Hi looking to see what to test for in a dead Varitone circuit from the ? late 70s.
This is in a guitar that has been stored for 20yrs+ and whilst there is output and all pots work, there is no tone change when the Varitone selector is moved around. it did work pre storage .
It looks to be the classic Gibson style circuit with caps and resistors wired in parallel with ? 100ohm final resistor and small inductor producing the notch filter arrangement.
Any advice in bringing the circuit back to life would be appreciated.
guessing this is the circuit , with Gibson’s “accidental” labeling of the inductor value as 1.5h
Comments
I would guess the problem is corrosion either in the switch contacts, or the choke.
Try touching the terminal where the grey wire goes between the rotary switch and the choke, with the guitar plugged in - if you get a buzz, which changes with the varitone position, it's the choke. If you don't, it's the switch. It could also be a failed solder joint but they do look OK - unless it's where the ground wire from the choke goes to.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
It’s a guitar I co-designed for my 20th birthday and had made in USA when I was there… it’s not great at all ( hence the storage) but I’ve dug it out and I’m determined to get it as good as it can be.
if you know of a design of Varitone ( with or without choke ) that would just give me some subtle variances from sweetening to cocked wah without mud, let me know.
regards
mike.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
i love a bit of counter espionage from Gibson back in the day .
So happy to get a neglected old guitar back to full electrical health.. now the hard work begins with the actual playability