I have an old IBM 5154 monitor that works pretty well. It only has two issues: the screen is off-center and the color is too blue. I found a service manual for it that describes how to fix both of these problems: there is a H center adjustment and red/green/blue adjustments that can be made to fix the color/temperature.

I know how to discharge the high voltage, I have an isolation transformer, and I've even replaced all of the electrolytic capacitors in the power supply after two had blown up. But, it seems to me, the only way to make these final two adjustments is while the monitor is on...

So, other than using a fully isolating transformer, keeping one hand in my pocket, and not touching anything I don't have to touch, what else should I know or do before attempting this? In particular, I don't see a good way to separate the tube itself from the rest of the electronics, so I may have to reach around them to get the adjustments... thinking I may find a really long plastic screw driver to avoid getting my hands anywhere near the tube.

  • 5
    TV adjustment tools exist (basically all-plastic screwdrivers). I think Radio Shack used to sell them (do they still exist?). I don't know if they can be used live. I don't have a lot of HT experience (especially not recently) so I won't say more. Jul 10, 2018 at 4:16
  • I really wish the GEnie Mac Roundtable were online somewhere. I was walked through exactly what you're doing (but with a Mac Plus) by peops on the forum there. Jul 10, 2018 at 4:19
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    first check if the adjusting potentiometers have holes in the monitor casing. Some monitors and TVs where designed so the adjustments can be done without opening the case. You just put the screwdriver in the hole find the correct position and then adjust looking on the mirror placed in fromt of monitor to see the CRT picture ...
    – Spektre
    Jul 10, 2018 at 8:13
  • It might be worth checking on Electrical Engineering to see if there's a similar question (or perhaps even asking there – but check their help pages first).
    – TripeHound
    Jul 10, 2018 at 8:18
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    Basic, but potentially life-saving, advice: If you really MUST work on live high voltage equipment, always keep one hand in your pocket. That way, if you do get a shock, it's much less likely to go through your heart.
    – alephzero
    Jul 10, 2018 at 10:08

2 Answers 2


Isolating transformer won't help; the HV parts just have to be avoided when making the picture adjustments (mainly, that's not hard). All the red/green/blue circuitry is innocuous circa 50VDC stuff, on the cathode end of the picture tube neck, not as hazardous as the focus adjustment (which is an insulated control) to the only fat HV wire at the neck. None of the bits you touch is anywhere near the HV which is the tube anode (near the screen), but are on the cathode (neck, lower-voltage end).

Few if any isolating transformers can handle the ~20kV that is used on a color picture tube anode.


The plastic screwdrivers you want are known as TV/radio alignment tools. Searching on those terms will turn them up. Radio Shack (RIP) sold a kit for under ten dollars; Amazon has sets starting in the same range. The cheap ones wear out quickly, but they should last long enough for what you need to do.

These protect you from high voltage, and they also help keep your body's capacitance from throwing things off. That's especially important when you're adjusting a trimmer capacitor.

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    ...and they also are non-magnetic! You don't want to bring any ferromagnetic object (whether or not it has any residual magnetic field of its own) near to the tube when you're adjusting geometry and color. Jul 10, 2018 at 16:43

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