Crack build resistance check

[ekzotic]

Hello! I finished my first diy build and did resistance check and some readings don't look right. Any thoughts?

I used terminal 12 to test.

3,8,12,14,20,22,RCA ground - 0.5
RCA right - 92k
RCA left nothing (can't measure)

All the others look fine.

[Paul Birkeland]

0.5 Ohms is pretty close to 0 Ohms.  What do you get when you just touch the probes together?

No measurement on the left RCA jack makes me suspicious that you might be missing the jumper that connects both terminals on the pot where black wires land.

-PB

[ekzotic]

Hi! Thanks for the fast reply.

Tried to measure probes together and got 0.5

It is not very clear to me what jumper do you mean? English is not my native language.

[Paul Birkeland]

See page 21, first instruction, red and black arrows.

-PB

[ekzotic]

I have that jumper installed and tried to measure it and it showed 0.5 on the top and the bottom.
Red terminals show 2.2 in the middle and 92k.
White show nothing.

[Paul Birkeland]

White show nothing.

What does the meter actually say?

Can you measure the resistance between the two white wires on the volume pot?

[ekzotic]

Resistance between the white wires 90k.

What does the meter actually say?

Meter show 1, it's a cheap chinese one.

[Paul Birkeland]

I would try reheating both solder joints with black wires on the pot.

-PB

[ekzotic]

Tried to reheat and nothing. 

[Paul Birkeland]

Go ahead and fire up the amp with no 6080 and just a 12AU7.  You either have a defective pot, a defective meeter, or a flaky solder joint.  More information may be obtained from a voltage check.

[ekzotic]

Can you explain more how it works? Should terminals on the pot with white wires measure 0 to the ground?
I'm going to make a voltage check tomorrow.

[Paul Birkeland]

Can you explain more how it works? Should terminals on the pot with white wires measure 0 to the ground?
I'm going to make a voltage check tomorrow.

The terminal with the black wire should show 0 ohms.
The middle terminal with the white wire should show 0-110K, depending on the position of the volume control.
The outside terminal with the white wire will show a static value somewhere between 90 and 100K.

-PB

[ekzotic]

Hi! I Still haven't done a voltage check but I did a bit of testing. Black terminals both show 0 to the ground. I made a jumper wire and connected it to the ground, black terminals and still no readings from the whites.

[ekzotic]

Hi! So I did a voltage check (220v mains) and without 6080 tube:

1   86-87
2   215
3   0
4   215
5   83-84
6   0
7   0
8   0
9   0
10   0
11   0
12   0
13   215
14   0
15   220
20   0
21   222

A1   84
A2   0
A4   0
A5   0
A6   86
A7   0
A9   0

B1   86
B2   215
B3   0
B4   84
B5   215
B6   0
B7   0
B8   0

TRS
TOP   0
MID   0

Tube glows fine (as i think, never used tubes before), diodes glow fine too.

And I opened 6080 tube and it was looking old and rusty, is it fine? Can i clean it somehow?

Thanks for the help!

[Paul Birkeland]

I suspect that your pot is working OK, as the 12AU7 relies on the pot functioning to maintain proper biasing.  Throw the 6080 in and repeat the voltage test.

-PB