ADCOM GFA-555! - Fuse replacement and Bias Check plus Audio Demo

[@wayneessar7489]

It (she) sounds wonderful through your phone and out of my old tablet so it must be very fine in person...! Thank you for showing it...!

[@bblimediamostlyspeakers]

It is a very clean amp! Thanks for watching!

[@AtariCentauri30]

I have the 555ii and it is a great amp. I use the Adcom gfp-750 preamp with it and i feel it is the best bang for the buck.

[@jimwenzel5523]

I need to replace the red pilot light in my GFA 555. Would you know what voltage is would take

[@bblimediamostlyspeakers]

Not off hand without tracing the line back. However, these were made in the 1980's as you probably know, and the pilot light is an LED. Early LED's could not tolerate much voltage, I think they were about 1.5 volts. There should be a dropping resistor in line, and then runs back to the power supply board. It is possible that something on the driver board is not feeding voltage to that LED. I replaced the power switch on mine, if you dont mind yours being not quite original, you can probably drop in a new lighted power switch.

[@jeffreylonigro1382]

You seem to know what you are doing, so why would you replace a fuse without determining what caused it to open?

[@bblimediamostlyspeakers]

Well, I don't know everything about electronics repair. I do know enough to break stuff :) I also know exactly what blew the fuse. The place I got the amp from was using it as a PA amplifier. Since this amp is a high current design, in a PA setup this amp simply fed enough power to blow the fuse. Now they are using a proper PA amp, and I have a great sounding HIFI amp.

[@jeffreylonigro1382]

@@bblimediamostlyspeakers Ok, so you knew the issue. Cool. Nice amps. Very well designed and built. They are workhorses.