it out of the workshop or put it back in the skip. With a heavy heart I did the latter. I consoled myself with the thought that plasmas are kind of old technology now and it would have only added to my power bill, and it only had an analogue tuner so I'd have had to get a set-top box for it.
And my boss had the thrill of seeing me throw something in the skip. Which does not happen very often :-)
I am trying to remember what are the main failures of the LCDs we have repaired over the years... And I can tell you that usually its the inverter. Either some transformer is shorted or some other circuitry has failed.
I can't give you numbers because our management software doesn't allow us to categorize the repair work we do, but I think its less than 50%.
Yes, there are some LCD models that seem to have to some design flaw because most of them have bulged capacitors.
About the repair shop costs:
I agree with you about the way a repair shop should run its business.
As does my father that for more than 30 years as been doing exactly that.
There just one small difference: we can't give a quote, in most cases, without actually repairing the appliance.
However, we don't have employees therefore we don't have fixed costs.
And that makes all the difference; that's why most repair shops charge money to give a quote.
They can not afford to have on technician working all day on appliances that won't be repaired because the customer says it too expensive...
That IS the hard one to call, Rene. Basically when you don't think you'll get any further. Which will be a lot futher down the line for you in your garage than for a repair shop. The problems these days are (1) it's almost impossible to get service sheets and (2) unless you're kitted out for it, SMD components are very difficult to change.
But I reckon 90% of LCD / Plasma TV failures would be through-hole electrolytics which are easy to fix. I suspect a repair shop could do good business with these on the following basis:
- No quotes,
- If we fix it easily it's (say) $75.
- If we can't fix it easily, no charge
- If we reckon we can fix it with a bit more effort / parts etc, we'll quote, you can call it quits if you want.
I reckon you'd make enough on the ones with blown caps to cover your time on the others.....
I seem to always find the courage to open electronics that have failed on me prematurely, my problem is to determine when is time to call it quits, after you spend several hours in tear downs, replace and retest efforts.
It is hard to walk away from an investment of time and effort.
Does any one have a piece of wisdom that your willing to share, when is time to stop and recycle?
What brand and model flat panel TV?
I hope this is the exception not the rule for flat panels or we will all be using your example to fix our own flat panel TV's.
This is what happens when bean counters move engineering off shore without experence continuity.
Any real designer knows that you MUST derate SMPS capacitors by ~50%. (all caps need to be derated in any application, especailly electrolotics, and tantalums.)
Blog Doing Math in FPGAs Tom Burke 2 comments For a recent project, I explored doing "real" (that is, non-integer) math on a Spartan 3 FPGA. FPGAs, by their nature, do integer math. That is, there's no floating-point ...