SE/30 - CRT Ghosting / bleeding to the right

[smiba]

Hey everyone,

I've recently bought a troubled Macintosh SE/30 for way too much money.
(Issues with HDD, FDD, motherboard with extremely leaky battery and now also the CRT lol....)

I'm still working on some of the issues and waiting on replacement capacitors, the ugliest ones have been replaced but with the audio being extremely faint too I think all of them are in dire need.

Anyways, I'm making this topic to get some feedback on how to resolve this issue with the CRT. The image seems to "ghost" or affect the image to the right, its not extremely heavy but its enough to kinda bother me.

The alignment and geometry of it is mint, extremely pleasing to look at.

It looks like this:



Not sure if this is related, but pressing the reset button very clearly shows the horizontal sync collapsing, resulting in a "lightning strike"



Analog board looks good from a glance, but I haven't removed it as the internet made me really afraid to work on high voltage stuff like CRTs

 

[PotatoFi]

My Classic II, which is fully recapped, does the same thing. I haven't been able to figure out why.

 

[smiba]

My Classic II, which is fully recapped, does the same thing. I haven't been able to figure out why.

Both analog board and mainboard?

I'm finishing the recap of the mainboard on this mac tonight hopefully and I'll see if that resolves anything. I'll also be checking the video lines for any cracks and verify that any resistors or capacitors on its path are functioning.
Especially R20/R21/R22 and C40 on the Composite video path would be of interest to me

Will update you after I'm done

 

[blindowl]

I have one display with the same ghosting issue. I swapped in another display and it was fine with same analoge board/logic board etc. I think it’s the CRT itself. 

 

[Bolle]

Did you keep the CRT neck board of the old CRT or did one come with your replacement CRT?

I would have suspected it could be the CRT board could be at fault here as well...

 

[blindowl]

Did you keep the CRT neck board of the old CRT or did one come with your replacement CRT?

I would have suspected it could be the CRT board could be at fault here as well...

That’s what I’m trying to remember... I think I used the same neck board for the swapped CRT, but I could be wrong. 

 

[techknight]

yea only time I see faults like this is if there is reflections in the video wire, or a bad ground. Think craptastic VGA cables. 

 

[smiba]

Did a full recap of the board, this resolved audio issues and reset problems but sadly the ghosting is still there.

I think the analog board is in need of repairs yeah

I calibrated the brightness / cut-off, but on a cold boot it is way too bright (so bright that on its lowest setting there still is a visible picture on screen). If I wait 10 minutes its much darker and at 25% "brightness" the screen doesn't show a picture any more.

So this changes a LOT depending on temperature / run time

I'll check which parts to buy, preferably I'd replace all non-ceramic caps and preventively replace some of the parts on the video signal path.

Any resources for this? Bonus points if it also talks about optional replacements like certain diodes or fets, while I have it out I may as well

 

[smiba]

Found some information about the caps used on the analog board over here: https://wiki.preterhuman.net/Macintosh_SE/30#Replacement_capacitors_.28analog_board_.26_PSU.29

No sizes and such though, I'll measure it myself and update it.

Here is a pic of the mainboard recap I posted ealier about because I think it went pretty well, hope the analog board won't be too hard

 

[smiba]

As there is no way for my to edit the wiki unless I "request" an account, I'll just post the details here:


Analog board 820-0206-C


1 x 4700uf 16v - lead spacing 7.5mm - diameter 18mm

1 x 1000uf 16v - lead spacing 7.5mm - diameter 16mm

1 x 3.9uf 35v bipolar - lead spacing 7.5mm - diameter 16mm -- I have not found a in stock replacement for this. Looking for film capacitors but Farnell is fully out of stock

4 x 100uf 25v - lead spacing 5mm - diameter 8mm

2 x 220uf 16v - lead spacing 5mm - diameter 10mm

1 x 10uf 160v - lead spacing 5mm  - diameter 10mm

1 x 33uf 16v axial - length 13mm  -- Will replace with radial
1 x 22uf 50v axial - length 15mm -- Will replace with radial

I checked the CRT board's resistors and they all came back within 5% of their specification, so no problem there either. Joints look excellent on both analog board and CRT board.

Diodes on CRT and analog board behave as expected (as far as I can measure in circuit)

 

[smiba]

Sadly recapping the Analog board didn't show any results, horizontal image still collapses weirdly on reset and there still is bleeding/ghosting to the right.

All caps (Samyoung branded) measured reasonably within spec (all capacitance values are met higher then spec, ESR was a bit up but nothing that shocked me...)

I'm considering replacing the 3.9/35v bipolar with 2 regular polarized capacitors to make a bipolar (using 2x 10uF). This capacitor goes to the horizontal signal on the yoke, but I don't think its responsible for the ghosting/bleeding.

Also using 2x 10uF would make it 5uF, which is about 22% higher then it should... Might pull it too far out of spec(?)

I'm also considering swapping the CRT board with one of another Macintosh SE I'm working on at the moment, I don't know if it works as I'm still working on its mainboard that has been absolutely destroyed. But as its currently not populated it can miss it
(Also its already open, so its an easy swap. More on that mac over at my twitter: https://twitter.com/PurpleDug_/status/1300529486962864131)

To be continued... If anyone has any ideas let me know

 

[smiba]

CRT board swap did not resolve the issue or chance the behaviour in any way...

So its either on the motherboard, some other part on the analog board (resistor, ic, etc.) or the tube itself (which feels unlikely, as I don't understand why the electron gun would act this way)

 

[archer174]

Have you tried some contact cleaner on the crt pins? 

 

[smiba]

Have you tried some contact cleaner on the crt pins? 

I'm reluctant to do so as the contacts themselves look good and nothing happens if I move it around.

Also this behaviour is quite unlikely from a bad connection on the data line on the CRT or CRT board

 

[techknight]

You are going to have to continue playing the borrow/swap game until you can narrow down where the fault is. Its either in the CRT or analog board at this point. 

it could be a chip on the analog board, could be the CRT itself. 

 

[smiba]

CRT swap didn't have the issue, so its either the CRT itself or the cables to it...
Can anyone explain this behaviour of the CRT? I don't understand how the tube itself can cause this to happen

I'll need to fix this CRT I have in it now though, as it has its molex connector killed...

 

[techknight]

you can remove the yoke. and swap the bare CRT. 

Try another CRT and rule it out. Otherwise, you may need to borrow another analog board and try it. 

Also that burned connector could very well be causing your problem. Since its the horizontal winding that burns. 

 

[smiba]

The burned connector (Although it mostly just looks brittle?) is on the CRT that actually functions correctly... haha

The calibration on both screens is really well done, so I'd rather not remove the yoke (at this point). I think I have another SE that has horrible calibration so I might steal that Yoke as it would've been needed to be calibrated either way.

Is there any instruction on how to remove it? Its a fairly sensitive part so I don't want to break anything

 

[aeberbach]

I acquired a SE/30 a few months ago. Until this week I had not disconnected the yoke but I should have. The only things that haven't been working are focus (not as good as it should be) and the front brightness knob does nothing.

On cutting away the glue and removing the yoke I found a wire soldered from one CRT pin to the same pin on the yoke socket. Why would you do that unless the socket itself was bad? Sure enough, on cutting away the plastic mushrooms that hold the central plastic disk on that socket I found that one connector had broken inside. I fixed that, squeezed each socket contact a little tighter and replaced all. Right now it's all disassembled after epoxying back together but I'm hopeful, that wire had a real about-to-break feel about it.

It's worth a look at that socket to see if everything is actually connected with low impedance. Also well worth a look behind the plastic sheet at the solder connections of the socket to the small PCB - three of mine were cracked from flexing with one actually open circuit.