I have a black grill 112 RD50 (1984 I think) that I bought used a couple of years ago. At the time I purchased it, I was told it had a recent re-cap and all was good to go for a while. After using it a bit, I noticed a slight distortion that was hard to define. It seemed to ride the signal, as the amp was quiet for the most part when idling, but occasionally would exhibit a static noise even with no signal. Last week I opened it up and found the electrolytic caps all replaced as described with Sprague Atom caps. I found the JE1692 transistors were also replaced with a NTE196 type, so I ordered some 2N6488's and replaced them. I replaced all the tubes with JJ's, and replaced the original ceramic speaker with a new Jensen Alnico 5.
Pretty sure the distortion is gone now and the amp is super quiet, but it seems very crisp and heavy mid range. The treble control operates as expected, but the bass control does nothing. Either channel has the same behavior. I haven't taken it out of the cabinet yet, it seems odd two separate circuits would be affected the same way.
Can anyone steer me in the right direction?
Any and all suggestions and comments are appreciated.
Thanks in advance for your help.
112 RD50 bass control has no effect