[Boatanchors] newbie question

[J. Forster]

I pretty much agree, with the following proviso:

I'd go for a good, used Tek ANALOG 'scope, like the 453s or 465s. The 475s
and 485s are more failure prone, but have more BW.

Some of the Chinese anolog 'scopes are probably fine.

I would stay away from the hand-held and other digital 'scopes. If you are
unsure of exactly what you are doing, they can easily lie to you because
they are sampling.

And YES, you do need to get probes. Clip leads will not hack it.

YMMV,

-John

============



> OK, John just touched on it. So, let me make my suggestions:
>
> A laboratory grade oscilloscope.
>
> There are in general three grades of instruments;  hobbyist,
> service-man, and laboratory.  At this late date it doesn't make any
> sense to mess with the cheap stuff.  The old lab-grad equipment is
> hardly any more expensive, and feels so much better when you use it.
> Most of it has held up pretty well.
>
> Scopes were not generally in vogue in the vacuum-tube radio era. Either
> they didn't work very well or they were big and expensive (think
> Tektronics 500 series) and would heat the shop.
>
> A scope can do a lot of things that the other basic instruments can't.
> You can wave the probe near a tuning cap and tell if the oscillator is
> running.  Detecting and measuring RF signals is possible. You can even
> guess at the frequency. That means you can signal trace, even without a
> generator if you tune to a station.  It will also substitute for an AC
> or DC analog meter when it's time to peak a circuit.  A pro scope has
> calibrated input attenuators and timebase generators, so you can measure
> voltage and time/freq. fairly accurately.
>
> You can buy a working high-frequency lab-grade scope, like a Tek 465 or
> later 2215 or similar for about a hundred bucks on a good day. They're
> solid state, and most have held up pretty well even after 20-30 years.
> If your chicken, you can get a brand new Chinese scope for a few hundred.
>
> A scope and a DMM, even a cheap one, gets you most of the way there.
> Another overlooked resource is a digital receiver with a BFO,  You can
> use it to set the frequency of a receiver local oscillator to an
> appropriate value, and then align the set accurately on an off-the-air
> signal.
>
> My two cents,
> Al
>
> On 6/30/2013 12:00 PM, J. Forster wrote:
>> I recently came across a similar issue with transistors as I don't
>> currently have access to real a curve tracer. So, I built a primitive
>> one.
>>
>> Just about the same thing can be done to build a simple tube curve
>> tracer.
>> It just takes a transformer with a filament and plate winding, a couple
>> of
>> diodes, and a few resistors, a 9V battery and pot, and a tube socket.
>> The
>> socket can be faked w/ clip leads. Oh, and a 'scope that can do X-Y.
>>
>> Best,
>>
>> -John
>>
>> =================
>>
>>
>>
>>
>>
>>
>>> I agree.  First use the tube tester to rule out a obvious bad tube then
>>> proceed to do the more tedious task of checking other circuit
>>> components.
>>> If after that process you don't find a failure then source replacements
>>> tubes to test the circuit with.
>>>
>>> Tom K3TVC
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Bob Macklin
>>> Sent: Sunday, June 30, 2013 11:38 AM
>>> To: Glen Zook ; Bill Cromwell ; boatanchors at mailman.qth.net
>>> Subject: Re: [Boatanchors] newbie question
>>>
>>> THE PROBLEM I see is getting a stock of replacement tubes. And there is
>>> no
>>> longer a local drug store to run to to buy tubes.
>>>
>>> My position is that for a person that does not have a supply of
>>> replacement
>>> tubes available a tube tester is something to consider.
>>>
>>> In the past 10 years my Heathkit TC-3 has only found one bad tube. But
>>> it
>>> has helped me to determine I did not have a tube problem.
>>>
>>> Bob Macklin
>>> K5MYJ
>>> Seattle, Wa.
>>> "Real Radios Glow In The Dark"
>>>
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>>
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>
> --
> Al Klase - N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
>
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