[GreenKeys] [OT] - First Tube Equipment Restoration Project

[Ralph Mowery]

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Jeffrey Angus
Sent: Monday, June 10, 2019 10:59 AM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] [OT] - First Tube Equipment Restoration Project

On 6/10/19 9:16 AM, mwillega wrote:
> Do I seek out  or build a tube tester or just test in circuit.
Test in circuit is the easiest.
> Anything else that I should look out for, besides the usual
> concerns about high voltages on the chassis, and old degraded
> components.
1st, find a schematic for it.
2nd, take your time and replace ALL of the electrolytic and
paper capacitors. ONE at a time.

Now you can turn it on and see what it does.

I repair vintage tube radios and test gear, so feel free to
pester me with all your questions.

What model Heathkit scope do you have?

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I agree with Jeff.  Most small tubes do not go bad for a very long time as
long as the filament lights up and they are shiny inside the glass instead
of white.  The burnt looking shiny stuff on the glass is from when the tube
is made.  It is a chemical that is burnt off after the tube is made to burn
out any remaining oxygen  after it is under vacuum.  If very white looking
then oxygen probably has gotten into the tube and it is bad.

Do replace all the electrolytic capacitors.  If it is old enough to have wax
and paper capacitors replace them while you are at it.

Then do a few ohm meter checks to make sure the transformer windings are not
shorted to  ground or each other and the high voltage area B+ is not shorted
to ground.  It should show some high resistance because of the bleeder
resistors.  You may want to do that to start with as some components may be
difficult to come by.  

While it is expensive you may want to spend about $ 15 for a can of Deoxit
to put on  all the switch contacts.

Ralph ku4pt