Bottlehead Forum

Bottlehead Kits => BeePre => Topic started by: ScottAstroNut on February 14, 2021, 07:39:52 PM

Title: BeePre 2 No Sound Either Channel [resolved]
Post by: ScottAstroNut on February 14, 2021, 07:39:52 PM

I just finished the build of the electronics of my new BeePre 2. Upon installing the preamp into my system, I get no sound out of either channel on any of the inputs. I do here an audible "pop" out of both speakers when switching inputs, and on the selected input, I do hear a "swooshing" sound when I adjust the volume pot from at the lowest volume settings.

The BeePre 2 passed all of its resistance and voltage checks along the way, with the possible exception of the last two voltage checks. The voltages on terminals 6 and 16 (the plate voltages, I am assuming?) both measured around 93V. This is about 7% out of the nominal 100V, but I deemed that a "pass." Perhaps I shouldn't have? I switched to a different set of EH 100B tubes, and that didn't make much of a difference.

I've been over the circuit repeatedly and can find no wiring mistakes. I've checked continuity through the input selector switch, and there doesn't appear to be a problem. I can't see a problem with the output wiring, and I've tested for continuity. Looking over all my joints, I can't see any that look like they would be "cold."

Ideas? I can send pictures if you tell me what you want pictures of.

Thanks!

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 03:32:40 AM

Here are some pictures.

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 03:34:02 AM

More pictures.

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 03:34:53 AM

Last set of pics.

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 03:54:47 AM

I built the BeePre 2 according to the instruction manual. Are there any errata that I should have been aware of?

Comparison of my circuit with the schematic shows no deviations that I can find, except perhaps one that may be an error in the schematic? It seems to me that the middle lug of the balance pot shouldn't be directly tied to one of the other lugs of the pot.

Thanks!

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 04:10:12 AM

Looking at the schematic, shouldn't the 130 ohm resistors tie in to the 0.51 ohm resistors at A1 and A4 and B1 and B4?

Title: Re: BeePre 2 No Sound Either Channel
Post by: Tim G. on February 15, 2021, 04:28:46 AM

Interesting, I see that too, it does look like the schematic has those 130ohm connected to the other end of the .51 ohm resistors, but the picture looks like its the other way around in the manual.  Wild theory, are the tubes glowing?  Is it possible the 4 pin socket is installed backwards?  I think voltages would check right, but the heater wouldn't light?

Tim

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 04:44:31 AM

Nope. The 100B's glow nicely.

Title: Re: BeePre 2 No Sound Either Channel
Post by: Thermioniclife on February 15, 2021, 05:03:41 AM

I can't be certain because I do not have a BP2 but it appears that the way the volume control is wired would short the outputs.
Are you sure that the wipers on the pot are wired correctly?

Title: Re: BeePre 2 No Sound Either Channel
Post by: Thermioniclife on February 15, 2021, 05:11:36 AM

I found this picture. Look at the wiring on the volume Pot.

Title: Re: BeePre 2 No Sound Either Channel
Post by: ScottAstroNut on February 15, 2021, 05:31:10 AM

Ah! The sound of sweet music!

That solved it!!!

Boy, does it always help to have a second pair of eyes look over a circuit. I must have checked that pot half a dozen times without seeing my mistake.

Thank you SO VERY MUCH!!!

Title: Re: BeePre 2 No Sound Either Channel
Post by: Thermioniclife on February 15, 2021, 05:35:57 AM

Glad you got it sorted out.