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Main => Monitor/Video Forum => Topic started by: lilshawn on February 01, 2010, 05:43:57 pm

Title: Makvision 2425 UPDATE *fixed*
Post by: lilshawn on February 01, 2010, 05:43:57 pm

Makvision 2425 chassis found dead and ticking... HOT was replaced and still ticking.

anybody know which caps I could change out, none are obviously swelled. documentation is terrible...(the schematic is in 6 different pieces and the "service" manual is more of a "user" manual) parts are spread out all over the board, so it's hard to figure out what does what. can somebody give me a start...

also could the vertical ic (IC3) cause the power supply to do this too?

thanks in advance

Title: Re: Makvision 2425
Post by: grantspain on February 02, 2010, 05:16:23 pm

vertical deflection ic can cause this on other chassis

Title: Re: Makvision 2425
Post by: lilshawn on February 03, 2010, 01:04:11 am

i replaced a bunch of caps that i think are associated with the b+ (mainly the 200v ones) since the manuals I have are no help.

i'm picking up another driver ic tomorrow so hopefully....

i noticed that the old ic (ic3) when i removed it, had a really disappointing amount of heatsink grease on it.

almost as if someone used a small paintbrush to give it a single swipe. there wasn't really any transfered to the heatsink! I think if anybody has one of these (makvision or pentranic series) they might consider removing the chip and putting new grease on it.

Title: Re: Makvision 2425
Post by: lilshawn on February 03, 2010, 05:40:09 pm

well no such luck. still ticking on me. Why the heck do I get all the stupid chassis. :blowup:

checked out all the diodes again to be sure.

guess i'll shotgun a few more caps tomorrow  :banghead:

Title: Re: Makvision 2425
Post by: lilshawn on February 08, 2010, 01:43:48 am

replaced ic2 and now no longer clicking, just flat-lining, getting high voltage. changed HOT to be sure.

i'm not hearing any "high pitched oscillation"

checked for voltage at zd311 supposed to be 12.6v? but getting 0 (zero)

guess it feeds vcc to ic2

diode checks okay, working backwards tomorrow.... the saga continues

Title: Re: Makvision 2425
Post by: lilshawn on February 08, 2010, 11:29:39 am

fixed a broken wire feeding power to the diode, started up a few times now back to clicking again.  :banghead:

Title: Re: Makvision 2425 UPDATE
Post by: southmonitor on February 08, 2010, 05:10:56 pm

Question:
Was the HOT blown in the first place? I mean when you replaced it the first time was it blown?

Title: Re: Makvision 2425 UPDATE
Post by: lilshawn on February 09, 2010, 02:51:20 pm

Quote from: southmonitor on February 08, 2010, 05:10:56 pm

Question:
Was the HOT blown in the first place? I mean when you replaced it the first time was it blown?

no.

i have also found that if i disconnect the control panel wiring that is for the horizontal and vertical controls i can get the chassis to fire up and get high voltage... if i pull the power and reconnect the control panel again before the B+ has a chance to completely drain out i can get it started up again, with everything connected.

i'm thinking i still have a bad cap someplace. still searching.......

Title: Re: Makvision 2425 UPDATE
Post by: southmonitor on February 11, 2010, 08:16:19 am

I agree. Check on the small electrolythic caps around the sync generator IC. They should be 1UF/50V to 10UF/50V. Anyway check all the caps around that chip and in the Power Supply area. When they go bad the monitor doesn't start, specially those around the switching IC on the Power Supply area and they are the reason why the PS tick, tick, tick... More specifically there is a cap in the PS next to the SMPS chip (normally from 22UF to 100UF) that filters the  feedback voltage rectified from the switching transformer back into the chip to keep it running after it has started. If that cap goes bad, then there is not enough voltage to keep the chip running and therfore it goes off again and so on. That's why you hear the tick, tick, tick. Accordint to what you are saying that seems to be the problem.
Good luck
Adrian

Title: Re: Makvision 2425 UPDATE
Post by: Rickn on February 11, 2010, 07:34:43 pm

Here are a few hints...
2400 Series      
      
Width   C394   
foldover   R399   
27"   R392   Change to 470ohm
   R905   
Width    C912   
Power supply shutdown   C511   change to 220u
H Phase   C306   223J
27" Foldover   R336   change to jumper
Geometry/width   R904   Remove
   C908A   change to 224
   C908   
Stongly suggest C511 it is the start upcap change it to 220U.

Title: Re: Makvision 2425 UPDATE
Post by: lilshawn on February 11, 2010, 07:45:26 pm

thanks all,

haven't had much time in the past few days...i'm working on a touchscreen jukebox project that has to get on location soon, been having some issues with the usb touchscreen... quits working randomly. think i got it sorted out though....

i'll take another stab at it tomorrow... if the touchscreen still works in the morning... *crosses fingers*

i'll let everyone know what the dealio is  ;D

Title: Re: Makvision 2425 UPDATE
Post by: lilshawn on February 12, 2010, 11:41:51 am

Well I changed the c511 cap from the original 100uF to 220uF and it fired right up... going to try shutting it down and powering it up a few more times to make sure, but prognosis looks good.

thanks to southmonitor and Rick.... 10,000 internets for you! (pickup at front desk  ;D )