LisaList2

Note to all: the neck of the CRT is fragile and easily broken by a bump or knock, and when broken, the CRT implodes resulting in flying shards of glass that will cause significant bodily injury. In addition, when power is applied, the high voltage of the CRT stinger can cause electrocution. Make sure you exercise appropriate caution, wear safety glasses and gloves, and have competent assistance nearby in case of an accident.

This thread started by mst3k on September 24, 2026

Greetings,

I have a non-working Clinton CRT.  Dead.  No flicker. No glow. Nothing.
I tried my broken CRT in two different Lisa's.  No go.  It was dead.

So, I ordered and got an 'untested' Atari SM124 monitor and swapped out the SM124 Goldstar CRT in one of my known good Lisa's.

No go.  The SM124 Goldstar tube was dead as a doornail, so I tried it in another Lisa and still no go.
So I put the Goldstar tube back into the Atari SM124 monitor and lo and behold I found a bent pin on the neck.
I fixed it, turned on the SM124 and the SM124 flickered to life.
Soooo, I pulled the Goldstar CRT from the SM124 and put it back into a working Lisa with the newly repaired pin.

No go.

Soooo, I pondered and thought to myself why does this Goldstar CRT work in the SM124 but not my Lisa.
The only thing that I could think of that I had not tested was the CRT yoke from the Lisa that had the 'bad' tube.
So, I tore apart one of the good Clinton tubes from a working Lisa, removed it's yoke and put that yoke on the Goldstar tube and put that into a known good Lisa.

The yoke was on me.  I started a yoke.  No yoke, I had yoke on my face.  etc.

The Lisa CRT that I 'assumed' was dead is fine.  The yoke is bad.

Of all the things I don't know about Lisa's, which is formidable, knowing how to troubleshoot a non-functioning CRT yoke is right up there on that long list.
I've read about broken windings causing interference, but I'm not even to the interference stage.
I have no idea where to start.
Has anyone 'fixed' a yoke before?  All I can come up with is that the connectors from the yolk to the video board are bad (but they 'look' fine).  No missing pieces or corrosion that I can see when I compare the 'bad' yoke to a 'good' yoke.  Those connectors look to be simply soldered to the yoke on the end of two short pieces of wire and removable so I guess I will start there.  Any other ideas?

I'm 'assuming' too that the Lisa Yoke Store shut down a long time ago and buying a 'new' yoke is out.

Quote from: mst3k on Yesterday at 06:14:40 PMI started a yoke.

Each of the vertical and horizontal windings should have continuity (resistance between the two pins is low).

Other than that... pictures from lots of angles perhaps? Although I guess only one picture is needed if it is from the correct angle.

Just to make sure I tried the yoke in question on a third Lisa with a known good CRT this morning with the same result.
The neck glows but no image. 
I hit the connectors with a bit of DeOxit as well.
I removed the neck clamp for the photos.
It might turn out that this is no yoke.


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I don't see any scars or signs of obvious physical damage, so that's hope inspiring.

Did you check the continuity? That might narrow down which winding you should be inspecting carefully.

Is it possible the connectors were not plugged-in correctly (swapped) on the Video Board?

The points where the coloured PVC insulated wires connect might be vulnerable to a manufacturing issue or flex / heat damage.

Using (a lot) more light for such pictures might get greater depth of field and so more of it in focus... (I'm not a picture expert).

I checked continuity and it seems fine.
The connections to the Video Board were/are correct.  A good thought but I've had lots of practice the last couple of days and I think I have that down.
I was wondering about the 'ring' adjusters.  Is there a way to position them so that there is no image?
I really have played with those at all and maybe should revisit them.  My thought was that they didn't effect the image, just the position, but I could (obviously) be wrong.

Quote from: mst3k on Today at 02:02:49 PMI really have played

I really HAVEN'T played with those...

Quote from: mst3k on Today at 02:02:49 PMI checked continuity and it seems fine.

Do you have any instruments that can measure further characteristics (other than resistance)?

QuoteI was wondering about the 'ring' adjusters.

In my very limited experience, they don't move the image far enough that you wouldn't see it (only a couple of cm at most), but since it doesn't work, I see no harm in marking their position and moving them about. As there is no blue tamper indicator securing the rings, I'd guess they have been moved already.

Note to all: the neck of the CRT is fragile and easily broken by a bump or knock, and when broken, the CRT implodes resulting in flying shards of glass that will cause significant bodily injury. In addition, when power is applied, the high voltage of the CRT stinger can cause electrocution. Make sure you exercise appropriate caution, wear safety glasses and gloves, and have competent assistance nearby in case of an accident.

When you power it up, do you see a dot in the middle of the screen as though the circuit is running but there is no deflection?

If not, then a thought, since you have a good yoke too, but I don't know if this will work, nor how dangerous it is, so try it at your own risk: You may be able to isolate the problem winding by eg. connecting the vertical of the good yoke and the horizontal of the bad one to see if that works, and vice-versa. I'd put the good yoke on the CRT so you'd see the horizontal or vertical line if the circuit is operating. Be super careful!

Quote from: mst3k on Today at 02:02:49 PMI checked continuity and it seems fine.

See if there is continuity between each of the windings eg. a pin at each connector and the ferrite core. If the magnet wire has been pressed against a sharp edge of the ferrite, it could cut through the insulating varnish, and since the ferrite is conductive, it may short-circuit the winding. Using a rounded tool that doesn't cut into the wire's insulation, you may be able to lift the wires away from the sharp edges to remove a short circuit.

Have you tried cleaning the contacts on these connectors (in the last photo)? Maybe there is some buildup and Deoxit is simply not enough?

(Aside:) I was interested to find from a thread on 68kmla that a broken yoke coil doesn't necessarily mean no picture: instead you can get something that looks quite interesting!

The conclusion I draw from that is that AC signals are for wizards. (Including some quite famous ones.)

I have found that the yoke connectors require an unsettling amount of pressure to be applied against the video board (which absolutely bends in the process) before snapping into their fully seated homes. You might even want to loosen the video board and safely stabilize it from the back while plugging those in.

Once upon a time, I didn't press hard enough and the connectors didn't seat properly, resulting in a lack of horizontal and vertical deflection, which quickly left a permanent scar dead center on the screen. Sigh...

Don't be me.