KV Probs i.e no Power suply

[jambutty]

On most KV's that end up with No Power or 1 Green dot, in the majority it is usually down to a faulty capacitor, below is my easy method on how to test for a fualty one.

Testing a Capacitor.
Capacitors store energy to provide power to electrical appliances. The capacitors can, over time, lose their effectiveness to power the appliance. You can test them to determine whether or not they are still good.

Step1 Remove the suspected faulty capacitor from the unit. If it's a high powered capacitor, it will still
hold a high charge, Discharge the capacitor by using a metal screwdriver with a handle that's insulated.
Touch the metal end of the screwdriver to both metal terminals at the same time to discharge any power left
in them. (This will prevent you getting an electric shock, Ouch)

Step2 Turn on the capacitor tester/or Multi Meter and make sure it's getting power. Plug in the tester probes according to
the instructions on the meter. Set the selector to an OHM scale before testing the capacitor. Some meters
will have an OHM setting pre-set for you.

Step3 Touch the leads together so that the meter will zero out on the meter.

Step4 Note where the meter points to before touching the wires to the capacitor. Then touch the terminals of
the capacitor with the red probe, which will go on the left, and the black probe which will go on the right.

Step5 Watch the pointer on the meter. The needle should move away from the left side, or the infinity, and
veer toward the right before returning to the infinity. It should move further to the right when the probes
are reversed. This means the capacitor is good. If the needle goes all the way to the right side and doesn't
return to the left, or infinity side, the capacitor is bad, or it has shorted out.

If the meter needle goes all the way over to the right side and stays there then THIS is the shorted capacitor, Replace it, but also remove and test c11 an c12 cos one or both of these may have shorted as well.

[jambutty]

Most likely Fualty Capicitors (I've took some pics inside my KV) as I have stated previously the most likely capacitors to have shorted on the KV boxes are c10-c11 OR c12, someone asked for a pic of the most likely shorted capacitor but forgot who it was..
OK I have the pics with the likely duff Capicitors BUT I don't know how to upload files to this site, if anybody want's the pics then just pm me with yer email addy and I'll zip em to yer.

PS when yer look at my scans you will see I have marked the Capicitors with a red flash mark showing the Capicitors, once yer get these jpgs I sugest that you remove C10 first near the transformer (Got yellow tape round it) test this one first, if OK then remove c11 & c12 and then test these, it's most likely 90% one of these 3 that's shorted, follow my instructions Testing Capacitors with yer multi meter and then if it's one of these 3 Capicitors then just replace it and yer up and running again with a repaired KV.
Don't forget to hit the thanks when yer repair yer dead kv back to life with these easy tips from Jambutty.
AJ

[gadgetfiend]

nice guide easy when you know ehow eh ?

[jambutty]

nice guide easy when you know ehow eh ?
Thanks for the comments mate.

Just another quick one on this subject of blown KV's, I'm no expert myself and I have never had to test Caps on a KV before but it's just something I read once that Caps 10-11 or 12 are the suspect ones that seem to short out most (I did send 2 dead kvs back to supplier a while back but I didn't know how to test Capacitor's then) wish I had a blown one now cos I would love to test this out myself.
OK for anyone not fluent on testing caps then as far as I know, unless you have a really good Capacitor Tester (these seem quite dear, I looked on Amazon once and think cheapest one was £160) reason these are brilliant is beacause you don't have to remove the Capacitors from the circuit to test them.
The trouble with a bog standard Avo or multi meter reader is that you have to unsolder and remove the suspect Capacitor first and then test them to get an accurate true reading because as far as I am aware if you test a Capacitor while it's still in the circuit, you don't get a true reading i.e. you could be testing a blown Capacitor and it may show that it's good when it is most likely shorted, I think the reason is that if you test a Capacitor while still in the circuit, it may be sharing with a good Capacitor somewere and then it will read out that the Capacitor you are testing is good when it may be a shorted one cos it's sharing with a Capacitor thats OK.
OKAY if anyone can add any further help on this subject then please post it on this thread and also is someone does get a chance to test a blown KV and gets it up an running then please post how you did it as I only suggested testing Capacitor's c10 c11 & c12 when in fact it may be a different Capacitor or some other componenet that's blown, this will be a great help for us all if we can get more ino and help on Blown KV's cos one day your own my stop working and with any tips or help on a repaired KV it will save us all forking £30-£40 to a tv engineer to repair it when we may be able to repair one ourselfs.
AJ.

[yusuf_gaz]

Hi

Today I tried this repair but I didnt test any components prior as didnt have equipment.

Changed c11 and c12 and the fuse, didnt change the c10 blue cap as maplins didnt have that but said it seems allright if it had failed it would have been split.

So I put the new caps, fuse and the old c10 - doesnt work for me, is there anything else that could need changing. The fuse I changed was the internal fuse on the power board.

Regards

[jambutty]

Today I tried this repair but I didnt test any components prior as didnt have equipment.

Changed c11 and c12 and the fuse, didnt change the c10 blue cap as maplins didnt have that but said it seems allright if it had failed it would have been split.

So I put the new caps, fuse and the old c10 - doesnt work for me, is there anything else that could need changing.

Right c'mon you tech guys out there who know more than me on how to repair a dead KV and test Capacitors (IF it is a Capacitor that's blown), Yusuf as had a go at doing one but No joy, so lets all get together on this and help each other cos before long someonelse is gonna get a blown KV and won't it be great if we can manage to get one repaired with help on this great site of ours, like I say I'm no expert on repairing stuff but it's just something I read about somewhere that KV's seem to blow due to faulty Caps, c10-c11 or c12, but Yusuf as tried and no joy, so what's the next thing he can try, someone must be ble to help out on this, so get some help posted on what else we can try apart from Caps 10-11 & 12, is it a differenet Capacitor or a different component, as a transformer blown or something else.
Let's all get this sorted and it'll be great when some guy posts a thread here to say he's got a dead KV up an running and tells us how he did it!

Someone may know a TV engineer they could ask help for on this issue!
AJ

[yusuf_gaz]

Hi

What I can say is these power supplies are very hard to source as I been trying for a while now and have posted on other forums without much joy and contacted a few traders.

So if this thread helps to identify how to repair or which particular caps would benefit people in future then I will try and contribute.

Over the course of this and next week will try and change other caps to see if it helps this thread and myself of course.

This has prompted me because of the thread started by jambutty otherwise box mat have stayed in corner until I found another power supply.

[jambutty]

Just one other point that may help out on this (Probably a long shot) but does anyone have a circuit diagram for the KV, prob top secret this but worth asking.
AJ

[jambutty]

Here is another thing to try if after testing the Capacitors and they are ok.

Test the Diodes as well.Don't forget to Discharge the Filter Capacitor first, Power off on KV then touch both prongs of the filter cap to discharge it.
Next You have to unsolder the diode from the circuit board, (try the diodes near the transformer first) or you can just unsolder 1 leg and then test it, set your tester to the diode symbol and then it should only read 1 way, then reverse the black/red test leads on you reader and if it reads both ways then the diode has shorted.
So if it reads only 1 way then diode is good, if it reads both ways then diode has shorted.
worth a test.

[yusuf_gaz]

Hi

Thanx for that ok will try it see how it goes.

Anybody have any thoughts/input on this.

Regards