Pentranic 1432 display issues [RESOLVED]

[Arm123]

Just found D506 open...  Let us prey   

[Arm123]

Ok...   I just went over to where this beast was stored and fired it up, after replacing D506 (15df8) with a NTE577.  I finally got an image !

Here is the result...



As you can see the flyback 'screen' control and geometry pots need adjusting.  However, there appears to be a portion of the screen that is 'compressed' to one line.  The middle section of the screen is missing and compressed.

Im thinking this has something to do with vertical deflection ?  So i am going to check IC3 (an5521) and IC701 (LM1203N) for shorts and bad solder joints.

Anyone see anything like this before ?  Could it be a pot on the board that needs adjusting ?  Iv never seen a control on any chassis that had such an affect on the picture before.

The saga continues ....   

[Arm123]

Im wondering if i damaged IC3 (an5521) by trying to start the monitor to test it...   because D506 was open ?  I checked it for shorts but found none.  Maybe its just malfunctioning...

[gokun]

Well, congrats on making some progress first of all! I know first hand how frustrating this crap can get...somewhat like a dog chasing it's tail at times...while on fire...
anyhoo, I played with all my knobs on your behalf(now that sounded bad!) and I cannot get it to make that white line like you have so I'm guessing you're right and something else is amiss...
correct me if I'm wrong here(cause I probably am) but it kinda reminds me of vertical collapse(right term?)or rather the start of it...that's really the only time I've seen or heard of the line in the middle symptom...but bare in mind I'm still very new to all this so definately wait for grantspain and the others to chime in before you listen to me ...still I think you're on the right track, and the parts you mention are likely places to start, so don't give up and keep us informed! Good luck!
[EDIT]
as for the IC, I think it is possible to damage it like you mention...speaking personally, I am very very paranoid, so I would probably replace it just to be safe...after all, it couldn't possibly hurt.

[Arm123]

Thanks gokun.

It is a pain in the --I'm attempting to get by the auto-censor and should be beaten after I re-read the rules-- because this showcase cabinet is 50 miles from me.  So i can only take the chassis home and make mods, then go test every other weekend.       At least im closer than i was before, so i cant be too unhappy.

I am just wondering if this looks like bad case of 'fold over'  to anyone, or the start of vertical collaps ?

Just wanted to get some opinions.

[grantspain]

what voltage do you read on d506?
have you checked d399,401,407,r336,c393,326
could be the ic3

[Rickn]

Replace C318 it causes some real weird problems at times.

Rick N

[Arm123]

Grant and Rick...  thanks very much for your input.


Grants suggestions:

Even though i looked over those diodes before, I checked D399, D401, D407.  Then i checked C393,and C326.  All was well.  However, C510 (right next to C326) had a cold solder joint on one leg and pulled right out with little to no force.  So i touched that up.

I did find something interesting with R336 though.  On the schematic, its supposed to be 1W 4.3 ohms, but mine reads as 100 ohms. Is that odd ?

I could not take any voltages at D506, because the tube is not at this location, but i will tomorrow.



RickN's suggestions:

I pulled off that TAN C318 and gave it a look.  It looks brand new, and reads above spec. when tested.  Should i replace it anyway for good measure ?



Thanks again guys, im just trying to gather up a parts list here, because i have replaced so many things on the chassis and had to order out (mouser) for the parts.  So its getting pretty costly...

At this point the only toasted components that i have found are D506 and IC3 (an5521).  I may just replace IC3 again and test tomorrow.  Wish me luck   

[Arm123]

I changed C318 (TAN 2.2u 16v) and IC3.  Still the same image persists.  I started looking around at some other parts.

Found a couple of odd things while poking around....

C333 (330u 25v) failed, replaced it
C907 (4.7u 75v BP), in its place was a 10u 50v BP part
C392 (22u 50v), in its place was a 22u 25v part
R336 (1w 4.3ohm), in its place was a 1w 100ohm part

Does anyone find the above strange ?  After all, the schematic states different parts.  Should i change the parts back to the origonal stated by the schematic diagrams ?

[grantspain]

r336 should not be 100ohm-25" tube is a sort link,29" is 1ohm 2 watt,33" is 4.3ohm 1 watt
there are a few other tube size dependant components

[Arm123]

Yup...   this chassis is for a 33" tube.  I saw that R336 was dependant on tube size.  So i will be putting in the correct part value (4.3 ohm 1w).

Someone obviously went threw this chassis and make some wrong component substitutions.  So this will make fixing this thing that much harder.   

[grantspain]

yes thats always a danger,someone may have had a go at this before you-i have had similar problems over the years
follow the schems not whats on the chassis

[Rickn]

So before you go changing all those parts to what the schematic says... need to clarify. Did the noard work right at one point and then develop this problem?? That is without having anyone monkey around with changing parts- if so do not rush to change them.

I will be back in the shop tomorrow or Tuesday and try to find time to check a 32" board to verify what the values are.

If you do not hear from me by Wednesday, then e-mail me direct to remind me.

Rick@Niemandisplays.com

[Arm123]

Thanks Rick...

Since i have aquired this monitor, its never worked properly.  It did have a better image than this, before it totally failed.

Im just checking and making notes thus far.   So i wont actually change anything till i hear back from you.

[Rickn]

just checked the values of the components on a good board (never been changed0
Your board has the right values C333= 330u, C907= 4.7u, C392= 22u, R336=4.3 ohm.

When you changed c318, did you realize it is polarized and must be inserted correctly?? Also, you mentioned C333 had failed- check R401 and the check the 18 volt line to be sure it is 18 volts.

Good luck

Rick Nieman
Rick@niemandisplays.com

[Arm123]

Happy Monday Rick   

Actually, your saying that the schematic values are correct and the parts in my chassis are wrong (ie 336 has a 100 ohm, i will change it to 4.3 ohm).

I will also check R401 and TAN C318, im certain i installed it with the correct polarity.

Thanks for confirming.  I have actually made note of several parts that differ in value from the ones in the schematic.  Im going to post them here, just for fun, once im done adding the correct value parts.


Thanks for double checking.

[Arm123]

So far i found the following parts with the wrong values...  i corrected them.


R336 found 105ohm, replaced with 4.3 ohm
R369 found 1.6 ohm, replaced with 3.3 ohm 5 w
C907 found 10uf / 50v BP, replaced with 4.7u 75v BP
C392 found 22uf / 25v, replaced with 22uf / 50v

[grantspain]

does it work?

[Rickn]

Your board is right... the schematic is generic. All boards are subjcet to change by the manufacturer tomatch tube and yoke types.

Rick

[Arm123]

does it work?

Unfortunately, i cant test this until Saturday...  This blows   

Iv made notes, of what the previous values, of the components i replaced.  So, i can go back to the seemingly 'incorrect' values.

[Arm123]

I just pulled L501 and the outer plastic casing crumbled off and looks burnt.  This is probably what i smelled when the monitor initially failed.

Im not sure how to test this with my DMM...  any ideas ?

[Rickn]

Yeah, sounds like that could be part if not the whole problem. To measure it you will need an inductance meter. Probably dont have one... right.

Any chance you have an adjustable DC power supply... if so you can lift the coil and substitute the 18volts for 18 volts supplied by the flyback.

Richt now all the components on this line R401,D304,C333,L401,C402 are suspect.

RickN

[MonMotha]

I just pulled L501 and the outer plastic casing crumbled off and looks burnt.  This is probably what i smelled when the monitor initially failed.

Im not sure how to test this with my DMM...  any ideas ?

You can do a partial test by just using the resistance (ohms) setting.  After letting it settle for a few seconds, it should read something very low (usually less than 1 ohm, but sometimes up to 10 or more, depending on construction).  If it reads as an open, it's toast.  If it reads low ohms, that doesn't guarantee it's good, but if it reads as an open, then it's definitely broken.

[Arm123]

Rick, are you sure you dont mean L401 on the 18v line off the flyback ?  Cuz im looking at the schematic and dont see how L501 (my burnt part) connects with R401,D304,C333,L401,C402

In any case, thanks Rick.

I don't have an inductance meter, Iv never had an inductor part go bad on me before.  Ill have to buy one.

I was in the process of testing all the components on that line with L501.  Ill just replace L501 anyways and check the components you mentioned.

Your the best Rick..  thanks for being so patent with me  ;-)

[Arm123]

I just pulled L501 and the outer plastic casing crumbled off and looks burnt.  This is probably what i smelled when the monitor initially failed.

Im not sure how to test this with my DMM...  any ideas ?

You can do a partial test by just using the resistance (ohms) setting.  After letting it settle for a few seconds, it should read something very low (usually less than 1 ohm, but sometimes up to 10 or more, depending on construction).  If it reads as an open, it's toast.  If it reads low ohms, that doesn't guarantee it's good, but if it reads as an open, then it's definitely broken.

I checked the burnt part and let is sit for a couple minutes.  I get 0.00 ohm with no fluctuating...  Fried ?

[MonMotha]

0.00ohms is the expected ideal value for the resistance of an inductor.  It may still be bad (could have failed partially-completely shorted), but it could also be fine as a measurement of 0 ohms does not indiciate a failed or good inductor.

If you had measured an open (infinite ohms), then you would know it had failed from that test.  You'll need an inductance meter to test further.

[Arm123]

no worries...  ill just replace it for good measure.

[Arm123]

Checked all the parts on the same line of L501 and L401.  Everything seems to check out ok.

Im thinking its L501 thats burnt, because i get no fluctuating readings like a few other inductors iv tested (fluctuating from 0.0 ohm to 0.5 ohm).

Ill have to make my way down town to see if i can fetch these parts.

[Arm123]

"It works! Ha ha, it works! I finally invented something that works."
—Doc Brown


Well, I spent 7 long hours on this thing.  Finally got it working 

I started out by putting in the old parts that i replaced (HOT, RGB amp, FET, IC2 etc)...  to see what was actually initially at fault.   My initial replacements of IC3 and D506 were the only components that were causing the thing to not fire up.  However, after a couple minutes of running, the old HOT shorted.  So that was finally needing to be replaced.

Still the problem persisted, and i was out of ideas.

I decided to replace R336, with the same value fromthe reference schematic, and see what would happen.  To my suprise, i got rid of the 2 lines and the image was filling up the whole screen !  However, the chassis was screaming at me and i could not get it to sync horizontally.  It was almost there, but not all the way.  So i replaced R369 with the proper value, and all systems were a GO !

So i guess this turned out to be a hack job by someone else to account for the failing symptoms of a dying part ?  Who the hell knows.

I just want to say thanks to all that took the time to read this thread and suggest something.

Thanks to all   

[grantspain]

i am really glad you got this fixed,it has been an epic crusade
 

[Arm123]

i am really glad you got this fixed,it has been an epic crusade
 

Thanks very much for your help along the way Grant.

This has been my hardest fix ever !  I wanted to cop-out and send the thing over to RickN, but i resisted the urge.

I did buy an inductance meter, and tested those parts mentioned above.  They all checked out ok, even the burnt one.

Just for a summary of info, this is what ended up fixing the trouble....


Screen curl:
C516
C551
C313

Vertical collapse:
D506
IC3 (an5521)

Strange lines mid screen:
R336 found 105ohm, replaced with 4.3 ohm
R369 found 1.6 ohm, replaced with 3.3 ohm 5 w


The picture has a very small / fine wobble to it,  which you can barley see.  I think ill replace all those old IC's and the FET with new ones for good measure.

[gokun]

NICE!! Congrats!!

[Pinball Wizard]

Well I'm fighting the same chirp noise as you were. HOT checks out good, IC3 isn't shorted and neither is d506. What should I be looking for?