TEK PS2521G
TRIPLE POWER SUPPLY
Tektronix PS2521G
The TEK PS2521G is a great triple power supply. Almost. But here is how to make it perfect.
The good: 3 supplies in one, digital, precise to 4 digits in voltage and current, settable by HP-IB, quite powerful, very quiet.
The bad: fan is incredibly loud, and the "on" LED is one among many red LEDs that look the exactly same, and is near impossible to visualize.
It's actually made by Instek (in Taiwan?), and that's how you find the schematics.
Tek PS2521G Repair and Upgrade video
I repair my PS2521G supply, and upgrade the fan and the on light
Tek PS2521G Documentation
Fan and Caps Replacement
The fan replacement I used was this one on Digikey:
https://www.digikey.com/en/products/detail/delta-electronics/AFB0824L-F00/9478117
It is no longer available, so you'll have to look for something similar, same dimensions, similar noise, similar pressure. Spec sheet below.
I used these long life Rubicon caps for the replacement: 470 µF 35 V Aluminum Electrolytic Capacitors Radial, Can 10000 Hrs @ 105°C
https://www.digikey.com/en/products/detail/rubycon/35ZLH470MEFC10X16/3563723
The LED frame printed on a transparent label that I used in the video is also available below, the .lbx file is for a Brrother P-touch label maker.
Blinking "On" Light
In the video, I try to solve the ON light LED problem by changing its color to make it more noticeable, but none of the new colors make it through the red front panel filter. Instead I resort to draw a little frame around the LED. But viewer Jim Flanagan had a much better and much more elegant solution. He reversed engineered the firmware, and modified the ROM so it would make the red LED blink.
You need to burn them in a 32k EPROM, a 2732 is perfect.