EQ problem with Mark IV Short Head

I recently purchased a Mark IV head on craigslist for a good price because they guy explained that the graphic EQ has some issues. I've played other IV heads and I knew right away this one was "off" but I figured I would work with it.

Head serial number is: 010183


problem: The Graphic EQ just seems "off", not broken. I play for high gain metal, and when dialing in the V-shape EQ, it has a total boomy and under water tone. No matter how I adjust any of the knobs, the V-shape EQ just sounds horrible, which is unlike any IV head i've played. What could be the issue here? Something with the inductors?

Set it flat. Slide each control up and down one at a time while playing. Are there any that do nothing, or almost nothing? Are there any that are way more powerful than the others or act differently than you expect (high EQ affects low frequencies, whatever)?

You may have a bad circuit element, or it may be as simple as a bad solder joint. It will help to narrow down the source.