Page 55 voltage check wrong need help again.

[Kurthaudio]

Hello again,

Short version:
#14 to 30: 9.6vdc

14 to 16: 87vdc

14 to 11: 175vdc



14 to 25: 0.9vdc

14 to 6: 45vdc

14 to 1: 175vdc

Some of the parts look different then stock. That’s because they have been soldered and desoldered to many times so I replaced them with equal values of what I have laying around.

I switched the tubes and the voltages stay exactly the same. I switched out the 100k pot again exact same voltages. If I disconnect the b+ voltage wires I get 260vdc as soon as I connect them it drops to 175?

This kit is kicking my but and once again I’m at a loss………

 

[Kurthaudio]

Here is a pic

 

[Paul Birkeland]

You need more heat on those solder joints, most of them look pretty cold.

 

[Kurthaudio]

I can assure you they are not cold joints it’s Mundorf supreme diver gold solder and that’s just how it looks.

I do have several hounds that are not soldered until I get this voltage issue sorted

 

[Kurthaudio]

Any other help?

 

[Thermioniclife]

I'm certain that 12 and 14 are cold. Balance control and the adjacent terminal strip look to have no solder, just solder them and don't worry about getting the voltage problem solved. How do you know that the unsoldered joints are not causing the problem?

 

[Kurthaudio]

I know because I had this problem while everything was soldered. 14 and 11 are not soldered thats why they look like they are cold joints.

When I changed the balance pot I ran new wires and did not solder them. I wanted to leave them until I found out why I’m having this issue. To keep this from getting confused I’ll solder everything up take new readings and report back.

 

[Thermioniclife]

Holy smokes, there is an awful lot of silver in this solder 9.5%

 

[Kurthaudio]

Ok guys, I soldered everything up. I’m still getting the same voltages as posted in my first post.

B seems ok with 14 - 30: 9.6vdc and 14 to 16: 87vdc

A seems to be my problem. I’m getting 14- 25:.9vdc and 14- 6: 45vdc.

Is it normal to be getting 175vdc @ 11 and 14?

 

[Kurthaudio]

Lol solders like it too 

 

[Thermioniclife]

Not having a beepre 2 I can't be certain but it looks like 11 is getting the b+ to the plate and 14 is ground. S measuring between 11 and 14 could show 175vdc. What voltage do you get on the equivalent terminals on the other tube?
/

 

[Kurthaudio]

Yes you are correct 11 is B+ and 14 is negative

The solder tabs are basically just a junction that routs wires down to 1 and 4 of the A socket. I’m getting 175vdc at both 11 to 14 and 4 to 1

Earlier in the build the instructions ask for voltage check of the B+ power supply before it’s connected to anything and I get 260vdc. (250 +/- 20%)

It seems odd to me that once connected it drops to 175vdc?.?. Shouldnt it remain 260vdc?

 

[Thermioniclife]

No i'ts not funny, that's the plate voltage at the operating point. If you pull the tubes out the b
+ will jump back to about 260vdc. You have a voltage drop of around 45vdc due to the cathode resistor. No worries, march on soldier.

 

[Kurthaudio]

Ok. Thank you clearing that up.

But how in the world am I only getting 45 volts at 6? And only .9vdc at 25? I do have 175@ 1.

 

[Thermioniclife]

As I stated earlier, I do not have a Beepre 2 or the schematics. My advise is follow the instructions, solder when told to do so, and preform any resistance and voltage tests when directed to do so. And then if any problems turn up than that's when to ask questions.

 

[Kurthaudio]

That’s what I’m doing, I’m at the point where I should be getting 10vdc and 100vdc and I’m only getting 0.9vdc and 45vdc. I cant get past this thats why I am asking for help right now.

 

[Kurthaudio]

That’s exactly what I’m doing.

I should be getting 10vdc and 100vdc on 25 and 6 respectively

I’m getting 0.9vdc and 45vdc……that is what this thread is all about. I’m asking for help to figure this out.

 

[Thermioniclife]

I'm sure either PB or PJ or if you are lucky PB&J will chime in and get you sorted out. I did about all I can do without being familiar of that product. Don't get to stressed out, you'll be fine in the end.

 

[Kurthaudio]

Thanks brother. I needed to hear that. I am getting a bit stressed about this. Lol. Thank you for your help. I did learn a little.

 

[Paul Birkeland]

A seems to be my problem. I’m getting 14- 25:.9vdc and 14- 6: 45vdc.

This needs to be cleared up before you continue.  There could be a loose connection at pin 3 on that socket which isn't providing the grid with a solid reference to ground.

It's also possible to plug the 300B into the socket with the fat pins not in the bigger holes, though it takes some force to do that.  If this is done, you can get weird voltages. 

It's going to be tough to provide much more assistance beyond that, as all the parts in this preamp are not the parts we provided, so there isn't much of a way to visually compare.