Testing with tubes terminal 7 read 1vdc instead of 170-230

[DPetrini]

Hi all, any idea where to look for? Apparently all seems done right at First slight. Thanxs

PS Yellow film Is kapton insulating film as could not find the original insulator i might Lost

[Paul Birkeland]

Can we see the bottom of the PC board and the socket wiring?

[DPetrini]

Sure, thanxs

[Paul Birkeland]

What is your resistance to ground on terminal 7?  Does that red wire touch pins 8/9 on the tube socket?  If it does, that will give you very low voltage on terminal 7.

[DPetrini]

Hi Paul, do you want I Measure the resistance between 7 and 8 with tubes and power on or not? Better double check before making disasters.  I trieds now with no power and no tubes and read 4Mohm and the value continue to increase.

About the cable, i haved distanced the Red cable. After the change still read same voltage(0.961VDC). I can locally order the 4 transistors and i might replace all 4 Just to be sure. Unless other indications from you. Thanxs

[Paul Birkeland]

Now it looks like pins 1 and 2 on that 9 pin socket shown are touching.

I would not replace the transistors, as an issue like this is the output of the C4S being pulled down below any voltage present on any pins of any of those transistors, so it's likely external to the C4S board.  You can check this by rotating the board 180 degrees and reinstalling it, then see if the low voltage moves to another terminal or stays where it is.

[DPetrini]

I settled the proximity detected by you. Swopped 180 and remeasured . No way both 7 and 14 have same Reading 0.973 and 0.975 on 14.

[Paul Birkeland]

I would reflow the solder joints on each MJE5731A.

[DPetrini]

Ok Will do later today when back to home.

[DPetrini]

Done It. Used the desoldering gun to make a clean work. Resoldered with my best ...Shining tin Yes.. all...no way ..still 0.9 etcetc.

What can i check else?

[Paul Birkeland]

Remove the wires from OA and OB, turn the amp on, then measure the voltages at OA and OB.

[DPetrini]

Tubes in or out?

[Paul Birkeland]

It won't matter for this test.

[DPetrini]

If you meant to measure from point8 and Oa and from point 8 to OB ,see picture, i have 2mV at start that goes to 0mV in few seconds.

[Paul Birkeland]

Measure voltage from amp ground to OA, and amp ground to OB.