IBM 5110 CRT Exploration (is it dead?)

[voidstar78]

For the IBM 5100/5110 there are two "styles" of CRTs. The MIM describes them as "with horizontal linearity sleeve" or without (PDF page 51, or 2-33 / 247).

I have a 5110 with tthe "horizontal linearity sleeve" style (which has more differences than just the sleeve part) - it happens to be a 1978 build of a 5110, but I'm not sure if that style of CRT is really older relative the other style or not. (I have another 5110 with that other style, which is working fine - I think both styles were used across production of both 5100 and 5110's).

Since this CRT isn't working, I'm taking it out and sharing a little bit about what the "other side" looks like. And I think this CRT is quite dead, but maybe someone has some suggestions on things to try.

Just 3 screws removes the CRT. I leave the 4th one attached to the ground wire (but it is detached from the CRT itself, and the ground is between the main system power input and the bracket used for the audio speaker). In other words, aside from the 10 small connector wires on the side, the CRT is standalone.





Here is why I think this CRT is dead... There is quite a bit of "bruising" around the edge of the display, along with the "shotgun scatter" around the center that I've seen on several other 5110's. These "bruises" aren't shadows from taking the photo, but dark spots within the CRT glass itself. Then beyond that, when powering on, nothing appears on the CRT - no change in hue or intensity, nothing to indicate that anything is trying to be drawn on the glass at all (and I tried adjusting the brightness and vert/horz sync).





And here's the "rarely seen" bottom of the CRT. On the right is the only connector, which is blue and reminds me of the Commodore-style connectors. This one has 10-pins.



Per the MIM, those pins are as follows: (I assume the same pins for either style of CRT) I verified I had about 0.8V on the Brightness pin, and did have +12V on pin 7 -- so this CRT was getting power.




The sticker on this particular CRT reads
GTE Sylvania CRT
type 5ST6111A
part no. 1-014-0716
CODE 2-739

It is also labeled as Ball Brother Research Corporation model "TV-5". Also labeled as IBM part number 1608865 EC832674.





And here is also why I won't spend too much time trying to "save" this CRT: the center piece (the red wounds of wire) is completely loose, it spins fairly freely, and there are gaps between the bottom and top. I don't know too much about CRT, but seems there are magnets and a vacuum involved, and none of that is secured in place here. Plus notice the "suction cup" piece (top left) has had some substance oozed out. However, the PCB looks OK (no apparent burn marks anywhere). I'm not sure if those are original caps, but it seems the original clips are in place that secure the PCB to the bracket (you'd have to cut those clips to get it off - you can see one of them in the bottom right of the image below - unless maybe those are replaced clips already?).

NOTE: The MIM does talk about if the display is tilted, rotating the entire "yoke" (but involves breaking some seals and re-gluing things). So maybe the "loose-ness" of this piece is normal, or that was attempted in its past. But just checking that the 12V was getting into the PCB (which it is), that's about as far as I'm comfortable troubleshooting on this CRT :D




Note that the IBM 5100/5110 have an external BNC connector, and that is still working on this unit. So with that, I don't really need this working CRT, I can use the system with the external monitor. I've also found small 5" flat screens with BNC inputs, I've thought I could remove this CRT, and substitute in a modern 5" panel (then routing that BNC cable internally).

 

[snuci]

You might want to see if you can find a 5" CRT on eBay. I bought two of them back in 2016. These were new 5" monitors that were entitled "Chuomusen 5" CRT Display QB0506 IBM 4592968". These had an IBM part number. I don't know what else IBM used these for but they were good enough.

Here is the new and old one. I believe I reused the original cage for fitment and originally restored look so it looked stock with new internals.


It was a while back but my screen had severe burn in and I replaced it. I bought two so I would have a spare and I would still like to keep it if possible. I literally opened the sealed box right now to take this picture.

The analog boards are not identical but the connectors line up and the monitor works. You may be able to find one if you look around.


I don't recall which version of the monitor this was but YMMV.

Good luck with the replacement.

 

[voidstar78]

Thanks, I'll keep a lookout!

I've confirmed the Eyoyo small LCD screens with BNC connectors also work. I think normally used in automotive or security systems. They also have built in VGA and HDMI, so versatile as a display for various things, and don't have to drag around an extra BNC/VGA adapter.

The size is ok, but there isn't much for OSD settings to better center the screen. And available in 7" size. This CRT was in a "spare" 5110 that is pretty beat up for other reasons, but the internals work - I've been thinking of swapping all the guts into a custom acrylic case. I grabbed a bunch of clear acrylic 1/4" thick sheets from JCP when they were going out of business. But I need a cut over 20"x20" which most consumer CNC machines don't support.

EDIT: also confirmed that the CRT doesn't have to actually be connected in order to boot up (to the Language ROS).

 

[voidstar78]

For reference (GTE Sylvania)

 

[Hugo Holden]

Panasonic made an excellent range of 5" VDU's ( have the schematics for these including the turn off spot killer modification that prevents the kind of phosphor damage you have seen centrally) unlike the VDU here, they normally come as open frame, without the external shield, and both green and white phosphor tubes were available for them, the green are still available I think:

HP Agilent 8920A Communications Panasonic LP0619EVC-REV 1 CRT Display DC | eBay

Find many great new & used options and get the best deals for HP Agilent 8920A Communications Panasonic LP0619EVC-REV 1 CRT Display DC at the best online prices at eBay! Free shipping for many products!

www.ebay.com

here is the photo of the open frame:

HP Agilent 8920A Panasonic TR 60S1A CRT Display | eBay

HP Agilent 8920A Communications Test Set. CRT Display. Item is different from the item that was ordered. Item is not functioning as specified and the item is not sold "As Is". for example, the condition specified is NEW and the item is USED.

www.ebay.com

I once converted one of these little Panasonic VDU's to make it multi-standard, one standard being the old British 405 line system and made an enclosure for it using pre-anodized 3mm thick aluminum panels that I picked up in Akihabara in Tokyo:

https://www.worldphaco.com/uploads/Autodetecting_405_line_monitor..pdf

 

[Hugo Holden]

One other thing, you should keep the VDU, even if you discard the actual CRT(tube) for a couple of reasons, one is parts like the deflection yoke and the horizontal output transformer can be very hard to come by. Also, there are a number of 5" tubes that could be made to work in the VDU as a replacement for the one with the damaged screen. Different types are often very similar, sometimes just a change in the base connections are required, Nearly all (most 5" CRT's) have 12V heaters too, because they were primarily used in portable TV's that were battery operated.

A good source for vintage 5" tubes are early portable TV's from the 80's era, or camera viewfinders . These all have P4 (white) phosphor. If you are choosing one the tube face must have the same perimeter shape and curvature as tour original (later models were rectangular and flat faced (not suitable), a viewfinder like this would have a suitable donor CRT, to double check it requires the schematic of both units to make sure the gun gets wired correctly in the replacement.

Sony DXF-50CE 5" Electronic View Finder Monitor - Sold As Is | eBay

Sony DXF-50CE 5” Electronic View Finder Monitor. This item is untested and being sold AS IS.

www.ebay.com

On the topic of the LInearity Sleeve (you won't find too much about this on the net)

There is an intrinsic horizontal scan linearity problem in all TV's/VDU's. The reason is that the scan from the screen center, to the left, involves the build up of current in the H scan coils, which by its nature tends to taper off in its rate of change with time (an inverted exponential wave). Since the Yoke itself acts to be more sensitive for increasing scan angles, this effects helps the scan linearity on the right hand side of the scanning raster.

However, the resonant process of beam flyback (after the HOT comes out of conduction) reverses the magnetic field to get the beam to the left side of the screen. Then the process of the left sided screen scan is one of exponential decay, as the stored magnetic energy is returned to the power supply, although the initial part is fairly linear. But, this process has a more rapid rate of change of current initially and tapers off a little toward the screen center, because it is, again an inverted exponential.

So what ends up happening is that all TV's /VDU's without H linearity correction have a scan that shows images stretched on the left hand side, because the rate of change of current with time in the h yoke coils is higher, and either normal or possibly compressed a little on the right hand side as the rate of change of current tapers off a little. The 9" PET VDU for example, devoid of linearity correction, always has a stretched scan on the left hand side.

The general method to correct the stretched left sided linearity, is the magnetic linearity coil. It is simply an inductor with a permanent magnet attached in series with the H yoke coils and the width coil. It corrects the current waveform and fixes the linearity defect on the left side of the raster scan, because it is, in itself , non linear.

But prior to this type of coil being common, the other method was a "linearity sleeve" it was a sleeve that fitted around the crt neck, inside the yoke that effectively created shorted turns, to alter the current profile this way, because current in the sleeve generated a reactive magnetic field, to counter that of the yoke. These sleeves are not particularly common and had to be carefully placed to gain good horizontal scan linearity.

It would be a real shame to replace one of the vintage VDU's in these computers with a modern flat screen. Unfortunately they did this at a historic NASA space control center, because it appeared nobody knew how to fix the original CRT VDU's, so they threw them out, installed flat screens in the consoles to impress the tourists. I would have fixed all of them all for free if I had been asked, they were a wonderful piece of space history, now, gone forever.

 

[voidstar78]

@stepleton You more photos of the VDU, hopefully more in the areas of interest.

Image below shows the reflective metal shaft inside the yolk. [ is the LInearity sleeve missing from this unit? I'm not sure ]




Back-side of the PCB (with serpentine "hand drawn" traces?). In case it means anything, on this side it is labeled
1-029-0369 Y
(I've been reading about the evolution of the PCB, very neat stuff)





I'm not sure how to completely remove the yoke portion on the CRT, which has some wires attached to it. So below is the best shot I have of the other side of the PCB. The same label is on this side as well:
1-029-0369-Y

I don't know the full history of this board and CRT (e.g. such as when was the last time it worked). On the right side of the image below, above the 1-029 label, there are some very small holes on the board -- hopefully those aren't missing components?

 

[Chuck(G)]

To remove the yoke from the neck of the CRT, just loosen the clamp at the rear of the yoke and slide it off. Easy.

 

[voidstar78]

I loosened the clamp, but it wasn't sliding off too easy, and I wasn't sure about breaking something. I'll try again a little later when I'm back in.

EDIT: there are two flat circular metal pieces with tabs, so they can free-spin - do those need to be aligned to anything (for removal)?

 

[Chuck(G)]

Those tabs are intended to correct distortion. Leave them alone until you get the new CRT installed.
The clamp can stay with the yoke, but the yoke itself should slide off.

 

[Hugo Holden]

The two metal tabs on the rear of the yoke assembly are beam centering magnets. When they are split apart on their rotational angle it increases the field. If you rotate them both it causes the raster position to rotate. In general they are just manipulated to center the scanning raster on the CRT's face.

If you put in a new CRT, it pays to put some scotch 27 fiberglass tape in the neck of the CRT where the clamp pushes the plastic against the neck. Then very little clamp force is required to stop the deflection yoke from rotating and the plastic tabs sink into the tape a little. Many crts had this tape or similar on the neck to help the issue of clamping the yoke, with minimal force on the CRT's neck.