Modified power supply Pyramid PS-52KX

[Jack Crow]

Hi all,
Just finished working over an old power supply for improved performance and digital meters.
This thing was in service every day for years in my clients ham radio room. So it collected it's share of dust and ware.

Un related to 3d printing had to fix issues with the OEM's assembly methods.
To keep to a price point, the factory used point to point wire work, so they soldered directly to the output transistors.
They also used black anodized screws. They don't get a good 'bite' on the metal case of the transistor and therefor do not pass current well.

I updated this by removing all the wires and heat sinks.
Once I had it apart, I tested all the output transistors before re assembly.
These things can and do go sour so it pays to check before all the rework.
Re drilled the heat sinks to accommodate transistor sockets, and re assembled with stainless steel screws and new heat sink compound.
Bright metal conducts current much better than what was there.

Then I had to figure out how to add new meters to the unit.
Done this before with Astron power supply's, so this is not all that hard. We do get better with practice.
Had more space with this PSU, but had to be careful not to cover the silk screen graphics on the front.

As built, the PSU held two big analog mechanical meters.
They were attached by two screws that went through the front panel.

Designed and printed a new two part meter holder.
The back part that actually holds the meter is centered into position by making use of the OEM's attach screws.
Those are to the left and right of the meter face.
The front part is a frame held in place by four 4-40 hex cap screws.
Over kill sure, but it looks cool.
Clients like to have cool gear.

The left meter is an AC line voltage monitor meter.
The right is a DC volts and amps monitor.
That connects to various points in the PSU including a new current shunt that I attached to one of the heat sinks.

This is the front view of the modified PSU. AC volts and DC meters are on and functioning.

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This is the back view of the DC volts and Amps meter.
Little tip, that black plastic housing under and to the left, is a snap on ferrite bead.
Do be sure to use ferrite beads when adding digital meters to existing gear.
It helps to keep EMI and RFI out of the meters.
The meters were intended to be used with industrial applications, not so much in a radio frequency environment.
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Front view of the DC meter. Spiffey!
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This is a close up of how the shunt was installed.
Ordered a shunt with an injection molded black plastic insulator.
Some on Amazon lack this insulator and make mounting the shunt much more difficult.
Drilled some pilot holes in the heat sink, and shot in some screws. It's going no place.
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This AC meter fits the same plastic part.
Here is a soft focus back view. Real sorry about that.
I am not taking the thing apart again for a second go with the camera.
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AC meter front view.
Same printed plastic front and back. Same hex caps.
Using the same family of meters for a project cuts down the re design requirements.
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So that is what is going on.
Glad to get this off the desk.
Have some improvements for the power system on the Simple Metal printer (see posting in trouble shooting area).
Another client dropped off an Astron for fixing, will see to that as well.

Have a few printer projects in the works, but none are ready for 'prime time' here.

Hope all is well on your end.
Jack Crow aka Radio Mike in Virginia Beach