BeePre completed

[RPMac]

Got my BeePre completed. Resistance check was spot on...voltage check was within spec except
Terminal 1 was 3.4v should be 5v
Terminal 4 was 10.1v should be 9.85v

B side
Terminal 16 5.16v
Terminal 19 9.84v

So I put in the system to get some run time on it before checking voltages again. Turn on has a big thump from the subs, but sound was fine. Put about 6 hours on first day.

After playing several hours the second day, I decided to try some Upscale Audio Chinese made mesh plates. At turn on, there was a crackling buzz in the B side. I put on the music and it sounded normal. Then the buzzing side reduced volume, then nothing. Before I got to the amps, the other side lost volume.

I pulled the mesh tubes thinking I had fried them, but when I put them in my Parabee, the worked, but seemed to come on slower than normal.

Back to the BeePre...I put the EH 300Bs back in and thing seemed normal. 300B in, 300b out...sweet!

This morning when I turned on, the crackling buzz returned in the B side with the EH 300B. I swapped tubes and the buzz followed the tube...then got quieter and went away. Playing now with out issue.

When I get the chance, I will take it back to the shop to take resistance and voltage checks.
Any terminals I should pay particular attention to?

I also want to do checks with the different 300B tubes...any I shouldn't try besides the Upscale Audio tubes?

JJ
Sophia mesh
EH
Upscale Audio

[RPMac]

So much for that, the B side made a loud popping and went quiet.

[Grainger49]

Robert,

FAQ #1 in this thread:    http://www.bottlehead.com/smf/index.php/topic,2408.0.html

Turn on and turn off thumps are normal.  Just follow the instructions and you are good to go.

[RPMac]

Put the FP III back in and the Parabees are playing.

The EH on the B side only has half the filament lighting. This has always been the case.

Grainger, I understand, it was that the thump is louder than with the FP III. Trying to give as much info as possible because I don't know what is important. Thanks.

I am going out for the day, will make measurements when I get back. I will leave the tubes as they are when I measure.

[Paul Birkeland]

The EH on the B side only has half the filament lighting. This has always been the case.

That is very likely a tube failure.  You can measure the DC voltage across the 0.62 Ohm resistor on the filament regulator board with the tubes installed.  A good 300B should make  0.77V across this resistor.

FWIW, I bought some Guiguang 300B's to try out in the BeePre.  They have been mostly quiet, with periods of making random, spurious noises here and there. 

[RPMac]

Paul,

Across the .62 Ohm resister...

A tube .77V ; plate 120V ; ter.1 5.2V ; ter.4 9.8V

B tube .49V ; plate 110V ; ter.16 3.4V ; ter.19 10.1V

I quess I'll try the JJ 300B

[RPMac]

The JJs check out .78V across the .62 on both.
5.3V and 9.8V on either side of both filaments
99.7V and 101.6 on the plates
C7--146V  C3--4.4V
D7--145V  D3--4.2V

Music sounding GREAT!!!!

[Paul Joppa]

Looks like the bad tube has the two filament halves in parallel. When one went out, the other by itself has a higher resistance and is hogging the voltage. You are then running 6.7 on the working half filament, which is designed for 5 volts - it will blow out very quickly under those conditions.

[RPMac]

Listening this morning and I have a buzz that comes and goes away. It is in both sides, doesn't change with balance or volume other than the music covers it. The only common component is the power cord in the beepre.
Any ideas?

[johnsonad]

Tubes.  Burn them in hard for a couple of days and more than likely it will go away. 

[RPMac]

Aaron, the JJ's I'm using now have many hours on them when in my parabee's.

The reason I bring up the buzz and big turn-on thump is because I haven't had them before.
I think I answered the buzz issue in my post being the power cord is the only common component...probably picking up something from the house wiring. I do use balanced power at +61/-61 if that matters.

On the big thump, the FP III has a 1000 Ohm resister between the signal outputs. I wonder if I put a resister ahead of the sub output, if that would help?

The more break-in time this BeePre has, the better it sounds. Going to have to hook it back to my 3B7 Stereomour to have an all DHT Bottlehead system.