Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: scooby-doo on December 11, 2011,10:28:04
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All the caps were bulging, replaced....tv comes out of standby and I can hear static noise through the speakers, the set doesnt shut down, there is just no 24v from any of the pins on the psu I am getting 3v on the same connector block for the signal but thats my lot.
Any ideas people???
Thanks in advance.
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Not familiar with the set SD ...but Since elec caps were bulging ...now replaced ...and there is at least some invertor supply voltage ...I would back track from the connector ...and check any 24v supply diodes ...as this most likely (possibly a dual diode heatsink mounted) ...would have took a clogging ...
best of luck
Evan
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OOps misread your post I think ..
the 3v isn't from the invertor supply ?
So s/c supply diodes still look favourite ..
but ...does the set actually come out of standby ...? in fact is there a standby supply at all ?
rgds
Evan
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Hi S/D,
Don't think you mentioned known make or model - gives some problems, esp with no piccies - Chris
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Yes set comes out of standby...it seems to be working all ok apart from the 24v supply.
Will trace backwards later today...I did think earlier that a couple of the box type caps were a bit on the podgey side...but thought I may get away with replacing the electrolytic's for it to fire up....obviously not
But thanks for your help Evan
Oh yes the 3v Supply is on the inverter supply block....
Hi Chris its a Goodmans GTVL32W27HDF
Picture of PSU attached
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Looks like you have a couple of those double diodes on the right of the photo ..
D2010 etc ..
Highly suspect in this case I think ..
Usually find only 1 of the 2 in the package is gone ...
Hence still providing a DC output ..but shunted by a leak one ..
rgds
Evan
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Nice one Evan spot on...D2010 sc'd
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Sorry...removed from circuit short is still on the board D2010 is ok out of circuit
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hi
just a thought did you take the covers from the heat sinks
if you did they need to be put back on to complete circiut
dave
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Yes Dave left the heatsinks in situ...just removed the diode to check...and I am struggling to find this bloody short
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SCHOOL BOY ERROR WARNING :sign0144:
I blame my blow torch and plumbers solder.....I got solder splatter on one of the smd capacitors and resistors and it was causing a short.... :oops:
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SCHOOL BOY ERROR WARNING :sign0144:
I blame my blow torch and plumbers solder.....I got solder splatter on one of the smd capacitors and resistors and it was causing a short.... :oops:
It matters not buddy ...we've all done it at some time..
What matters is that you resolved it without permanent damage ..and the job gets done..
rgds
Evan
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Thanks Evan...I am full of them today...nearly smoked an LG I was working on today as I put the single pink inverter wire on the wrong way...that does make it smoke quite a bit.
Anyway back to this fault....I removed the short and fitted the board....I am getting voltage but its way too low, about 5volts from each 24v pin.....and the 3v has now dropped to 2.3v.
I thinks I fluffed it
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..Is that 5volts on load ...?
Whats the voltage with the invertor board disconnected ?
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Hi
Just checked again with and without inverter connected....the 3.2v is back and I have lost the low voltage on the inverter feed....Thats connected and disconnected
I have just checked all 3 pins of D2010 and not getting anything from that either
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Sounds like the invertor feed (24v) isn't being generated...
Often there is a seperate switch mode supply independant of the rest of the psu ..to generate the 24v ..
You say there is no longer a short on the 24v line after the double diode ..
Does this double diode read as a diode ..or does it read dead short left pin to centre ..and right pin to center ....when removed ...
If so its faulty ...
If it reads ok ..ie ..as A diode should ..
Low resistance one direction ..high resistance the other ...
Then I suspect the switch mode chip driving the transformer ..to generate the invertor supply to be non functional..
Its then a case of sourcing the switch mode surface mount chip ..and repacing ...plus its ascociated power FET ...or ...sourcing a new psu board ...which might be easier..
good luck ..
Evan
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No there is no short on either diode...good readings from both
I have noticed Andy (Ohm Supplies) has a repair kit for the psu but mentions a short on T2000 or blown IC2000 which is a surface mounted chip on the underside...will have a check on them now.
But thanks again for all your help Evan
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This unit is effectively two PSU's on one board. In your picture the top "half" of the board is for the low voltage supplies, the fact that you have "audio" proves that this is working. The bottom "half" in your picture is the 24v supply for the inverters.
The fault is most likely to be the electrolytic capacitor located between the "lower" yellow transformer and the right of the two heatsinks at the bottom. I think that it says C2056??? It is, from memory, 100uF/50v, and sometimes it has been encased in a short length of heatshrink sleeving and is easily missed. It can cause the picture (backlight) to be very slow to appear, sometimes for several hours after the set is switched on!!
You should also replace both of the 47uF electrolytics in the two PSU primary sides, and perhaps the two 680uF's which smooth the output of the 24v supply.
regards
Ken
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Cheers Ken
I have replaced 680's...I wish I had 24v to smooth :03: ...not replaced the one under the heatshrink as yet...nor did I bother with the two 47uf's have got some so will fit them after my cuppa tea.
The kit that Andy sells looks all on standby sides so that wont cure it.
Thanks Ken
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I'm pretty confident that replacing the 100uF under the heatshrink will cure it, let me know.
Regards
Ken
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Hi Ken ..
Nice to see you bringing your extensive knowledge here as well ..
Hope your suggestion fixes up S/Ds telly afore he tears his hear out ..
;)
rgds
Evan
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Yeahhhhhhhhh!!!!!!!!!!
Thank you thank you thank you....changed the extra three caps you mentioned and hoooorrarrrrr it only bloody works
I did notice the cap with heatshrink around while desoldering the tracks seem very fragile around that area probably because of all the heat off the tx, repaired and now works fine.
Thank you again
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Like I said..........
lol
regards
Ken
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And dont run off anywhere...A murphy problem coming
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Hi S/D,
What caps replaced ? have it as C2566 in Quuq files - always curious, but have few 'lol's' noted - due possibly to extreme age - Chris
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Hi Chris...Pic on page one of this post will help..cant remember all position numbers
These secondary caps were bulging
2 x 680f x 35v
2 x 1000f x 35v
Change these but looked ok
2 x 220f x 35v
The main culprit was like Ken mentioned the 100f x 50v at position C2056 its not C2566
I also replaced 2 x 47f x 63v...I did get 24v back without changing but didnt want them to feel left out so changed them anyway
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Hi S/D and thanks,
Could appear 'In the know' next time the prob reported - like you, tend to change most every wet cap in the hot area just to be on the safe side - Chris