TAPCO 4400 Stereo Spring Reverb
Handled the grounding first and wired grounding wires to one star spot close to the power-entrance to remove hum. There was several potential ground-loops, so I also removed the screws that made contact between pcb-ground and chassis.
Next, I put in +/- 18V-regulators and bigger caps in the powersupply, plus a 100nF filtercaps to ground. didn't hear any difference, but a cleaner DC power doesn't hurt.
The VU meter looks cool, but unfortunately it brought distortion back to the audio (on one side), so I decided to disconnect it. Maybe there's a short somewhere to the audiochain.
Last, but not least, the caps were changed and the 5K sliders was changed to 10K sliders. The unit dates back to 1976, and the connectors needed a good cleaning. The Tapco4400 is a brutal kind of spring reverb. And with a strong boosted input - it goes SPIOOOONG. With the 4band EQ you can shape it's sound, and since the actual springs are so big, it is mainly used here for extreme reverbs and 'creative'-effects. - I dig it on perc stuff, woodblocks etc. and dessert-guitars