NFB Variable pot problem ?

[Ang3lus]

Hey all,

I have a 102 which is quite a few years old, been working great but i want some more versatility out of it.

I built it with no mods per the layout, and i've come across a weird problem, i tried adding a NFB pot, and when i measure from the pot to the speaker jack (or nfb wire) i get 390 ohms. ok... i said, i put back the 4k7 nfb resistor, and still i read 390 ohms (from the 4k7 resistor to the jack), no matter what i do, that's what i get.

I disconnected the NFB wire, and it reads perfectly fine, 4k7 with the resistor and whatever i get with the pot, so it must be when i connect the nfb wire to the speaker jack that it somehow parallels the 390 ohm resistor ? (which i guess is what resistor in parallel to the presnece pot ?)

is something really wrong here ?

[sluckey]

Nothing wrong. Look at the schematic and you will see a 390Ω in parallel with the 4.7K.

[Ang3lus]

So is it even possie to change the nfb ? Will it have any effect ? With the variable resistor ?

[pdf64]

You may be attempting to make an in-circuit resistance measurement of parts for which parallel resistance paths make that highly inaccurate.
The OT secondary winding uses a short length of thick wire, and so its resistance is very low.
What is actual issue, eg did the nfb control not do anything?

[Ang3lus]

It didn't, but I suspected a cap was behaving badly, checked everything except the pi coupling cap, the nfb side wasn't good, now all is working again