Bottlehead Forum

Bottlehead Kits => BeePre => Topic started by: bombay317 on June 30, 2024, 04:24:07 AM

Title: BeePre2 300B Preamplifier Kit with all Upgrades Stopped Working after 2 Years
Post by: bombay317 on June 30, 2024, 04:24:07 AM

The other day my BeePre2 was working, today it is not.  Not sure if really anything was different.  It is no sound out of either channel.  It has been working since I built it about two years ago.

I tried the voltage checks on all three manuals and get some weird values. Help?

BeePre2 Manual:

Pg 34:
Set your DMM to DC volts in the appropriate range (300 or higher). Insert the red probe to 31L and the black probe to 33L. These probes need to push the unsoldered resistor leads into contact with their terminals. Make sure that the metal ends of the two test leads to not touch each other. Plug the power cable into the wall. You should read 250VDC ±20%.  I read 265VDC when I completed the kit, and now 252.6VDC.

Pg 39: (both at 6.3VDC)

Pg 41: (tube glow passes)

Pg 55:

Measure the voltage at terminal 6. It should be close to 100VDC. I measure 151VDC.
Measure the voltage at terminal 16. It should be close to 100VDC. I measure 143.8VDC

BeePre Output Upgrade:

Pg 34:

Measure the voltage at terminals 45 and 60. It should be approximately 6.5VDC. 6.66VDC and 6.69VDC
Measure the voltage on each kReg position. It should be between 7-10VDC. 8.9VDC and 9.34VDC
Measure the voltage at terminals 46 and 51. It should be approximately 183VDC. 180.6VDC / 182.6VDC

BeeTwoQuiet

Pg 19:

Measure the votage at terminals 1 and 11. It should be approximately 150VDC. 218VDC / 217VDC
Measure the votage at terminals 6 and 16. It should be between 95-125VDC. 149VDC / 141VDC

Title: Re: BeePre2 300B Preamplifier Kit with all Upgrades Stopped Working after 2 Years
Post by: Paul Birkeland on June 30, 2024, 05:54:59 AM

Quote from: bombay317 on June 30, 2024, 04:24:07 AM

Measure the voltage at terminal 6. It should be close to 100VDC. I measure 151VDC.
Measure the voltage at terminal 16. It should be close to 100VDC. I measure 143.8VDC

Neither 300B appears to be properly conducting.  While the immediate panic-level response would be to replace the 300Bs, I wouldn't do that.  I suspect that you have a ground wire between the power supply and the circuit that's either poorly soldered or has broken loose, and that is preventing some or all of the circuit from working properly. 

Title: Re: BeePre2 300B Preamplifier Kit with all Upgrades Stopped Working after 2 Years
Post by: bombay317 on June 30, 2024, 09:46:17 AM

I did have a spare of 300Bs that I tried to see if they worked, same thing happened.  So now I might have 4 300Bs that are toast.

I'll go through the grounds and check.

Title: Re: BeePre2 300B Preamplifier Kit with all Upgrades Stopped Working after 2 Years
Post by: Paul Birkeland on June 30, 2024, 10:06:35 AM

Quote from: bombay317 on June 30, 2024, 09:46:17 AM

So now I might have 4 300Bs that are toast.

No, you don't.  There's a broken wire or a bad solder joint not allowing things to work properly.