SE/30 - CRT Ghosting / bleeding to the right

[smiba]

Thanks!

I already made sure its not the CRT board, I've swapped that out and the issue persisted. The same board works fine on a different CRT (See my above post, I use the same CRT Board)

The only thing I've not tried replacing is the yoke, everything else has been swapped at some point.

Basically a different CRT with same internals does not show this issue (Same PCB Board too). Its only on this specific tube (and maybe the yoke, as that is the only "somewhat" removable part I haven't changed)

 

[LaPorta]

3.9 µf non-polar films are stocked by Mouser...I think EU shipping is prohibitive, though.

 

[smiba]

3.9 µf non-polar films are stocked by Mouser...I think EU shipping is prohibitive, though.

Shipping on Mouser kills me at the moment though (€20 for a €0.50 part)

The cap is unlikely to be a problem at this moment though, as a replacement tube doesn't show this issue.

 

[techknight]

I am having a super duper difficult time following along here. Maybe its a language barrier, maybe its me. I dont know. 

So, This ghosting issue. What have you tried? What have you swapped? Has anything worked? 

I just read your post above, and swapping the CRT tube itself makes it go away? If thats the case, then its a bad CRT. 

 

[smiba]

I am having a super duper difficult time following along here. Maybe its a language barrier, maybe its me. I dont know. 

So, This ghosting issue. What have you tried? What have you swapped? Has anything worked? 

I just read your post above, and swapping the CRT tube itself makes it go away? If thats the case, then its a bad CRT. 

Right now I swapped the CRT and that fixed the issue.

This brings us to the following conclusions:

- The Motherboard, analog board and power supply are most likely fine

- The CRT Board (which attaches to the back of the tube) is most likely fine
 

And leaves us with the following possible problem causes:

- The yoke is bad (wiring) on the CRT

- The yoke cable is bad to the yoke of the CRT

- The filament inside of the CRT is dirty

- There is another unspecified issue with the electron gun of the CRT

- There is an issue with my motherboard, analog board or power supply that the failing CRT is only susceptible to

So my plan is:

1. Check the resistance of the yoke wiring and compare it to a working CRT to verify there are no weird issues with the yoke

    (Preferably I would also be able to check the inductance of the yoke, but I have no testing devices for this)

2. Clean the filament by using a CRT rejuvenator

3. Give up and sell the CRT for cheap to whoever can live with the bleeding -- If no one buys it I'll just keep it myself as a testing part

Basically I'm on my last resort to get this CRT back to working normally. I hope the yoke is fine as replacing that is an absolute bitch. Preferably a CRT rejuvenator would just do the trick as that is relatively easy

 

[techknight]

Easiest thing to do is swap the yokes between the CRTs

you could have a bad wnding in the horizontal side of the yoke, but thats super rare. 

Otherwise, its simply a bad CRT. could be gassy, could have a short in the electron gun somewhere, Could have weak emissions, could be anything. Once the CRT itself goes bad, there isnt a whole lot you can do except replace it. Or try a tube tester and check it, possibly rejuvinate it. But keep in mind rejuvination is VERY temporary and it wont last. 

 

[max1zzz]

Shipping on Mouser kills me at the moment though (€20 for a €0.50 part)

The cap is unlikely to be a problem at this moment though, as a replacement tube doesn't show this issue.

Mouser (And digikey too) offer free shipping over a particular amount (£33 for the UK) so I would wait until your next recap job and then order all the parts from there, this is what I did recently when I needed a couple of crystals I could only get from the states that cost about £0.50 each, I added all the caps for the logicboards and PSU's of a couple of LC's to the order, Even though I could get those part's locally it was cheaper to add them all to the digikey order and get the free shipping

 

[PotatoFi]

Hey @LaPorta, this is the exact issue that I am facing on my Classic II that I am trying to source a replacement tube for. I wonder if I don't actually have a bad tube, but just a bad yoke?

Only one way to find out, I suppose. 

Right now, my Classic II just lives on a shelf in my office, where I turn it on to run Flying Toasters in the background of webinars and training videos. I figure that if the tube is not great, I'm okay with stacking up an hour or two a day on it. I get lots of comments - one attendee on a training last week urged me to pull the battery out and recap it ASAP!   

 

[smiba]

I just received the CRT rejuvenator, I plan on cleaning it up first and recapping where needed.

I don't have the right connector for the tube yet too, gonna have to work on that or convert one of the adapters I received with it (But preferably I would just find the right adapter)

Hope to give an update in a few weeks

@PotatoFi If you end up swapping the yoke please let me know if this affected or solved the issue in any way ^_^

 

[PotatoFi]

@PotatoFi If you end up swapping the yoke please let me know if this affected or solved the issue in any way ^_^

I will! I have poor @LaPorta in limbo right now, as I can't decide whether to buy his CRT or not. Very curious to hear how the CRT rejuvenator goes. Where the heck did you find that, anyway?!

 

[techknight]

Bear in mind Rejuvination is only TEMPORARY. 

It does not last. Rejuv was designed in the technician era to "get a customer by" until a replacement CRT could be ordered and shipped in. 

 

[smiba]

Bear in mind Rejuvination is only TEMPORARY. 

It does not last. Rejuv was designed in the technician era to "get a customer by" until a replacement CRT could be ordered and shipped in. 

This is a common misconception and it totally depends on what kind of failure the CRT is experiencing.

Yes, Rejuvination is not something that can be used to make a CRT last a lifetime.
Once the filament degrades far enough there is just not enough emissions to show a bright picture!

However it is possible there is a containment inside of the tube, causing trouble. By rejuvenating you will send a pulse through the filament, hopefully displacing whatever is causing trouble.

As my issue with the CRT isn't emissions, the picture is bright, I hope there is something that gives trouble with the electron gun. If my rejuvenator works, there is no reason to assume this tube will die again soon.

 

[techknight]

This is a common misconception and it totally depends on what kind of failure the CRT is experiencing.

Yes, Rejuvination is not something that can be used to make a CRT last a lifetime.
Once the filament degrades far enough there is just not enough emissions to show a bright picture!

However it is possible there is a containment inside of the tube, causing trouble. By rejuvenating you will send a pulse through the filament, hopefully displacing whatever is causing trouble.

As my issue with the CRT isn't emissions, the picture is bright, I hope there is something that gives trouble with the electron gun. If my rejuvenator works, there is no reason to assume this tube will die again soon.

LOL misconception.... Lets try this again. 

Any time you "rejuvenate" a tube, you blow off cathode material. That is how that works. When you do this, you drastically reduce the life of the tube. If the tube is already dead, Then it doesnt matter, and you can help prolong the life a bit. But that life, is short.  

This is different than contamination. However, the effect is still the same. it blows off some cathode material in the process. YOU DO NOT EVER send a pulse through the filament! This will usually result into an H-K short at the minimum, or worse, open the filament entirely. 

Now Shorts restore is different. This blows out any potential debris between the elements in the electron gun, and is usually safe unless you blow the lead off the element which is rare. 

There is a restore function which is less deadly, and could help. But rejuvenate is a last resort and if its bad enough to require that, it wont last. 

 

[LaPorta]

Is there any way that a specialized company can ever rebuild these things?

 

[LaPorta]

Hey @LaPorta, this is the exact issue that I am facing on my Classic II that I am trying to source a replacement tube for. I wonder if I don't actually have a bad tube, but just a bad yoke?

If you need a new one, I can always sell you that.

 

[PotatoFi]

Is there any way that a specialized company can ever rebuild these things?

I don't think so. There is a guy in the Eastern US who buys "glass" (tubes) and resells it. I watched a YouTube video interview with him and Bob from RetroRGB, and basically, he said that manufacturing is completely shut down. Additionally, all of the people who know how to do it are retired/retiring, so we're losing an entire industry. And that's just the glass... there's also flyback transformers, yokes... all of that stuff.

 

[techknight]

Last company in the US that rebuilt CRTs was Hawkeye. Their equipment was purchased by VTF and they chose not to pursue. 

Last rebuilder globally was RACS in France, and they are also gone. 

All CRT plants have also shut down. There may have been one or two in India, and I think they are gone now too. 

 

[LaPorta]

Perhaps to be lost to the dustbin of history...

I at least hope the information on how to make them survives.