FIXED: VR15 (Hi Tom Tune) does not do anything.

VR15 (Hi Tom Tune) does not do anything.

However when I short pins 1 & 2 of the pot, it does work, sorta
I made a recording of it (while shorted):
https://soundcloud.com/rvooh/yocto-ht-shorted/s-n9ycD

I was suspecting the pot to be the problem, hence I already started a topic to find a replacement: Tom tune replacement pots
But now that I measured the pot in-circuit, it behaves exactly the same as the other (working) pots of same kind (LT, MT) (measured between pin 1 & 2 and it goes from 0 to 0.5k)

Respective continuity between VR15 pin 1,2,3 and surrounding components was also tested and seems fine.

Rather clueless. If anyone has other suggestions, please tell me.

Thanks in advance!

Hi!

A typo I guess, VR14 is the Hi Tom's volume pot, A104. VR15 being the tuning pot value 500R.

I'm not that sure, my guess would be to check D84 and then D85 (Germaniums) to make sure they're the right way round, with the two red lines matching the white one on the silk screen.

Hope this is of some help.

jeremy wrote:Hi!

A typo I guess, VR14 is the Hi Tom's volume pot, A104. VR15 being the tuning pot value 500R.

I'm not that sure, my guess would be to check D84 and then D85 (Germaniums) to make sure they're the right way round, with the two red lines matching the white one on the silk screen.

Hope this is of some help.

Hi jeremy, indeed I had a typo, corrected it now. Thanks
Well, the germaniums are the right way round, I also tested them in circuit with a diode tester and it seemed ok (although: In circuit might have been a mistake?)
Someone else told me if those diodes would be wrong or broken, I wouldn't get a pitch change when shorting 1&2.. but not sure of that's true.

You can't measure them in circuit because they are both in paralel with each other and facing the opposite direction so you'll have lift the lead of each diode at one side to make a proper measurement.

I think that it's probably U18 that went bad or something.

Hey guys, a small update..

Desoldered the diodes, they're both fine. Put them back in.
Desoldered and replaced U18, same result as before.
Desoldered VR15 to test it out of circuit, passes tests perfectly, nothing wrong with it.

Thanks for the suggestions though, I can only try..

Great news, it's fixed
Thanks to a suggestions from altitude on irc to check the resistors

I had swapped R278 and R287.. so stupid 22k vs 1k... but hey, it works now!

Thanks for the help guys!