need help with odd CRT monitor image

ive got a tovis mtg-1901cn cga color monitor. in use, or with a test pattern, the image starts out perfectly at the top. as you move down toward the middle , it gradually starts to compress the image, with more compression the closed you get to center. and when it gets to mid screen, its a full vertical collapse. bright while line across the center, with no image whatsoever in the lower 50% of the screen. also sold as a vision pro .

battery voltage is good at 123, 12v and 24 v are good. 123 volts at the flyback.
the vertical output ic is a LA7833. pin 6 has good 24 volt supply, and pin 2 ( output) is a nice 24 v square wave. i recapped the monitor, and the image is exactly the same. now im stuck.

thanks

 

[John-Del]

On Tuesday, July 4, 2017 at 8:44:59 PM UTC-4, mhoo...@gmail.com wrote:

ive got a tovis mtg-1901cn cga color monitor. in use, or with a test pattern, the image starts out perfectly at the top. as you move down toward the middle , it gradually starts to compress the image, with more compression the closed you get to center. and when it gets to mid screen, its a full vertical collapse. bright while line across the center, with no image whatsoever in the lower 50% of the screen. also sold as a vision pro .

battery voltage is good at 123, 12v and 24 v are good. 123 volts at the flyback.
the vertical output ic is a LA7833. pin 6 has good 24 volt supply, and pin 2 ( output) is a nice 24 v square wave. i recapped the monitor, and the image is exactly the same. now im stuck.

thanks

Sounds like a shorted turn in the deflection yoke, but not sure what you mean by a square wave on the output.

 

[John Robertson]

On 2017/07/04 5:44 PM, mhooker32@gmail.com wrote:

ive got a tovis mtg-1901cn cga color monitor. in use, or with a test pattern, the image starts out perfectly at the top. as you move down toward the middle , it gradually starts to compress the image, with more compression the closed you get to center. and when it gets to mid screen, its a full vertical collapse. bright while line across the center, with no image whatsoever in the lower 50% of the screen. also sold as a vision pro .

battery voltage is good at 123, 12v and 24 v are good. 123 volts at the flyback.
the vertical output ic is a LA7833. pin 6 has good 24 volt supply, and pin 2 ( output) is a nice 24 v square wave. i recapped the monitor, and the image is exactly the same. now im stuck.

thanks

Your vertical circuit is missing the bottom deflection half of the
vertical circuit. If the vertical driver is an IC, replace it, if it is
a pair of transistors then I would suspect the transistor pulling to
ground (typically the lower of the two on schematics) is the one at fault.

The vertical drive is just a very slow audio amp, apply audio amp
service methods.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
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"Old pinballers never die, they just flip out."

 

And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²

 

[John Robertson]

On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:

And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²

Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:

On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse..

thanks much

 

On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:

On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

 

[John Robertson]

On 2017/07/05 10:00 PM, mhooker32@gmail.com wrote:

On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

Any schematic you can provide a link to? Someone suggested a bad yoke,
which is possible if the bottom half of the vertical deflection shorted
out. Maybe. However a schematic would help.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[rickman]

mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:

On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that this is
only 12 volts, maybe the diode?

--

Rick C

 

On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:

mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image.. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt supply..
Measure the 24 volt supply at pin 6. I bet something is wrong that this is
only 12 volts, maybe the diode?

--

Rick C

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage. looks like a few transistors are after the vertical ic, i'm looking at them now. not real good at following this schematic, so any help is appreciated.

thanks

 

[rickman]

mhooker32@gmail.com wrote on 7/6/2017 11:18 AM:

On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that this is
only 12 volts, maybe the diode?

--

Rick C


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage. looks like a few transistors are after the vertical ic, i'm looking at them now. not real good at following this schematic, so any help is appreciated.

I'm not so good at following this schematic myself. It looks like W402 is
the connector to the yoke. If so, I would say Q404 sets the vertical
position. Q360 and D307 link the vertical drive signal to I201, the color
gun controller. Perhaps this is creating too large a load from a bad part,
so the drive is clipped?

Did you say I302 pin 2 has a square wave on it? Shouldn't that be a sawtooth?

--

Rick C

 

[Jeroni Paul]

mhoo...@gmail.com wrote:

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage. looks like a few transistors are after the vertical ic, i'm looking at them now. not real good at following this schematic, so any help is appreciated.

thanks

In the yoke there are two coils for vertical and two for horizontal connected in series or parallel depending on the design, if in parallel one coil connection could be broken. The coils are connected together in the solder posts on the yoke, you may check there if some wire looks loose.

 

On Thursday, July 6, 2017 at 2:47:59 PM UTC-4, Jeroni Paul wrote:

mhoo...@gmail.com wrote:
https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage. looks like a few transistors are after the vertical ic, i'm looking at them now. not real good at following this schematic, so any help is appreciated.

thanks

In the yoke there are two coils for vertical and two for horizontal connected in series or parallel depending on the design, if in parallel one coil connection could be broken. The coils are connected together in the solder posts on the yoke, you may check there if some wire looks loose.

thats a great idea, i didnt know the coils were doubled up. i will check that for sure tonite. i was thinking of inverting the image, there are solder pads for an inverted header on the chassis board, and see what the image does. that would tell me if its the yoke or a chassis issue. does that make sense?

thanks much

 

[John-Del]

On Thursday, July 6, 2017 at 11:18:38 AM UTC-4, mhoo...@gmail.com wrote:

On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that this is
only 12 volts, maybe the diode?

--

Rick C


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage.

Not saying the yoke is the problem, but a single turn shorted to an adjacent turn will not change the resistance reading on your dmm, but a single shorted turn will totally collapse the magnetic field of the coil.

A ringer is the best instrument to check for shorted turns.

 

On Thursday, July 6, 2017 at 3:58:22 PM UTC-4, John-Del wrote:

On Thursday, July 6, 2017 at 11:18:38 AM UTC-4, mhoo...@gmail.com wrote:
On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that this is
only 12 volts, maybe the diode?

--

Rick C


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage.

Not saying the yoke is the problem, but a single turn shorted to an adjacent turn will not change the resistance reading on your dmm, but a single shorted turn will totally collapse the magnetic field of the coil.

A ringer is the best instrument to check for shorted turns.

not sure what a ringer is, but im pretty sure i dont have one. you mean like a tone generator, and you move it around the yoke ?

 

[Ian Field]

"John Robertson" <spam@flippers.com> wrote in message
news:9vOdneJtZoCTHsHEnZ2dnUU7-WXNnZ2d@giganews.com...

On 2017/07/04 5:44 PM, mhooker32@gmail.com wrote:
ive got a tovis mtg-1901cn cga color monitor. in use, or with a test
pattern, the image starts out perfectly at the top. as you move down
toward the middle , it gradually starts to compress the image, with more
compression the closed you get to center. and when it gets to mid
screen, its a full vertical collapse. bright while line across the
center, with no image whatsoever in the lower 50% of the screen. also
sold as a vision pro .

battery voltage is good at 123, 12v and 24 v are good. 123 volts at the
flyback.
the vertical output ic is a LA7833. pin 6 has good 24 volt supply, and
pin 2 ( output) is a nice 24 v square wave. i recapped the monitor,
and the image is exactly the same. now im stuck.

thanks


Your vertical circuit is missing the bottom deflection half of the
vertical circuit. If the vertical driver is an IC, replace it, if it is a
pair of transistors then I would suspect the transistor pulling to ground
(typically the lower of the two on schematics) is the one at fault.

The vertical drive is just a very slow audio amp, apply audio amp service
methods.

Not quite - it has flyback boost and tailored feedback for linearity.

Either of those can cause similar symptoms.

 

[Ian Field]

<mhooker32@gmail.com> wrote in message
news:c5b3309f-f414-4936-bd35-fc7cacbc7c60@googlegroups.com...

On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback
loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens.
i did change out every cap, and it was exactly the same. no better, no
worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image.
no better, no worse.

There might be a flyback diode lurking nearby - it could've gone leaky.

 

[Ian Field]

"John-Del" <ohger1s@gmail.com> wrote in message
news:514af99a-2f1b-41a7-8a6b-dc0dea0292ca@googlegroups.com...

On Thursday, July 6, 2017 at 11:18:38 AM UTC-4, mhoo...@gmail.com wrote:
On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com
wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson
wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback
loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I
didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what
happens. i did change out every cap, and it was exactly the same. no
better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the
image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt
supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that
this is
only 12 volts, maybe the diode?

--

Rick C


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good,
and look like brand new. no physical damage.

Not saying the yoke is the problem, but a single turn shorted to an
adjacent turn will not change the resistance reading on your dmm, but a
single shorted turn will totally collapse the magnetic field of the coil.

A ringer is the best instrument to check for shorted turns.

DSE did one, but I don't think the kit is available anymore.

The schematic is floating about and there's no unobtanium in the parts list.

 

[John-Del]

On Thursday, July 6, 2017 at 5:18:47 PM UTC-4, mhoo...@gmail.com wrote:

On Thursday, July 6, 2017 at 3:58:22 PM UTC-4, John-Del wrote:
On Thursday, July 6, 2017 at 11:18:38 AM UTC-4, mhoo...@gmail.com wrote:
On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the feedback loop that is failing, that can cause severe linearity issues.

G²


Granted, however the OP did say he recapped the monitor and I didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what happens. i did change out every cap, and it was exactly the same. no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that this is
only 12 volts, maybe the diode?

--

Rick C


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf

https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out good, and look like brand new. no physical damage.

Not saying the yoke is the problem, but a single turn shorted to an adjacent turn will not change the resistance reading on your dmm, but a single shorted turn will totally collapse the magnetic field of the coil.

A ringer is the best instrument to check for shorted turns.

not sure what a ringer is, but im pretty sure i dont have one. you mean like a tone generator, and you move it around the yoke ?

A dedicated instrument that checks inductors for shorted turns by injecting a waveform and counting the "rings" (like echos). A shorted coil won't ring or will ring very low. In the old days, several companies made "flyback" testers that would check flybacks and yokes for shorted turns. I have a Sencore LC75 that has a ringing feature and it works well.

Another way of checking the yoke out of the circuit can be done with a scope. If you can identify and electrically separate the two halves of the vertical yoke, you can connect each section to the calibration output jack of your scope and monitor the resulting waveform of each. Unless the top section shorted to the bottom, you can be pretty confident you have one good section and one bad. If the waveform on one of the sections is severely distorted compared to the other, it's a yoke issue. If both waveforms look the same, the yoke is most likely good.

 

[John Robertson]

On 2017/07/06 2:26 PM, Ian Field wrote:

"John-Del" <ohger1s@gmail.com> wrote in message
news:514af99a-2f1b-41a7-8a6b-dc0dea0292ca@googlegroups.com...
On Thursday, July 6, 2017 at 11:18:38 AM UTC-4, mhoo...@gmail.com wrote:
On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
mhooker32@gmail.com wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4, mhoo...@gmail.com
wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson
wrote:
On 2017/07/05 12:35 AM, stratus46@yahoo.com wrote:
And if it has a large value (1000-4700uF) cap inside the
feedback > >>>> loop that is failing, that can cause severe linearity
issues.

G²


Granted, however the OP did say he recapped the monitor and I
didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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its an IC, an LA7833( nte1773) . i'll change it out and see what
happens. i did change out every cap, and it was exactly the
same. no > >> better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the
image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt
supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that
this is
only 12 volts, maybe the diode?

--
Rick C


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_manual.pdf


https://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf


B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out
good, and look like brand new. no physical damage.

Not saying the yoke is the problem, but a single turn shorted to an
adjacent turn will not change the resistance reading on your dmm, but
a single shorted turn will totally collapse the magnetic field of the
coil.

A ringer is the best instrument to check for shorted turns.

DSE did one, but I don't think the kit is available anymore.

The schematic is floating about and there's no unobtanium in the parts
list.

The old DS ringer was designed by Bob Parker and was best for checking
flybacks (LOPTs), not much use on yokes I'm afraid. The kit is now made
by Anatek (we carry it on Flippers), but you would be better off with an
inductance meter - split the vertical windings and each side should be
identical.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."