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Commodore PET 2001-8C with blue phosphor screen?

B

bleep

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Hi gang, after buying a PET 8032 the other day, I decided to dig out the other PET I have had in the attic for ages.

Turns out it's a PET 2001-8C, in quite nice shape except for the front label missing:

IMG_1273.JPG


It turns on and shows a more or less expected garbled screen. I'll get to fixing it later, but for now I wondered about the blue phosphor screen. I usually see white or green, but this is distinct blue. It doesn't turn to white when turning up contrast. Photos of low and high contrast settings, high contrast might seem white-ish, but in real life it's very blue:

IMG_1273.JPG


IMG_1274.JPG


Anybody know if there's anything special about this?
 
Please take a picture of any label on CRT, that might shed some light on what that actually is.

Frank
 
Off hand it will have a P11 phosphor.

Blue was not that uncommon for some CRT's for photographic applications, it has a shorter persistence than green (P1) or white (P4). It is relatively rare though for an electromagnetically deflected CRT, most CRT's I have with P11 are scope style electrostatic CRT's.

So the CRT type is likely "somethingP11", or possibly a P5 phosphor.

Here is a good phosphor list:

http://www.bunkerofdoom.com/tubes/crt/crt_phosphor_research.pdf


(The other options to explain it, it could be a color CRT with the blue gun on , but I cannot see a dot pitch style phosphor in the photo, or a hoax/shenanigans as suggested by VERAULT in post #2 , with say a blue filter in front of a P4 white CRT, but I think not, and that suggestion might impune the OP).

If this is a blue CRT in the PET as it appears, then its super cool in my opinion.
 
Sanity check. Is this a regular CRT with a blue filter in front of it? Something about the images seems off to me.
 
It doesn't even look that real to me. Clear, square pixels don't come from CRTs. CRT faces aren't that flat. Blue CRTs don't generate both blue and cyan on a PET.
 
NeXT said:
Sanity check. Is this a regular CRT with a blue filter in front of it? Something about the images seems off to me.
Click to expand...

There is perhaps a tiny blue glow from the screen filter. So its either a white CRT behind a blue filter or a blue CRT behind a clear filter, but the OP could tell right away just by shining a torch at the filter.
 
Screenshot_20190928-230024.jpg

That's not a CRT.

But the forum won't show enough clarity in my image so you'll have to zoom in for yourself.
 
It fills me with joy that shenanigans are considered a possibility in the world of microcomputer enthousiasts! But I can asure you, not pulling anyone's leg here.

I see I posted the wrong link for the first photo, but I can't edit my post (nor see the photos myself, nor see my replies as I'm new to the forum...)

So here's more photos: https://pixelambacht.nl/dump/pet/2001-8c

Here's one photo of the PET:

IMG_1277.JPG


You can see the blue gloss on the screen when the computer is turned off. It looks like there's maybe a blue layer in front of the screen -- I didn't mean to imply the phosphor is actually blue. I called it that to distinguish between the "blue monitors" that this version has, with blue plastic instead of actual blue screen.

Anyway, I hope these extra photos shed some light. The PET is back in the attic but I don't mind taking extra pictures.
 
KC9UDX said:
View attachment 56338

That's not a CRT.

But the forum won't show enough clarity in my image so you'll have to zoom in for yourself.
Click to expand...

I'm still of the opinion for now that the OP is genuine with the post, who would make a hoax out of the notion of a blue CRT in a PET ?

Also when I look closely at the photo, in the areas that are very bright I can see definite scanning lines with the usual spaces between them, typical of a monochrome CRT.

So I think it's either a genuine (rare) blue CRT, or a white CRT with a blue filter over it.

But, if I have been fooled, it's a very strange joke.
 
Hugo Holden said:
I'm still of the opinion for now that the OP is genuine with the post, who would make a hoax out of the notion of a blue CRT in a PET ?

Also when I look closely at the photo, in the areas that are very bright I can see definite scanning lines with the usual spaces between them, typical of a monochrome CRT.

So I think it's either a genuine (rare) blue CRT, or a white CRT with a blue filter over it.

But, if I have been fooled, it's a very strange joke.
Click to expand...

But look at the pixels. A CRT produces round pixels. Those are very well defined rectangles with sharp edges, such as an LCD produces.

I'm not saying the OP is trying to pull one over on us. But maybe someone has refitted this PET with an LCD. Or somehow bizarrely the camera makes it look this way.

EDIT:. Ok, it's the camera. Mine does this too, apparently. It probably is a blue CRT. We need to see that CRT label sticker.
 

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How could some white phosphor PET CRT's looks bluish and some do not ( for the record the OP's isnt Bluish... Its outright Cobalt!) My PET 2001-8 is just white... no hint of anything else.
 
P4 looks bluish if you turn the brightness down. But not that blue.

I suppose it also depends on what you compare it to.
 
There were at least three versions of P4 phosphor I have seen. The early ones from pre WW2 CRT's for TV use emitted a white light only and were easily burned by the electron beam. Dumont had their own formulation of it that has a subtle yellow tint.

Nearly all the post WW2 P4 phosphor (for TV use) has a similar formulation. It contained micro-granules of a blue and and a yellow phosphor, giving a white light effect, not quite white though, resembled a silvery moonlight. If you look at a working B&W TV set, under high magnification, with the phosphor illuminated, you will see the fine yellow & blue granules.

However, the vivid blue seen in these Pet photos is most likely a P11 phosphor.
 
The OP is probably still moderated, so he changed the linked image to point at a bigger picture collection that's linked here:

https://pixelambacht.nl/dump/pet/2001-8c/

Judging from the other pictures, I'd say it's definitely white phosphors with a blue plastic screen in front of it.
He didn't remove the back of the monitor case to take a picture of the CRT label anyway.

It has the 2001 6550/6540 motherboard in it.
Please, if the owner reads this: remove all the dust from the motherboard :)

The issue with these motherboards are more likely due to some of the 6550s and/or 6540s failing. I have made several videos on youtube about identifying and troubleshooting issues on those 2001 early motherboards.
Frank IZ8DWF
 
iz8dwf said:
The OP is probably still moderated, so he changed the linked image to point at a bigger picture collection that's linked here:

https://pixelambacht.nl/dump/pet/2001-8c/

Judging from the other pictures, I'd say it's definitely white phosphors with a blue plastic screen in front of it.
He didn't remove the back of the monitor case to take a picture of the CRT label anyway.

It has the 2001 6550/6540 motherboard in it.
Please, if the owner reads this: remove all the dust from the motherboard :)

The issue with these motherboards are more likely due to some of the 6550s and/or 6540s failing. I have made several videos on youtube about identifying and troubleshooting issues on those 2001 early motherboards.
Frank IZ8DWF
Click to expand...

Frank you solved the problem! From the link in your post, image "IMG_1265.JPG" the blue filter is completely visible.. its a plastic insert! That's all it is.

Edit: After looking at image"IMG_1275.JPG" I see the CRT bezel which is black is not the correct shape. It looks like a windshield! the whole front bezel with the black border must be a snap on overlay.
 
KC9UDX said:
But look at the pixels. A CRT produces round pixels. Those are very well defined rectangles with sharp edges, such as an LCD produces.

I'm not saying the OP is trying to pull one over on us. But maybe someone has refitted this PET with an LCD. Or somehow bizarrely the camera makes it look this way.

EDIT:. Ok, it's the camera. Mine does this too, apparently. It probably is a blue CRT. We need to see that CRT label sticker.
Click to expand...

I'm walking in halfway through this conversation, but I can tell you that I for sure used a PET with blue-ish tinged characters back in the late 1970s, so there definitely are such critters.
 
Yes, this is not that blue. I can't even come close to white. The original post should've had the first photo of the machine itself, and the second and third of the blue screen on min and max value, respectively.
 
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