electronics, repairs, service manuals and datasheets discussion community for the repairs professionals and technicians
FAQSearchMembersGroupsRegisterProfilePM'sLogin/Out
Gateway VX1120 horizontal lines on top
Goto page 1, 2  Next
 
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Equipment Repairs
View previous topic :: View next topic  
Author Message
aleksazr



Joined: 26 Apr 2015
Posts: 9

PostPosted: Sun Apr 26, 2015 7:27 am    Post subject: Gateway VX1120 horizontal lines on top Reply with quote

Hi all, this is my first post here.

I was given (for free) a Gateway VX1120 CRT monitor a few years ago.

It had two problems, the color RED was missing at times and the whole
screen could go black. Those two I have fixed, even though I have very
little knowledge of electronics in general (by soldering bad joints).

But now I have a third problem, there are horizontal lines on top of the
screen, for which, as I have googled it, is responsible one capacitor,
his ESR has changed. Which one?

I've opened the monitor in hope the capacitor has changed his outer
appearance, but no luck... and my knowledge ends here Smile

If someone knows which one it is, I'll take some pictures of the inside
of the monitor, so he/she can circle it on the pic.
Back to top
View user's profile Send private message
torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Mon May 04, 2015 3:01 pm    Post subject: Reply with quote

I dont know any exact details of just that monitor, but if you look at a typical vertical output stage built with bipolar transistors (usually within an IC), there is a so-called bootstrap capacitor, which serves to make sure that the "upper" transistor in the complementary output stage gets good base drive during the retrace. For instance, looking at a schematic with the old IC TDA1170S http://elcomp.ru/images/catalog/tos/tda1170s.gif , it is the 100 uF capacitor connected between pins 3 and 5.

I think you can easily locate that capacitor if you check out what IC is used for vertical deflection in your monitor, and then look in the datasheet for that IC.

For the sake of completeness, the same kind of error can be caused by the flyback diode (1N4001 connected between supply voltage and pin 5 in the TDA1170S schematic, sometimes integrated in more recent ICs), but that is more seldom.
Back to top
View user's profile Send private message
aleksazr



Joined: 26 Apr 2015
Posts: 9

PostPosted: Mon May 04, 2015 4:52 pm    Post subject: Reply with quote

Thanks!

IIRC there are two ICs inside (that I saw):

one on the horizontal PCB on the bottom (DIP, around 40 pins),

and one on the back of the tube, a smaller, vertical PCB. (DIP, around 32 pins).
That is the one I have re-soldered to fix the black screen problem.

I'll open the monitor in a few days.
Back to top
View user's profile Send private message
aleksazr



Joined: 26 Apr 2015
Posts: 9

PostPosted: Tue May 05, 2015 7:50 am    Post subject: Reply with quote

The DIP 32 is M52746SP

Could it be that one? The DIP40 IC is not easy to access...
Back to top
View user's profile Send private message
torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Tue May 05, 2015 8:10 am    Post subject: Reply with quote

No, i think the vertical output IC will be a single-in-line part with about 10 pins, mounted to a heat sink. Probably you will find it near the wiring to the deflection coils.
Back to top
View user's profile Send private message
aleksazr



Joined: 26 Apr 2015
Posts: 9

PostPosted: Tue May 05, 2015 8:13 am    Post subject: Reply with quote

The DIP40 is actually DIP56 ST72771N9B which is a MCU.

There is also this one M35071

There is one more IC that I can't get to, yet.
Back to top
View user's profile Send private message
aleksazr



Joined: 26 Apr 2015
Posts: 9

PostPosted: Tue May 05, 2015 8:21 am    Post subject: Reply with quote

torbjorn wrote:
No, i think the vertical output IC will be a single-in-line part with about 10 pins, mounted to a heat sink. Probably you will find it near the wiring to the deflection coils.


This one?
http://www.ti.com/lit/ds/symlink/lm2402.pdf
Back to top
View user's profile Send private message
torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Tue May 05, 2015 9:38 am    Post subject: Reply with quote

No, none of these. I think it should be placed on the main PCB, not at the CRT socket. The casing is probably similar to that of the LM2402.
Back to top
View user's profile Send private message
jts1957



Joined: 24 Nov 2008
Posts: 2472
Location: Far, Far Away

PostPosted: Tue May 05, 2015 10:18 am    Post subject: Reply with quote

Possibly IC401(LA7841L) ?
_________________
You're over there, I'm over here.
Back to top
View user's profile Send private message
aleksazr



Joined: 26 Apr 2015
Posts: 9

PostPosted: Tue May 05, 2015 11:48 am    Post subject: Reply with quote

jts1957 wrote:
Possibly IC401(LA7841L) ?


I've found IC401, but it is TDA9309 not LA7841L.

Is that the one? If so, is it between pins 3 and 5, or 3 and 6?
If it is, I'll have to unscrew every screw there is Smile
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Equipment Repairs All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Електроника София - Service Manuals Free Download - Prikachi - Service Diagrams

Free TV Schematics Download - HARDW.net - Pinout Master - Jabse Search - Jabse.InK  - Pulsator

Connector Pinout Forum - Новини - SnimkiOt.com - безплатен DNS - Whois разузнаване - Poblizo.com : пътешествия