Color Classic analog recap

[falen5]

Took down my color classic last week, to be a kid for the day (again). 

I have 2 color classics. This one, all standard and the second one is the mystic that I did the video mod on.

all was ok for a while, then the display started jumping,twitching so decided to have a look. 

Opened her up, took out analog board, and found overheated components.

I replaced 9 caps around video circuit where the high temps seemed apparent. 2 of the caps had failed according to my tester and the rest seemed to be in spec. I replaced them with higher voltage caps

Video working again.

However , no matter what adjustments i make on the video control pots I looks like the red and blue are slightly 'shifted' (im not sure how to even describe it)

The logic board was recapped last year.

I have not replaced all of the caps on the analog board as i dont have them, only the ones where the burning took place.

The caps I dont have replacements for, I removed and tested them. Their values are in spec. But as some of these caps run very hot I am wondering if the values of old caps can go out of spec when they heat up.

The only true fix is to replace every cap, but theres about 50 caps on it.

There are also 2 diodes that look very crispy but according to the meter they work. The high temps had damaged the traces on the back of the board but I managed to repair that damage as well. Also , 2 resistor were very crispy. I replaced them with 2 watt resistors.

I am no hardware engineer but from googleing it seems that this overheating happens on all color classics. This is poor design , right?  Thinking of mounting a small 12 volt fan close to this area to help it stay cool.

Anyone have this problem with the red green and blue being 'shifted' out of position.

 

[mraroid]

Is this the standard Color Classic you are having issues with, or the one with the video mod?

mraroid

 

[falen5]

its the standard color classic maraoid.

All the soldering on the traces in the last picture was because the heat had lifted many traces. I used the solder to try to 'anchor' the components to something

 

[falen5]

I forgot to add , the misalignment of the red and blue only occurs in the top half of the screen , the bottom half seems to be fine. 

Could it be any of the 'lever' adjusters on the back of the tube itself?

 

[jhorvath911]

I remember a couple other threads here in the past with people having a purple tint on color classic screens, but I don't remember what they ever found out.

 

[techknight]

On the CRT neck board, the PCB that plugs into the rear, there is an H-STAT control. Adjust that and it will bring the convergence back into place. If it appears to have no effect, the pot is likely open, my first analog board had an open pot so I had to find another analog board

Otherwise, your convergence adjustment rings on the rear of the yoke could have been bumped as well. There is usually a dribble of glue that runs down the rings to seat them into place, and it can crack loose. Check that, and make sure that glue line is in alignment. 

Then your still missing a color, so youll have to play with drive pots and try to get that back. 

 

[falen5]

Thanks for all the info folks.

Techknight the adjusters at the back of the yoke are all in their original position. The glue mark is in tact. I tried adjusting 1 of those a bit, saw no differnce so I put it back. Will have a look at the h-stat. Already had it open looking for capacitors and leaks but didnt adjust anything. All the pots at the back of the analog board do their jobs. I get a nice, rectangular sharp screen. Its just this 'convergence' issue. I will give it a go and report back.

Big Thanks

 

[techknight]

if the convergence rings dont have any affect (They do, but it takes them all in tandem and its minor), Then you need to adjust the horizontal static convergence which again is a pot on the CRT neck board itself. big white one. Inspect the solder there as well. 

 

[falen5]

Techknight

You were 100%  right yet again.

H-Stat pot. Just a tiny turn and it all lined up perfectly. Makes me so happy. I thought I did something wrong somewhere, with all the bad traces and blobs of solder on the back of the board but now it looks like I did a good job, well it works anyway.

I have a perfect display.

I dont know why the pictures have a red look to them. I have adjusted the colors any they look perfect to my eyes. The white is white but in the photos they have a red tint. weird!

I thought I would have to desolder the silver caseing to get to the pot, but spotted a tiny hole in the pcb so it can be adjusted from the back while the h-stat is in situ.

ah jesus man, you made my night. bloody hours trying to fix this. I even opened the sheilding on the video amplifier part, removed and tested all the caps, they all checked out ok. no room for error with the soldering iron in there!.  I would never have found that pot.

again thanks man. that little turn of the screwdriver and to see the screen coming perfect is what its all about. Perfect display

 

[falen5]

few pics of finished repair. It aint pretty !!

on the board i changed 12 caps, most of the ones in pic a.

Found 2 of them to be dead on the tester

changed 2 resistors 

RF11 - Orange, White, Brown, Gold - 390 Ohm, 5% Tolerance (Measured 390 Ohm)
RL62 - Yellow, Violet, Black, Gold - 47 Ohm, 5% Tolerance (Measured 47.5 Ohm)

last pic is the pot to adjust for convergence problems - that little white guy next to my finger.  Techknight does it again

Thanks for all the help people. I wouldnt have a hope of fixing anything without ye.

PEACE from Ireland

im off to me laba!

 

[Bolle]

You are totally missing green on that display. Can´t just be the pictures.

Missing color is usually cold solder joints on the wires between neck board and analog board, drive pots on the analog board or a bad connection on the harness connector.

It was none of the above in my case though. After ruling all those out I found out that the grounding tabs on the logicboard did not make good contact to the metal shield in the bottom of the case.

Seems like video signals get messed up when you do not get proper ground as after bending the metal shield back in place and also popping up the metal tabs on the board a bit everything came back to normal.

 

[falen5]

trust me bolle it is the camera.

All the pots work including the green. If I turn up the green anymore the display is green to the eye

Before techknights but of magic i spent hours adjusting the pots. They all work

Although i will have a look again as I have the daylight now. My eyes are not good but they can be that bad!!.