Pentranic 1432 display issues [RESOLVED]

[Arm123]

I recently purchased a Midway "Invasion: The Abductors" at an auction.  Installed in it was a Pentranic 1432 33" monitor.  It seems to have an issue i am trying to solve.  I have tried adjusting all the display controls in the cabinet.
 
There seems to be some kind of "tearing" at the top of the image...



Its as if some rows of pixels are missing.  I have tried moving the image around to different portions of the screen.  It results in the same tearing effect.  I am not concerned about the crappy positioning (my fault) of the bottom corners, it is fixable via the cabinet display controls.

I am wondering what my options are ?  Any suggestions are appreciated.

Thanks.

[grantspain]

when you say all the adjustments does that include the one's they like to hide on the main chassis

[Arm123]

when you say all the adjustments does that include the one's they like to hide on the main chassis

Yes indeed, I opened up the monitor housing and messed around with the controls that i can see.  I see controls for R, G, B, contrast, brightness and focus (which seems to blur and sharpen the image).

I cant locate the service manual for this baby...  and its pretty dusty inside.  I cant see any other controls in the chassis.  I’m going to clean it out and see if i can locate any other controls.

Any suggestions are appreciated.

[StephenH]

Here is the schematic:

http://www.alsmarketing.net/schematics.htm

[Ken Layton]

Contact Rick N at monitor manufacturer, Nieman Displays. He has experience with Pentranic monitors.

[Arm123]

Thanks alot for the responses guys.

Ill muck around with it this coming weekend.  See if i can sort it out.  If not, ill make an atempt to contact Rick N at Nieman.

Thanks again for the diagrams StephenH   

[rockin_rick]

My polo looks like that when horz freq is adjusted.  It goes from good/correct, to that, to horz blanking visible on screen, to garbage.  When it looks like that it is on the very edge of going bad.  FWIW

Good luck,
Rick

[meequalgreat]

yeah I had this same problem until I found my horizontal adjustment knob, which was on the chassis away from everything else.

[rockin_rick]

I'll just add that the h freq only effects the curl of the screen, not the missing top pixels.  I'd assume that your top line of pixels are missing due to another setting (perhaps v phase and/or v size?)

Rick

[Rickn]

Yes- the Horizontal hold to fix the curl a combination of Vert pos'n and VHold for the missing "Pixels' and if that does not do it there is a small Tantalum capacitor to change C318.

Good Luck

Rick Nieman
Rick@Niemandisplays.com

[Arm123]

Hey guys.  Thanks for the replies

I have spent the better part of a Sat. trying to get this thing to display a descent image.  I did, indeed, find two more controls buried in the monitor chassis.  One was a 'zoom' control and the other seemed to 'shrink and expand' the bottom portion of the screen.

The only way i can get the top part of the grid to display is to shrink the image to the 1/4 the size of the screen in the middle.  Once i try to expand that image, the top part of the grid seems to roll over behind the image.

After a spray of compressed air, I took a look inside the chassis to see if i can see any burnt or swollen caps.  I couldn’t see any.







After playing with the extra controls, i found in the chasis, this is the best image i could come up with (as far as the top of the grid is concerned).  No missing pixil rows anymore.  However, the image seems to bend over its self.



Iv played and played with the Vert pos'n and VHold.  Im guessing the only option is to replace that cap specified by Rickn ?

Any input is more than welcome.

[Rickn]

No- not a "Zoom" control, more likely B+ , the other control is vertical linearity,

Send me an e-mail to Rick@Niemandisplays.com

Copy/Paste this post in the e-mail to remind me - I will send you a service manual


Thanks again

Rick

Rick@niemandisplays.com

[Arm123]

Email sent...  thanks Rick 

[Arm123]

Hey guys...

Well, i haven’t touched this particular unit for a few months.  I just turned my attention to it today and powered it on.  I saw a horizontal line threw the middle of the screen...  the picture seemed to be ‘compressed’ to one line.  Then I smelled something burning, so I powered down and waited 10 min.  Powered back on and nothing...

I do hear a faint, short wine or buzz repeatedly and no picture or power on.

What, if anything, can I do about this ?  Any thoughts are welcome.

Thanks.

[Rickn]

Likely the Horizontal output transistor.

Check to see if it is shorted.

Good luck

Rick

[Arm123]

Thanks Rick.

I will locate, replace and pray 

[Arm123]

I checked the HOT and it wasn’t shorted...

I replaced it anyways.

Im still hearing a short repeated 'beep'...  more like a hummm, over and over.

Ill have to do some more investigating.

[qrz]

 a flat line is usually the loss of vertical deflection. occasionally, there may be a cold solder joint feeding the horiz yoke that will cause a flat VERT line . but,  this is VERY infrequent.
if the horiz output xistor fails , there will be NO high voltage and thus,  NO DISPLAY at all ..

the vert output IC may be "toast" and perhaps the supply res and diode on the 20-30v source.
screen pic does show some foldover , so there are caps that should be changed as well ....

qrz

[grantspain]

not your model BUT many machines in the u.k used pentranic monitors(i am sure its ch1450),there was a lovely design fault whereby the frame i/c had a crappy heat sink and after time it would develop bad solder joints and in turn start to overheat the smoothing cap which would then break down completely and then in the extreme would cook the diode
the symptoms would start with a frame foldover gradually progressing to a full frame collapse

[Arm123]

Hey guys..  thanks for the insight.

if the horiz output xistor fails , there will be NO high voltage and thus,  NO DISPLAY at all ..

Indeed, there is no display anymore.  But after changing the HOT i can assume its not that.  So i think im going to try to locate the vertical output IC and replace it.  See what the result is.

not your model BUT many machines in the u.k used pentranic monitors(i am sure its ch1450),there was a lovely design fault whereby the frame i/c had a crappy heat sink and after time it would develop bad solder joints and in turn start to overheat the smoothing cap which would then break down completely and then in the extreme would cook the diode
the symptoms would start with a frame foldover gradually progressing to a full frame collapse

Just a couple questions if you dont mind educating ---my bottom---   

For future reference....

Whats the "frame i/c" ?

And whats a "smoothing cap ?"



Thanks guys.

[grantspain]

us brits use different terms than our american cousins
frame i/c=vertical output i/c
although this is the same
smoothing cap=electrolitic capacitor acting as a voltage smoothing component on the frame(sorry vertical)i/c voltage input pin

[Arm123]

lol..  thanks mate.

I need to get the lingo down, so i can communicate with those who use a 'foreign tongue’ such as your self        J/K

I was pretty sure of the first one, because of a similar term 'frame buffer' that I do know.

The last one, I was clueless and wanted to confirm.

Thanks again.  Ill keep plugging away at this puppy until something positive happens.

Ill keep you all posted.

[Arm123]

Ok, I got around to looking at this thing.  Being summer and all, I want it fixed.

I went threw the board, found a bad solder joint on one of the coils near the PS section.  Re-flowed that, and started testing the caps.  Checked C516 start up cap as well as C551 and c313.  All seem to check out except the large startup caps (100uf 200v) they were leaking heavily, down to less that 20uf (probably what was causing the folding?).  I replaced them.

Then I checked Fet Q501 and start-up resistor R510.  The resistor is fine.  However, the Fet seems to only read on 1 of the 6 diode test combinations (should be 2 readings).  Which leads me to believe that its bad.  I have also tested for continuity, and get none in any combination.

I can’t seem to find a replacement for it.  Looked threw a dozen local shops to no avail.

I also replaced the HOT and an5521 frame IC for good measure.  Would you guys bother to fire this up with out replacing that Fet ?

[Arm123]

Just did some continuity comparisons with the old and new an5521.  The old one is indeed toasted, so that makes me feel a bit better.

I’m just concerned about the Fet possibly being bad.  Any second opinions ?

[grantspain]

i was kinda expecting IC2 HA11235 and a few of the caps nearby to be the culprit in your case

personally i do not think the FET will be faulty,unless you really screwed the B+ right up-still doubt it though

[Arm123]

Hmm.. 

I know that an5521 was bad because i found a short on pins 1 and 2.  None on the replacments.

IC2 ill have to see if i can find a replacment HA11235 to at least compare it with.  Ill also check thise caps around it.

About the Fet...  I cant seem to find a replacment.  I just did a standard transistor / diode test on it and only got 1 positive result out of 6 test combiations.  There 'should' be 2 positive results.  Do you think its bad ?

[grantspain]

i can call pentranic to find an equivilant
i am pretty sure you will get a diode reading from source to drain only

[Arm123]

Thanks Grant, makes me feel better.  Ill try and fire this thing up.

I cross referenced that 2SK1507 to 2SK2645 or NTE2989, just incase anyone wants to know.

[Arm123]

Well...  I tried to fire up my Pentranic after make my mods and it didn’t work     Still, same chirping.

I put my ear to the chassis and the chirping seems to be coming from the top right of the board.  Where the FET and sub power board are located.

Since i still have not replaced the FET transistor, i think ill do that and check on a few other components in that area.

[grantspain]

just helped a chap with a 988 chassis and was getting a similar problem,when you swapped out the horizontal output transistor(if it had a metal back) did you refit the insulator sheet

[Arm123]

Hey there Grant.

The original HOT did indeed have a metal back.  However, the equivalent replacement did not.

Still, i used the insulator backing...  Same issue with both HOT's.

Im actually convinced that the original HOT is still good / working.

[grantspain]

i still think its something to do with ic2

[Arm123]

yup, ill change it and the surrounding caps...  Just didnt have the parts on hand, so i left it for last.

[gokun]

Hey man I just fixed mine!
take a look at my post about the last batch of stuff I replaced and see if it helps you...
I never did replace those 2 resistors I mentioned might be causing the no power deal btw....they were fine.
Also I found an exact match for my FET if you need a 1507 I have 2 spares. Anyway, good luck and I will continue to follow your thread and try to help where I can.  Good luck!

[gokun]

Just curious if you had any luck with this yet?

[Arm123]

Just pulled the trigger on the parts i needed...  IC2 and the FET, waiting for delivery.

Ill make sure to update with my progress, or lack there of  ;-)

[Arm123]

Replaced the Fet and IC2.  I checked both of the 'pulled' parts for shorts and they came up clean.  So im not optimistic, that they were bad...

I also checked D502 and it turned up as working.

Just for the hell of it, i replaced Q302.

I really hope this works   

[gokun]

Hope springs eternal-Let us know how it turns out!

[Arm123]

Tried it yesterday and its still chirping.

I'm sad, but i guess i must keep searching for the culprit.

I may have to send this one off the Rick N

[gokun]

well crap in a hat....are you sure the flyback isn't blown out? or maybe some part on the subpower board? just thinking out loud....subpower board being bad can cause lotsa crappy problems...and continually cause components to blow out(I learned that one the hard way0_o)