News: Trouble logging in? Log in from the login page.
August 21, 2019, 04:48:47 AM

Author Topic: Simple 300B Test?  (Read 642 times)

0 Members and 1 Guest are viewing this topic.

Offline Gerry E.

  • Full Member
  • ***
  • Posts: 158
Simple 300B Test?
« on: August 18, 2018, 05:58:11 AM »
Hi:

I have early Paramounts with the v1.1 soft start upgrade kit installed.  Is there a simple way to make sure that the voltages to the 300B tubes are in the ballpark?  Preferably from the top without the 300Bs installed?  I have a meter and know the safety rules from the manuals.  Thanks!

Gerry

Online Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 11131
Re: Simple 300B Test?
« Reply #1 on: August 18, 2018, 06:09:46 AM »
From the top, not so much.  Performing the voltage checks on the 4 pin socket will give you some data on how the 300B is operating, though it will look really solid until it's almost completely dead.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline johnsonad

  • Hero Member
  • *****
  • Posts: 1376
Re: Simple 300B Test?
« Reply #2 on: August 18, 2018, 11:16:09 AM »
Gerry,

Flip the top plate over and elevate the base on something. I use books at the corner. Put the grounding plug in and measure away, safely. I do this from time to time.

Aaron
Aaron Johnson

Offline Gerry E.

  • Full Member
  • ***
  • Posts: 158
Re: Simple 300B Test?
« Reply #3 on: August 21, 2018, 02:28:48 AM »
Thanks PB and Aaron!  Your replies were the little push I needed to do it the right way.  I measured one of the amps yesterday and the results were very close to the manual numbers (manual / my results):

A1      74.1V     74.3V
A2      428V      427V
A3          0*     14mV
A4      69.2      69.3V

* Close to zero

I'll measure the 2nd amp in the next day or two.

Gerry

Offline johnsonad

  • Hero Member
  • *****
  • Posts: 1376
Re: Simple 300B Test?
« Reply #4 on: August 21, 2018, 04:04:30 PM »
I was an early Elrog user and had one of the tubes die on me. It took out the cathode resistor along with it. Now, PB reminded me that my choice of cathode resistors was questionable and it most likely was the other way around.  They sounded great up until then. Periodic testing is easy to do and gives you the reassurance that you’re not smoking those expensive 300B’s.  It’s very easy with those large four pin sockets too!
« Last Edit: August 21, 2018, 04:34:38 PM by johnsonad »
Aaron Johnson

Offline Gerry E.

  • Full Member
  • ***
  • Posts: 158
Re: Simple 300B Test?
« Reply #5 on: August 23, 2018, 08:32:32 AM »
Hi Aaron:

One of my Elrog 300Bs died on me too.  The other one tests low.  I thought about buying a newer pair because they are supposedly more reliable/robust but in the end didn't want to get burned again (pun intended).  Too bad because I thought they were the best sounding 300Bs I have ever heard.  Even a bit better sounding than my 1998 re-issue WE 300Bs. 

I just sold those 1998 WE 300Bs with an eye towards buying a new pair of WE 300Bs when they are released this fall.  I wouldn't have sold the old pair if I wasn't 100% convinced that the new ones are coming back soon.

Back to the original topic of this thread, I just measured the 2nd amp and while the results were good, not quite as close to the manual numbers as the first amp (manual numbers / my results):
 

             
A1      74.1V     75.1V
A2      428V      426V
A3          0*      91mV
A4      69.2V     70.2V

*Close to zero

A3 was interesting.  It started at 55mV and as the amp warmed up, it rose to a high of 91mV.  I measured it one last time and the result was 86mV.  I know this is a very low number and not anything to worry about, correct?  Thanks!

Gerry

Online Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 11131
Re: Simple 300B Test?
« Reply #6 on: August 23, 2018, 09:55:25 AM »
Those are still healthy numbers.

Are you using the stock coupling caps? 

~100mV isn't particularly concerning but still probably something to measure again in 6-12 months.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline faskenite

  • Jr. Member
  • **
  • Posts: 42
Re: Simple 300B Test?
« Reply #7 on: August 23, 2018, 09:55:59 AM »
What's this about WE 300B's being brought to market this fall?  Is the information reliable?

Offline Gerry E.

  • Full Member
  • ***
  • Posts: 158
Re: Simple 300B Test?
« Reply #8 on: August 24, 2018, 02:36:14 AM »

Are you using the stock coupling caps?  ~100mV isn't particularly concerning but still probably something to measure again in 6-12 months.


PB - Thanks for answering my question.  See the attached photo to answer your question.   

Faskenite - Yes, very reliable information.  These two links will provide all the information you need:

http://www.westernelectric.com/news/the-return.html

https://www.facebook.com/WesternElectric/

Gerry

   

 

Offline faskenite

  • Jr. Member
  • **
  • Posts: 42
Re: Simple 300B Test?
« Reply #9 on: August 24, 2018, 03:41:44 AM »
Thanks for the links Gerry.  There have been a few false alarms over the years.  During which my 1998 WE’s have continued to work just fine!