[Drake] Multimeter Suggestions for Drake Service

Tue Dec 7 15:52:18 EST 2010

Jim -

Definitely agree on the digital v. analog scopes.  If you really need to 
carry it around all day and can live with the reduced resolution, they 
serve a purpose, I guess.

The 2465 is a great scope, but has that unobtainium, custom, hybrid IC 
that seems to fail fairly often.  There have been a couple of 
aftermarket attempts to rebuild or replicate it, but I don't know how 
they've progressed.  Unfortunately, without this IC the scope becomes a 
doorstop.

I guess I'll stick with my 465B and 454.  Both cost less than $100, and 
the 465B has been working for 15 years or so for me.  I picked up the 
454 a few years ago from an industrial surplus place, and all it needed 
was a couple of push-on knobs.  They're fast enough for me, and I just 
have to remember that a 50 MHz square wave ain't gonna be square!  :-)

Some of the B&K, Leader and other 'service grade' scopes are adequate, 
but they also make some 'Heathkit grade' models and I don't know enough 
about them to suggest which is which!  You won't go wrong with a Tek scope!

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>

Jim Garland wrote:
> Very good advice, Garey. It's a shame so many hams are unfamiliar with the
> benefits of using a calibrated oscilloscope (and I couldn't agree more about
> your view of most Heathkit oscilloscopes). With a good scope, one actually
> doesn't need _any_ other voltage measuring instruments.
>
> The only thing I'd add to your comments is that, for most ham use, an analog
> scope is preferred over a digital scope. Prices have really come down on
> excellent analog oscilloscopes in the past few years. In the opinion of
> many, the very best analog scope ever made was the Tektronix 2465B, and one
> can pick up one in excellent condition for about $400 (new cost was about
> $10K). Lesser scopes (which are perfectly appropriate for 99% of ham use)
> cost proportionately less.  Over the weekend, a ham buddy brought over a B&K
> 40MHz scope that he bought for $15 at a hamfest. A few spritzes of DeOxit on
> the rotary switches and it worked just fine, with excellent calibration and
> very stable triggering.
> 73,
> Jim W8ZR
>
>    
>> -----Original Message-----
>> From: drake-bounces at mailman.qth.net [mailto:drake-bounces at mailman.qth.net]
>>      
> On
>    
>> Behalf Of Garey Barrell
>> Sent: Tuesday, December 07, 2010 12:51 PM
>> To: Drake
>> Subject: Re: [Drake] Multimeter Suggestions for Drake Service
>>
>> Richard -
>>
>> The key to the multimeter is input impedance.  Ultra-precise voltage
>> readings are never really required to service our gear.  Aside from
>> Collins or other government supported manufacturers, most repair and
>> even design work of Ham gear was done with Heathkit class VTVMs.  Every
>> once in a while someone would spring for an RCA VoltOhmyst, but not
>> often!  As for reading voltages to two (or three!) decimal places, I
>> can't think of a single place where that is necessary.  The only thing
>> that comes close is the Drake receiver Sensitivity or AVC threshold
>> specified as -1.35 VDC, and it tends to wander a couple of tenths over
>> temperature, etc., so not REALLY all that tight.
>>
>> The Heathkit IM-11 / IM-18 etc., are perfectly suited.  The better
>> commercial equipment such as the HP 427 VTVM and up is great, and
>> certainly built to a higher standard.  Some of the HP meters had
>> individually printed meter scales for improved accuracy.  They are nicer
>> mechanically, are a pleasure to use, and many have come down to a
>> reasonable price since just about all commercial test is computer
>> controlled these days.  But for our use, there really isn't anything
>> better than an IM-18 from a FUNCTIONAL standpoint.
>>
>> My second purchase would be a scope.  Here the opposite is true.  All
>> but one, or maybe two, of the Heathkit scopes aren't worth the trouble
>> to carry them home.  For a scope to be useful, it really needs to be
>> 'calibrated', both in time and amplitude, and have 'triggered sweep'.
>> Anything else is a frustrating waste of time and energy for anything
>> beyond Lissajous or sine wave displays.  They do make good SSB
>> modulation monitors with modification, but as a lab scope, no thank
>> you.  Here you want to find a good used Tektronix 2215A, 465B, 454A,
>> etc. unit.  You can get any one of them for $100-150 if you're patient.
>> The surplus labs that refurb and calibrate them to NBS standards cost
>> quite a bit more, but they all show up from time to time on the usual
>> places at very reasonable prices.  With a good scope, you'll find you
>> reach for it FIRST about 90% of the time.  (Remember, it's 'calibrated'
>> and with a single touch of a probe you can not only tell if a power
>> supply is working and the correct voltage, you can also see just how
>> much ripple is present.)
>>
>> After the scope, I'd get one of the NORCAL or Elecraft signal
>> generators.  They're about the size of an Altoids tin or smaller, and
>> generate a calibrated 1 uV and 50 uV signal on a single, crystal
>> controlled frequency on the 80, 40, 30 and 20M bands.  The Elecraft is
>> only 80, 40 and 20M.  This is all the signal generator you need for
>> testing, repairing and even calibrating S-Meters on our stuff, at least
>> on those three or four bands.  Wide range, continuous coverage,
>> calibrated signal generators are nice, but you'll find that you don't
>> use them often.  In a pinch you can always use your modern transceiver
>> as a source.  The receiver portion of it also makes a fair spectrum
>> analyzer or signal tracer.
>>
>> Lastly, I'd invest in one GOOD Fluke DMM to use as a reference source
>> for calibration of all the above.  Take care of it and keep it in a safe
>> place.  If you want/need a DMM for the car or yard or on the bench, the
>> little Harbor Freight $2-3 meters are ok with one caveat.  They have a
>> LOW input impedance (~1 Meg) which will mislead you on some tube grid,
>> AVC, or other high impedance circuits.  The VTVM is 11 Meg, and is
>> hardly ever a loading risk.  A good scope probe (10x) is also 10 Meg.
>>
>> Beyond this you're looking at convenience, preference, and how much
>> money you want to spend.  But if you have the above, you'll be able to
>> do just about anything you need to do!
>>
>> 73, Garey - K4OAH
>> Glen Allen, VA
>>
>> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
>> and TR-4/C Service Supplement CDs
>> <www.k4oah.com>
>>
>>
>> Richard Bell wrote:
>>      
>>> I know we've been down this path before, but I don't seem to remember
>>>        
> the answer.
>    
>>> What would be a good multimeter to be used for servicing our beloved
>>>        
> Drake gear?
>    
>>> I know some with say a old school VTVM from Heahkit.  Others will say
>>>        
> buy a Fluke.
>    
>>> I'm trying to get the retirement test gear in order before I have no
>>>        
> funds for this sort of
>    
>> journey.
>>      
>>> Feel free to email me off the list, richfbell at sbcglobal.net, if you
>>>        
> desire.
>    
>>> TNX&   73 W5BXE
>>>
>>>
>>>        
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