IBM 5150 Line Voltage

[paul]

My 5151 is 240v. I'll have to be damn careful not to plug it in to the 5150's PSU.

I very much doubt you will damage your 240V 5151 by running it on 110V off the PC for a short time - it just won't work. What is damaging is driving it at a significantly-wrong horizontal scan rate for a length of time, which I've had happen when a program went haywire.

It's really absurd that IEC connectors have the same pin arrangement for both voltages. Less of a problem with modern equipment but a poor standard to start with.

FYI, conversion steps for 5151 to world-wide voltage. http://www.vintage-computer.com/vcf...ert-to-worldwide-voltage&highlight=*paul+5151

 

[Stone]

There is no switch on a a 5151 to turn it off or even a light to let you know it's running. Quite easy to leave the thing turned on for days without even realizing

Not, it isn't. The 5151 requires both AC power and video signal to turn it on. When you unplug it from your video card... what happens? So, if you turn the computer off the monitor goes off as well, even if the AC line is still alive. Check the filament on the tube.

 

[modem7]

Not, it isn't. The 5151 requires both AC power and video signal to turn it on. When you unplug it from your video card... what happens? So, if you turn the computer off the monitor goes off as well, even if the AC line is still alive.

The circuit diagram for the 5151 indicates that with mains AC power applied to the 5151, and not connected to an MDA card:

1. The 5151's power supply generates +15V.
2. One of things that the +15V powers is the CRT's heater (via a drop-down resistor).
3. One of things that the +15V powers is a +5V generator for the first stage of the video circuitry.
4. One of things that the +15V powers is the vertical deflection circuitry (TDA1170 and associated circuitry).

Other DC supply voltages are not generated until the horizontal sync pulses are fed to the 5151.

So, I think it it fair to say that a 5151 with AC power applied, and not connected to an MDA card, is partially on.

Check the filament on the tube.

See [here]. On the 5151s that I have been exposed to, an operating filament can only been seen when the 5151 is opened.

 

[Malc]

You could always get a new fan for the 5160 PSU, Get a decent one and it'll last for years and are sooo much quieter, Open the PSU and see what type it is "AC" or "DC" and start googling, They are not that expensive and the 130W PSU was a common upgrade for people fitting a power hungry hard drive to their 5150's back in the day.

... I do have a spare 5160 power supply, but it's the model with the loud, high rpm fan...

 

[vwestlife]

So, I think it it fair to say that a 5151 with AC power applied, and not connected to an MDA card, is partially on.

I can confirm that with AC power but no video signal, the CRT filament glows, but there is no HV and no raster on the screen. Once you apply a video signal, an image will appear on the screen instantly, because the CRT is already warmed up. (That's the way "instant-on" TVs used to work back in the '50s, before they fell out of favor due to them starting fires and burning down houses. :shock: )

 

[paul]

After quite a few hours of work I've managed to convert one of my 5150 110VAC power supplies to run on 230 VAC with about $15 of replaced parts. Will have to do more testing to ensure it's reliable.

I have two US-spec 5150s that I've run for a decade on a step-down transformer via 240VAC/50Hz. That's not the problem - the problem is if one day you (or someone else) forgets to use it because you are so accustomed to IEC plug cords going straight into the wall.

 

[Malc]

Interesting, I don't personally own any 110VAC machines though would like to see a write up of what was involved if you get around to it.