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Rotate an external CRT connected to old IBM 5110

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voidstar78

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I picked up an old Sony CRT to connect to the external BNC port at the back of an IBM 5110. And the output is ending up 90degrees off.


I've used a BNC to VGA adapter in the past, and the output is the correct orientation there. So I don't think the issue is on the 5110 side.


Can I open this CRT and physically rotate the tube?

Or were than any adapter things to put inline to the BNC cable to adjust the signal?



SONY_CRT_wrongway.jpg
 
It's not the tube that needs rotating, it's either the yoke needs to be rotated around the neck of the tube or someone miswired the horizontal and vertical deflection wires to said yoke. Unless this monitor has a switch hidden on it somewhere to run in rotated mode.

(I mean, for sanity's sake feed something else into the monitor to make sure it's consistent, but I'm sure it will be.)
 
I'll see weird things like that happen for people who are playing vertical arcade games but not on tubes that small. For those you just put it on its side LOL!
 
There are the normal adjustment knobs at the front (brightness, centering), then there are two sunk in knobs at the back - the two in the back just adjust the "height" of the characters and "something else" (I forget exactly, but nothing to do with rotation). On the BNC connector (i.e. the metal plate surrounding the two BNC connector - one input, one output) there are a couple switches also (forget what they were labeled, not home at the moment), I flipped those also but just call they also had nothing to do with rotation.

Alright, no simple solution, looks like I'll have to go inside this thing :D Will report later on how that goes.

EDIT: Oh, and to find another BNC output device to plug in, to truly verify not an issue from the 5110 side.... TBD, I'll see what I can find.
 
I couldn't find a different BNC output device. I thought my old 1980 ColorComputer might do, but couldn't find a suitable adapter. All I can say is that each of my 3x 5110's have the same result, so it's not just that single one machine at least. I do have a Function generator, but I wasn't sure what a "normal" signal out of it should look like on a CRT.


BTW: I read something from back in 2007, someone suggested that the change in the magnetic pole of the Earth could cause this kind of flip in some CRTs (for certain old devices) -- that had to be like an April Fools tease, right? I know the poles of the Earth do wander, but we're talking across thousands of years, not 30-40 years.


So, are these the wires proposed to be swapped? Would I swap Blue with Green and Red with White? Do these look like after-factory re-solders?

Alternatively, suggesting to loosen the screw and spin the yoke? (with precautions, like wearing rubber gloves and discharging components)

1665221427442.png
 
Don't swap the wires. The horizontal and vertical deflection coils are not the same. Swap them and you will let the magic smoke out.
Look at the wire gage. ... Not even close to the same.

Just turn the yoke.

joe
 
Done :)

Thanks! That white plastic helm made it easy to turn.

IMG_3758 - Copy.JPG



How would a consumer (non-commercial, not a lab) get one of these in the 1970s? (or something like this, with a BNC input) As in, what catalog or store would they go to?
 
voidstar78 said:
There are the normal adjustment knobs at the front (brightness, centering), then there are two sunk in knobs at the back - the two in the back just adjust the "height" of the characters and "something else" (I forget exactly, but nothing to do with rotation). On the BNC connector (i.e. the metal plate surrounding the two BNC connector - one input, one output) there are a couple switches also (forget what they were labeled, not home at the moment), I flipped those also but just call they also had nothing to do with rotation.

Alright, no simple solution, looks like I'll have to go inside this thing :D Will report later on how that goes.

EDIT: Oh, and to find another BNC output device to plug in, to truly verify not an issue from the 5110 side.... TBD, I'll see what I can find.
Click to expand...
BNC is just a different connector type for composite video. You can hook up a VCR, Nintendo, etc to that monitor with a BNC to RCA adapter.
 
I found an old 1975 JVC catalog that is listing these TM-600 and TM-900 models (I assume 6" and 9"?). Why do these monitors say "for commercial use only" on the back? Were retailers legally required to only sell them to commercial business?

There are no prices on this JVC catalog. But there was another catalog (no photo) that had a price like $795 or so - is that approximately accurate, that these "monitor TVs" were pretty expensive then (pre-1978)? (in contrast, like a 21" home color TV around then might be about $500?)


1665253185714.png


By 1978 I'm sure prices had come down (the Apple 2 included a 9" monitor with its ~$1300 price, as did also the PET and its base model was ~$795; IMO, the PET screen was pretty decent quality, but maybe not a lot of adjustment options {couple knobs at the back} -- not sure what the quality was on the Apple 2 initial standard screen).

Anyway, was just curious how someone in 1975 would exercise the BNC output of the IBM 5100. A "regular TV" might work with adapters, but it might not be centered or scroll right? (and not enough adjustment options to compensate?) More likely, you'd need a monitor with the various adjustment knobs, to get things centered, scaled, and stable (non-scrolling)? So as I see it: if lucky, your business/department already had something suitable (from other projects/equipment), or you'd have to justify spending another $800+ to get one (in 1975).
 
Tuner-less monitors were considered “commercial use only” in the early 1970’s simply because nearly no consumer equipment existed that used raw composite; the primary uses for them were TV production and closed circuit/security video applications. In spite of the stickers there was no law preventing a mere mortal from buying one, and when “personal” computers started being a thing they were easy enough to buy mail order, from the early computer stores, or from AV shops if you happened to have a store carrying such things nearby… and they could be had for a lot less than $800 if you went with a lower end model. (Like that Sanyo monitor often pictured with Apple Is and early II’s; smart shopping could get you one for less than $200 even in 1975. I would guess the difference between that $800 JVC and the Sanyo is the JVC was aimed at TV studios and the Sanyo at mall security and warehouse applications. Which is fine, the warehouse monitor is good enough for the crude video being spat out by those early computers.)

And has already been noted, the signal on that BNC connector is the same composite signal as the yellow RCA jack on later consumer monitors. The BNC jack has better signal integrity than RCA, but it’s more expensive and confusing for mere mortals, which is why it’s limited to ”commercial” equipment for the most part. For less than $5 you can get an adapter to plug consumer composite into that monitor. I have one of these hanging off the 10” mid-80’s color Panasonic “professional“ monitor I use with my Apple II+.
 
Last edited:
voidstar78 said:
Done :)

Thanks! That white plastic helm made it easy to turn.

View attachment 1247140



How would a consumer (non-commercial, not a lab) get one of these in the 1970s? (or something like this, with a BNC input) As in, what catalog or store would they go to?
Click to expand...
I worked at a TV station in the early 70's. We used small monitors by the pallet load. Every system had four or more monitors attached.
There were vendors that specialized suppling TV equipment. So not hard to find.
The security CCTV companies also used them by the truckload.

joe
 
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