IBM 5151 monochrome monitor "tired"?

[tony359]

Hi all,

I have inspected a 5151 monitor - I thought it was faulty but then I realised it won't switch on without a signal

The monitor works but it's a bit soft. I adjusted the FOCUS trimpot and it's maxed out to one direction and I don't get to a point where the focus "gets better and then worse" if you know what I mean. I can turn and see minor improvement and then the adjustment stops *before* it gets worse.

Could this be just a tired CRT or could it be a tired capacitor? I don't see electrolytics on the Focus line.

Also the monitor has an horrendous phosphor retention! If I DIR a folder it takes about 2/3 SECONDS for the phosphors to fully fade out! Again: tired CRT or maybe a tired capacitor? Or maybe this CRT has always been like this?

Clip attached. Image is intentionally overexposed but that's how it looks with naked eyes.

Can someone familiar with this monitor comment please?

Thanks!

 

[mbliss11]

My 5151 has a similar retention time to your video. Think that’s just how they are. Someone had made a matrix scrolling text demo specifically for this monitor by removing “fade” effects that were in others.

As for sharpness not sure. Have you shot the pots with deoxit yet?

 

[maxtherabbit]

the long persistence phosphor is by design

 

[booboo]

Yeap, that's what a 5151 phosphor persistence is supposed to be like... miss that monitor.

 

[andy]

You should check the voltages in the focus circuit against the schematic. It looks like one end of the focus control should be +450v, and -170 on the other. Knowing which end you're maxed out at will narrow things down.

You should also check for out of tolerance resistors in the same circuit. Also, make sure the focus control itself is good.

 

[Nama]

Exactly as my two 5151 monitors do

 

[offensive_Jerk]

You know where I can get that matrix demo?

 

[offensive_Jerk]

Nevermind, it's digirain on GitHub.

 

[mbliss11]

Nevermind, it's digirain on GitHub.

Yep! It’s a cool demo and looks great. I built a pc sprint for my 5160 and used it originally to test that my turbo switch was wired up correctly. Now I use it to run a load on the machine every few weeks or so

 

[offensive_Jerk]

Pc sprint? Haven't heard of it, but sounds interesting.

But I did compile digirain last night and ran it on my 5170 with amber monitor. I need to try it with my 5151.

 

[mbliss11]

Pc sprint? Haven't heard of it, but sounds interesting.

But I did compile digirain last night and ran it on my 5170 with amber monitor. I need to try it with my 5151.

PC-SPRINT - Overclocking The First PC With A DIY Open Source Hardware Solution From 1985!

Join me as I tell you all about the PC-SPRINT. The plans for this DIY overclocking solution were released for free in 1985, so I decided to build one in 2020 and use it to overclock my 1981 IBM 5150 PC!

ctrl-alt-rees.com

Yea really cool mod. Huge performance boost for 8088 pc’s

 

[tony359]

ahaha the monitor with the built-in Matrix effect! Fantastic! Thanks for confirming.

I shall check the voltage values as per schematics. Chances are this is what the monitor can do but I can check!

Cheers!