WG 25" K7400 curved edge problem

[Gamemaster86]

Hi,

I'm after some advice on how to fix an issue with my monitor. Both the left and right edges towards the middle of the edge, are curved. Meaning to get to a stage where I don't see it I have to stretch the screen and lose part of it. Has anybody seen this issue before and fixed it? I have tried adjusting the keystone / pincushion control on the back but to no avail.

Here are pictures of the issue.

Thanks for looking.

[Gamemaster86]

Another thing I thought was odd is that the 25" K7400 chassis doesn't mention having a pincushion adjustment board in the manual - could this have been a late addon?

Also if I reduce the H-Size all the way down it turn the whole thing inwards to create a pincushion.

Anybody seen a problem like this before?

[Gamemaster86]

I've now found it's not just the edges of the pictures that have bent lines, but also edges of windows etc. It's shown better in the pics.

Can anybody recommend a potential fix or repairer located in England?

Thanks

[ed12]

yes
a few things will cause that problem
poor power requlation,or a leaky horz coupler cap,or your yoke is going south
u must chk the first 2 first
the small add in board was put in for certian game use
as a rule i remove them,as my games run 1 res.

ed

[Gamemaster86]

yes
a few things will cause that problem
poor power requlation,or a leaky horz coupler cap,or your yoke is going south
u must chk the first 2 first
the small add in board was put in for certian game use
as a rule i remove them,as my games run 1 res.

ed

Thanks for the reply 

Sorry to sound like a newb but how would I go about checking the first two?

[ed12]

a few things first
the newb is a no nomer here
second do u own a mulitmeter ?
third do u have the service manual ?
if so look for the :test: points
and meter them
they have to be within a 10%  range
so this would equal 165-10%=about 163
much like that
start there

ed

[Gamemaster86]

Hi,

Yes I have the manual and the schematic links are here http://www.wellsgardner.com/pdf/Schematics/K7400_25_inch.pdf and here http://www.wellsgardner.com/pdf/Spec/K7400_25.pdf

The trouble is I can't see any points called :test: any idea where and which points I'd need to check?

I presume I'd be measuring resistance?

[ed12]

hi
in the manuals they are listed as tp101/102/103 etc
the point here is >tp<
and it will state dc or ac volts
make sure as i explained they are within range

ed

[Gamemaster86]

Ok, so I can see a few TP 'test points' on the schematic but can't see any voltages next or near to a test point. Take for instance tp 103 and tp 104 located in square 6B, it doesn't have a voltage near them.

Thanks

[lilshawn]

sigh...  you go to the bother of linking the schematic and spec sheet, but glaze over the voltage reference charts right next to them?!

http://www.wellsgardner.com/pdf/voltage/K7400_K7500.pdf

[Gamemaster86]

sigh...  you go to the bother of linking the schematic and spec sheet, but glaze over the voltage reference charts right next to them?!

http://www.wellsgardner.com/pdf/voltage/K7400_K7500.pdf

Apologies, this list wasn't in my collection.

Thanks for posting.

[lilshawn]

Grab everything for your monitor and read it, especially the "service manual" (k7500/u5000 is basically the same chassis). It has a step by step for just about every adjustment on there. It even goes as far as how to adjust the convergence. (which not a lot of instructions exist for that as it was a manufacturer done thing, not to be done out in the field.) Theory of operation...best way to learn how things work is by learning the theory of operation. once you know that, you can easily troubleshoot issues.

Best manual ever. 

[Gamemaster86]

Thanks :-)

Looks like I have some reading to do.

Will report back if I come up with anything.

[ed12]

hi
there is 4 test points of interest
they are all dc

tp202
tp203
tp204
tp205

hone in on them

ed

[Gamemaster86]

Ok so after some more tested i'm pretty sure it's not the yoke as i've tuned both the static and dynamic convergence and still have the bent lines.

Will now test the points mentioned. A few more questions and I should be able to get going :

1. I am presuming I will need to have power to the chassis in order to test the voltages?
2. I'm guessing that the points will be underneath so thats means discharging the tube and removing that correct?
3. Lastly am I right in saying that to check the voltages I test from the TP to the next black dot next to it on the diagram?

Thanks for the assistance.

[ed12]

a tp is always refed to ground

u should beable to tell the tp from the top of the chassic
just look the schematic over and see where it comes from
ie r101 lets say hook's to tp101 and carrys on into the circuit
u can test it right there
and so on

btw conv dynamic and or static will not tell if the yoke is going south
do the tp tests first,then get back to us


ed

[lilshawn]

no, it should have a tiny little post soldered into the board. some didn't though so you'll just have to follow the schematic to the next part...capacitor or diode or resistor....something with a bare leg you can probe.

if you are skittish about poking around 300+ volts then get a wire with some alligator clips on it and clamp it on there and power it up and take your reading with it all hooked up.

[Gamemaster86]

Great tips, thanks guys 

Will report back with my findings.

[Gamemaster86]

Luckily I have the tiny soldered posts which made it easy to connect the probe. Even with the schematics finding the points wasn't easy though.

Ok values are as follows :

TP202 = 124.3 V  ------Listed Typical Voltage = 117.20 V
TP203 = 148.0 V  ------Listed Typical Voltage = 152.00 V
TP204 = 15.46 V  ------Listed Typical Voltage = 14.70 V
TP205 = 24.32 V  ------Listed Typical Voltage = 24.50 V

TP202 looks suspect?

[ed12]

202 and 203 look a tad off
it might cause that problem
come back from 202 and do some value testing
power off of course

ed

[Gamemaster86]

Sorry i'm going to need some more hand-holding here.

With the power off am I measuring resistance.

Where and how do I test backwards from that point then?

I've attached the area around TP 202 for reference.

Thanks

[ed12]

maybe  lilshawn
can help a little here
but when u look at your schmeatic
u c the j13 and j14,unless my mind is making a south turn i think that is a horz width point?
>by boosting the b+ on tp202<
which with 200v caps should be in the 175 range
it might even make refernce to it in the manual


ed

[Gamemaster86]

I've reduced the B+ using VR101 so that TP202 reads 117v as it should. It however made no difference to the bent vertical lines. 

[lilshawn]

can you re-measure the test points now that youve tweaked the b+?

if its up where it should be we can look elsewhere, otherwise something running off tp203 is loading it down.

sorry been a bugger of a day.

[Gamemaster86]

Sure I'll check them all again when I get home tonight.

No problem, just appreciate the help.

[Gamemaster86]

Ok So voltages are now as follows :

TP202 is now 117
TP203 had now reduced down to 137.8
TP204 is now at 14.72
TP205 is at 23.46

Pre B+ adjust

TP202 = 124.3
TP203 = 148.0
TP204 = 15.46
TP205 = 24.32

So TP 202 is now in line but TP203 has now reduced down even further than the recommended 152. TP204 is now as it should and TP205 is now a little lower than recommended.

[lilshawn]

lets get good voltages first.

replace:

C310
C812

they are both directly related to the voltages on TP203 which is low now. I would actually recommend replacing all the 'lytics, but these are likely the cause of that voltage being low.

[ed12]

yes yes yes
get the voltages sorted out first
thk-u  lilshawn

ed

[Gamemaster86]

Update:

So I have had the chassis tested and a few of the caps replaced. It appears to be fine when connected to a different tube, pic attached.

I do however feel a bit of an idiot, it appears that my monitor is one of the rarer wg 23k7401 models. I know, 23" wells gardner not usual but it does exist and seemingly only in the sammy atomiswave cab. I found someone on a different forum who took pics http://forums.arcade-museum.com/showthread.php?t=253955

THis would explain the strange yoke reading I reported in my other thread.

So now that i'm pretty sure the chassis is ok, i've also checked the coils in the yoke and could see no problems - all shiny and clean.

Any more ideas?

[Gamemaster86]

Any more ideas 

[lilshawn]

 

I got nothin'

if it works on another tube, perhaps there is a small difference in the induction value of the yoke that is throwing things off. There is a way (of which i have absolutely NO idea how to do)  to add or subtract value from certain caps to tweak the scan. You may end up blowing up the chassis or yoke though. You may have to just live with it.

get some games on that monitor and play away. You'll never notice. Trust me.

[ed12]

i tried to explain this to u in no unceritan terms
the restinance means squat..in the horitizal frez range
it is induntance..hence the list..please pay attenion
if u are out by 2 mill-heneres it will do that exact problem
the yoke will fire up for u but once it heats a tad >10-30< sec's will through the horz freq out,if u had a scope u can clearly see it >shift<

ed