[Drake] EXT : Fwd: Drake 2B s meter

[Tony Sokol]

Oops!  I Accidentally hit the send button too soon. I wanted to mention that I found the AVC loading problem by pulling tubes until the voltage popped back to normal.  I don't remember for sure but I think it was the Notorious 6U8 which has a bad habit of creating all kinds of problems.
     I did send the original poster a .pdf copy of the updated procedure. Now I will crawl back in my hole and refrain from creating such controversy in the future. :-). 

73 and Merry Christmas to all
Tony -W9JXN



Sent from my iPhone

> On Dec 19, 2014, at 9:35 AM, D C _Mac_ Macdonald <k2gkk at hotmail.com> wrote:
> 
> Any of the Heathkit VTVMs, starting with the venerable V-7 and its various later iterations will also do an equally good job.  They also present a constant 11 Megohm input resistance to the circuit under test.  I still have, even though I don't use it frequently, the large meter version that I built in 1963.  Just remember to take the battery out after using the instrument so that corrosion doesn't set in and ruin your set. 
> 
> * * * * * * * * * * * 
> * 73 - Mac, K2GKK/5 * 
> * (Since 30 Nov 53) * 
> * k2gkk hotmail com * 
> * Oklahoma City, OK * 
> * USAF & FAA (Ret.) * 
> * * * * * * * * * * * 
> 
> 
> 
>> From: william.stevens at ngc.com
>> To: k4oah at mindspring.com; drake at mailman.qth.net
>> Date: Fri, 19 Dec 2014 15:24:29 +0000
>> Subject: Re: [Drake] EXT : Fwd:  Drake 2B s meter
>> 
>> Gary
>> Right on you beat me to it!! Also as with all vintage the published voltage charts were derived using equipment of that era so if you have a good VTVM like an RCA senior volt ohmist that should work but it is usually stated on the voltage and resistance charts the equipment used  or at least it should be. If you can' t find a good vtvm I recommend a fluke 37 or 25, I use both in the shack and at work  you should be able to find them on ebay. Oh and don’t forget that calibration is important for any used test equipment.
>> 73
>> Merry XMAS 
>> Bill
>> WB2UFC
>> 
>> 
>> -----Original Message-----
>> From: Drake [mailto:drake-bounces at mailman.qth.net] On Behalf Of K4OAH
>> Sent: Thursday, December 18, 2014 9:55 PM
>> To: <drake at mailman.qth.net>
>> Subject: EXT :[Drake] Fwd: Drake 2B s meter
>> 
>> 
>> 
>> Sent from my iPad
>> 
>> Begin forwarded message:
>> 
>>> From: K4OAH <k4oah at mindspring.com>
>>> Date: December 18, 2014 at 8:41:29 PM CST
>>> To: Stephanie WX3K <wx3k at ptd.net>
>>> Subject: Re: [Drake] Drake 2B s meter
>>> 
>>> Tony -
>>> 
>>> You are confusing two problems...   Most DMMs can be used for measuring most AVC circuits.  The cheapies, such as the free one from Harbor Freight, are NOT suitable, as they have input impedances in the tens or hundreds of kilohms.  Fluke and other high quality meters have at least an 11 Megohm input impedance, vs the VTVM's 11 Meg 'standard', and may be used for non-RF measurements.
>>> 
>>> I believe what your note is referring to is the measurement of the Grid of a vacuum tube oscillator.  A DMM will 'kill' the oscillator, regardless of how high it's impedance might be.  The problem is the inductive and capacitive loading of the DMM probe and test lead.  The VTVM, on the other hand, has a 10 Megohm input impedance, and a 1 Megohm resistor right at the probe tip to isolate the probe/lead.  Additionally, the distributed capacitance of the shielded lead and it's inductance form a low pass filter to further limit the RF reaching the meter.
>>> 
>>> All tube-type voltage charts I have ever seen were made with a VTVM.
>>> 
>>> By the way, there were three versions of the 2-B, with most of the changes occurring in the AVC area, which accounts for the various Sens voltage readings.
>>> 
>>> 73, Garey - K4OAH
>>> St. Charles, IL
>                         
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