I like this power supply. I replaced the caps and 1 transistor and its been working for a long time. Its perfect to run a MCU, TTL, or small electroplating and LED's. I also varnished the transformer on mine and greased the potentiometers.
Its a bit annoying to work on but I think its a nice supply. You get pretty fine adjustment because the range is so small, and you won't burn out too many parts by accident. Its very nice to adjust if the potentiometers are good.
As always, more supplies is better then better supplies if you do complicated things, i.e. isolation circuits or multi rail circuits.
Alot of modern op-amp circuits, MCU, and even small FPGA are happy with it. The 0-5V op amp craze for instance. At 3 amps you get quite a bit of juice for those types of circuits.
Usually they are filthy though, so you need to wash it good and dry it out.
$10 is a excellent deal for it.
Specifics that might help you
1) transistors in back on the heat sink are the first thing that usually breaks in harrisons
2) the solder joints around the PCB mounted transformer (rivets) can go intermittent open circuit and drive you insane if you don't figure out that they might be the problem
3) if it makes noise in your house, its often not the transformer but the SLCC disk capacitors on the supply. The caps are fine, just the power grid sucks nowadays... you can replace them with metal film and its quiet, but the filtering won't be as broad band theoretically. I often wondered if I should put say the 100nF foil and then a 1nF SLCC in parallel with it. The single layer caps are very broad band (into the GHz), other then lead resistance. I read they can perform to many GHz if you use them SMT style (remove leads and solder them like a coin standing upright). I believe this is still used for microwave coupling caps.
4) careful tuning, I have seen the current jump way up on the current limiting potentiometer.
If they went with a thicker PCB on this unit for the transformer, or improve the brackets, this thing would be even better.
I will actually go and use this supply if I need 5V or 3.3V... its actually my first choice for that. Every power supply after this one is just bells and whistles