Analog board Classic II horizontal line

[dochilli]

I have an analog board of a Classic II that shows a single horizontal line on the screen. I replaced the TEA2037A but that did not change anything. With another analog board, the Mac works. What else can influence the vertical deflection?

 

[bibilit]

What are the output voltages ?

You should have a steady 5 and 12 volts.

 

[dochilli]

The volts are ok, 5,0, 12,0 and -11,8 V can be measured at the floppy disk port. The mainboard chimes but I get a bright horizontal line.

 

[bibilit]

Any picture ?

Can be a loose solder joint.

 

[Dog Cow]

I have an analog board of a Classic II that shows a single horizontal line on the screen. I replaced the TEA2037A but that did not change anything. With another analog board, the Mac works. What else can influence the vertical deflection?

That could be failing capacitors. I have a Classic whose screen display has been steadily degenerating for the past 2 years, and I powered it on last week to see it has now collapsed down to a horizontal line.

What I did last week was to disconnect the board on the neck to save the CRT phosphor. I then powered on the Classic and left it on for over an hour. Probably close to 2 hours. Then I powered off, reconnected the CRT board, then powered on. I now had a workable screen display that was only somewhat squashed. Another hour on and the screen image was expanded to almost normal dimensions with little distortion.

 

[dochilli]

I resoldered the usual points. Next I will try Dog Cows idea.

 

[techknight]

if you wanna get down to the bottom of it, youre going to need an oscilloscope and you will have to probe the vertical circuitry until you figure out where it is dying off. 

 

[Dog Cow]

Also what about sound? On my Mac Classic that I described above, the speaker is now very very faint, even at top volume. I have to put my ear to the case to hear the Wild Eep.

 

[dochilli]

1. I left the classic on with disconnected neck board for two hours and nothing changed. I had again the thin line.

2. I recapped the board, no change.

3. I resoldered LL2, PF1, PF2, BD1 and all cables to the neck board. No change.

4. I resoldered the neck board. No change.

Sound is ok. The mac chimes, when it is powered.

Has anybody schematics of the vertical deflection? I only found schematics for the horizontal deflection.

 

[mjhagen]

@dochillidid you end up fixing this?

 

[dochilli]

Not yet. I changed the analog board and the Screen against one of a Classic. Then it worked. The problem must be the analog board.