BeePre Voltage Check Fail [resolved]

galyons · 934

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Offline galyons

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on: August 06, 2022, 03:06:54 PM
My BeePre has performed marvelously for years now,  But today it just did not sound right.  So I did a voltage check. Everything was within spec, except for one C4S board. All the LED's are glowing on the C4S board.  There are no visibly burned resistors.  But I am getting off voltages on the board:
T16 3.2VDC v. 5VDC 
T17 116.6VDC v. 90-110VDC
T19 10.16VDC v. 9.86VDC

So it looks like I have lost the magic smoke somewhere.  The Smash is filling in, but...

Thoughts to resolve?

Cheers,
Geary
« Last Edit: August 08, 2022, 04:54:19 AM by Paul Birkeland »

VPI TNT IV/JMW 3D 12+Benz LP-S>  Eros + Auralic Aries + ANK Dac 4.1 >Eros TH+ Otari MX5050 IIIB2 > BeePre >Paramount 300B 7N7 > EV Sentry IV-A

Thorens TD124/Ortofon RMG-212/SPU >Seduction > Smash^Up> Paramour 45 MQ >K12's


Offline Paul Birkeland

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Reply #1 on: August 06, 2022, 04:21:44 PM
The 3.2V is an oddball, what is POS OUT on that side of the preamp?  I suspect that is your 10.16V, and that in combination with the low 3.2V is the root of the problem.  Does this set of voltages happen to follow a tube?  The high voltage at T19 tends to suggest that the 300B on that side is not drawing a lot in the way of current, and this is confirmed by the low bias voltage at T16.  If these voltages are not dependent on a particular 300B, there's likely a loose solder joint at work preventing the filament from drawing appropriate current.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline galyons

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Reply #2 on: August 06, 2022, 06:05:41 PM
  :-[  The good news is it is NOT a bad solder joint!  The bad news is that it is, in fact, the 300B. I should have thought to swap sides! I was just shocked, as the BeePre has been pretty faultless!  Known pair of 300B's in and making beautiful music!! 

Thanks PB for the rapid and correct diagnosis!! 

Cheers,
Geary

VPI TNT IV/JMW 3D 12+Benz LP-S>  Eros + Auralic Aries + ANK Dac 4.1 >Eros TH+ Otari MX5050 IIIB2 > BeePre >Paramount 300B 7N7 > EV Sentry IV-A

Thorens TD124/Ortofon RMG-212/SPU >Seduction > Smash^Up> Paramour 45 MQ >K12's