Ctx S772a

[adzie21]

Hello , i have read a thread on a similar item but i thought id start my own as the power boards look different. i got given a CTX S772A knowing it didnt work but i powered it up and i could hear a buzzing noise coming from some area near the large capacitor. now am i right in thinking that this could be all thats is wrong? it trys to turn on the speakers click then it goes dead could the capacitor not be charging to deliver a constant flow? on the other hand with a little work i assume it would be possible to "make" another power source? i studied electronics for a short time but i need some expert advise. please dont think im stupid i really need some help..


Adam

[adzie21]

Re: Ctx S772a

[PlainBill]

Re: Ctx S772a

Hello , i have read a thread on a similar item but i thought id start my own as the power boards look different. i got given a CTX S772A knowing it didnt work but i powered it up and i could hear a buzzing noise coming from some area near the large capacitor. now am i right in thinking that this could be all thats is wrong? it trys to turn on the speakers click then it goes dead could the capacitor not be charging to deliver a constant flow? on the other hand with a little work i assume it would be possible to "make" another power source? i studied electronics for a short time but i need some expert advise. please dont think im stupid i really need some help..


Adam

1. Read this thread on attaching pictures to a post. I am petitioning Dante to add a 10th circle to Hell.

2. You also seem to have saved the pictures in some format Paint can't handle. I had to filter it through Vueprint. I just about decided to ignore the thread.

3. I count 5 obviously bad caps (red circles), three suspect caps (orange circles), and one good cap (green circle) that should all be replaced. The total cost would probably be under $10.00.

Or you can design and build a new power supply.

PlainBill

[adzie21]

Re: Ctx S772a

Thank you , for your help. sorry about the enormous pics. im sort of a noob at posting pics.

[EGuevarae]

Re: Ctx S772a

Thank you , for your help. sorry about the enormous pics. im sort of a noob at posting pics.

1.- Welcome to the forums.
2.- Be nice with Bill and he'll be nice to you - post in the suggested way and in a format we can easily manipulate/edit.
3.- You are not stupid because you ask. Those who do not ask are at risk of being stupid all their life. Just don't ask the same over and over again, because that is a different story.
4.- Read the caps, and post back the brand (Samxon, CapXon, etc.), series (GL,KZG, GX, etc), V Rating (16v, 25v, 35v, etc) and capacitance (820uf, 1000uf, etc.) so proper advice can be done on replacing them. And as Bill said, Replace them all, it is worth the like $10 you'll spend.

Eduardo

[adzie21]

Re: Ctx S772a

ive got the replacements but the originals are capxon 470uf 25v and the guy in the shop sold me 470uf 35v is this ok? plus i need to find a 100uf 400v cap too. thats eveyone for your help hopefuly this will sort it

[PlainBill]

Re: Ctx S772a

ive got the replacements but the originals are capxon 470uf 25v and the guy in the shop sold me 470uf 35v is this ok? plus i need to find a 100uf 400v cap too. thats eveyone for your help hopefuly this will sort it

It usually not necessary to replace the 100uF, 450 V cap.

The higher voltage (35 vs 25 volts) is not a problem, provided the caps fit, and a re low ESR. What caps did you receive?

PlainBill

[adzie21]

Re: Ctx S772a

It usually not necessary to replace the 100uF, 450 V cap.

The higher voltage (35 vs 25 volts) is not a problem, provided the caps fit, and a re low ESR. What caps did you receive?

PlainBill

the caps i got to replace are Nic NRSA 35v 470uf ce 85'c as printed on them. they guy in the shop pulled some of the plastic off the big cap trying to lift it up and said it needed to be replaced because of that. then he found he didint have any! now ive got a messed cap i didnt need to replace.

(second edit: the caps are low esr)

[adzie21]

Re: Ctx S772a

I have some more info on the big cap and thought i would post it while i was thinking about it.this is the cap i think i need.

[Radio Fox]

Re: Ctx S772a

the caps i got to replace are Nic NRSA 35v 470uf ce 85'c as printed on them. they guy in the shop pulled some of the plastic off the big cap trying to lift it up and said it needed to be replaced because of that. then he found he didint have any! now ive got a messed cap i didnt need to replace.

(second edit: the caps are low esr)

Those caps are not low ESR, and they are not high temp. You need 105°C types.

I always get Panasonic FM (or FC as a 2nd choice) from Radio Spares (RS), as I'm in the UK.

I assume you're in the USA. If you list all the caps you need (I can see at least 2 different sizes in your photo), then perhaps someone can give you a pointer as to what to order from Digikey.

Is the big cap actually damaged, or is it just the plastic sleeve that has peeled off? It might still be OK if you stick it down again.

[EGuevarae]

Re: Ctx S772a

... If you list all the caps you need (I can see at least 2 different sizes in your photo), then perhaps someone can give you a pointer as to what to order from Digikey..

That's what I suggested. Post the info

[seanc]

Re: Ctx S772a

It's worth seeing if the 100uf 400v is bulged.

The last dead & buzzing thing I had was a 3Com 24 port switch. Mains cap was dead, as were a few smaller 220uf 50v and 100uf 25v caps.

[adzie21]

Re: Ctx S772a

i am from the uk too. i have both types needed and have been told they are alright. its just the plastic that is peeled on the big one. i was only given the monitor so im not going to spend too much on it. ill replace the caps tonight and see what happens. my bad they are not low esr, just general use. i am still learning so bare with me.

[PlainBill]

Re: Ctx S772a

i am from the uk too. i have both types needed and have been told they are alright. its just the plastic that is peeled on the big one. i was only given the monitor so im not going to spend too much on it. ill replace the caps tonight and see what happens. my bad they are not low esr, just general use. i am still learning so bare with me.

Hey, I'll keep my clothes on, you do the same, please.

PlainBill

[EGuevarae]

Re: Ctx S772a

Hey, I'll keep my clothes on, you do the same, please.

PlainBill

[adzie21]

Re: Ctx S772a

lol fair enough great news thanks to PlainBill who suggested the faulty caps i replaced them and all works fine now! thanks everyone for your help. i hope this thread may help someone else.

[EGuevarae]

Re: Ctx S772a

... all works fine now! ....

[Radio Fox]

Re: Ctx S772a

lol fair enough great news thanks to PlainBill who suggested the faulty caps i replaced them and all works fine now! thanks everyone for your help. i hope this thread may help someone else.

Just keep in mind that the fix probably wont last very long using those caps, but at least you now know for sure what the problem was.

[waanzin]

Re: Ctx S772a

Hello I'm new to the site, just wanted to say thanks to you guys.
Someone gave me this exact screen for free because it was broken. Found this post and just finished changing the 470uF caps and it works again. I found 4 50V 105+°C caps in my collection but I'm going to upgrade the screen with active cooling anyway :p

Do you guys think overheating is the only possible reason for the failures of the caps? Just to know I'm not wasting my time with the active cooling.

anyways thanks guys, nice site, cheers


Nick

[PlainBill]

Re: Ctx S772a

Hello I'm new to the site, just wanted to say thanks to you guys.
Someone gave me this exact screen for free because it was broken. Found this post and just finished changing the 470uF caps and it works again. I found 4 50V 105+°C caps in my collection but I'm going to upgrade the screen with active cooling anyway :p

Do you guys think overheating is the only possible reason for the failures of the caps? Just to know I'm not wasting my time with the active cooling.

anyways thanks guys, nice site, cheers


Nick

Heat doesn't help, but the root cause was inferior quality caps. It's an example of positive feedback. The significant characteristic is ESR (equivalent series resistance).

Think of it this way - the purpose of a capacitor is to store energy from the power supply and release it when needed. The lower the ESR, the less energy is wasted in the process. Heat accelerates aging. As caps age the ESR rises, so more of the energy being pumped into and drawn out of the cap is lost as heat. This increases the speed at which they age, the ESR goes higher, more heat is generated. Eventually the cap gets so hot it vents, then the electrolyte drys out, the capacitance drops, compounding the problem.

Certain brands of caps have a reputation for failing quickly, others have a reputation for lasting a long time. Putting a cooling fan will help your monitor last longer (until the fan bearings dry out). Spending a few bucks more (or sometimes less!!!) for quality caps will have the same effect.

PlainBill