small circuit board OB=0v

[muniforever]

Hello! first time builder here. I recently completed the base level Crack with wonderful results. today while installing the 1st circuit board upgrade, I got a reading of 0v for OB point. all my voltage readings are as follows:

OA = 70
IA = 189
B-A/B = 0
IB = 189
OB = 0v

I reheated center pin of MJE-350, still reads 0v.

both right LED are not lit, including lower LED connecting A3. all LED are oriented properly


Thank you all for your help!

 

[Paul Birkeland]

Can you post some build photos?

 

[muniforever]

Here's a few, any certain connections need to be shown?

 

[Paul Birkeland]

If your iron has temperature adjustment, I would turn it all the way up and reheat all of the solder joints on that board other than the ones for the LEDs.

 

[muniforever]

All points have been checked and reheated on the board, still at -0v

 

[Paul Birkeland]

Can you unscrew the screws holding the board down, tilt it up, then post a photo of the bottom?

 

[Thermioniclife]

The led at A3 looks like it's not soldered Cant help with Ob.

 

[muniforever]

A3 is soldered properly it seems, no pins touching in A or B. The amp passed all tests as a base crack and worked flawlessly for 2 weeks before I started this process, but I'm thinking I may want to do a full voltage test again? This one is stumping me.

 

[Paul Birkeland]

A hotter iron would definitely help flow those joints out a bit.

 

[muniforever]

After reheating all joints at full temp with yihua 939D+ soldering station and checking voltage with a new ideal 61-327 multimeter, OB is measuring -1.4v on 400dc mode.

 

[Paul Birkeland]

If you rotate the board 180 degrees and wire it back in does the 0V follow the side of the board or the terminals on the amp? (Feed OA to terminal 5, IA to 4, IB to 2, OB to 1)

 

[muniforever]

A1 I'm getting -1.4v as well as on B4 if that helps, but I'll try flipping board orientation 180 and I'll get back to you.

 

[muniforever]

Good day! Thank you for helping me with this process, I really appreciate it. I just flipped the board orientation 180°, and the problem followed that side of the board over to 1st terminal. Faulty JME-350 on that side, perhaps?

 

[Paul Birkeland]

Faulty transistors typically fail short, so you wouldn't see 0V.  You could very carefully apply just a little more heat to the LED solder joints as well just to be sure they are well soldered as well.

 

[muniforever]

Reheated led connections carefully, still at -1.4v.

 

[Paul Birkeland]

Well, you can e-mail replacementparts(at)bottlehead(dot)com and request a new small board and parts to stuff it. 

 

[muniforever]

Thank you Paul, you've been a huge help to an amateur! I will email for a replacement shortly.

-Sean Webster