[R-390] Tube Testers

Tue Sep 17 19:54:53 EDT 2013

Yep and that was back in the 70’s when tubes were young.  Now days many of the tubes I use are really old NOS or in many cases pulls from other stuff over the years.  I’m not fond of shoving a tube with a potential short into a radio without checking it before it goes in on something that won’t go up in smoke and cause me grief.  The tube tester is good for that...weeding out gassy and shorted tubes...sometimes NOS tubes that have been banged around for years now.

While I agree the radio is the best thing for evaluating performance of a handful of tubes once they have passed the gas and shorts test..there is still a purpose for a decent tube tester.

That said I check caps and resistors on the appropriate testers prior to placing them in the circuit too...and they are all new components.

Just a piece of mind thing I guess...

Also commercial radio shops were run on a shoestring too..  Had a friend that owned one...there was no money to be made in that business...most of the test gear was really old as was the vehicles they ran around in.  My shop is equipped better than most Motorola or GE service shops I’ve been in.

Cecil

K5DL

From: KR4HV
Sent: ‎September‎ ‎17‎, ‎2013 ‎11‎:‎50‎ ‎AM
To: 'KA9EGW'; R-390 at mailman.qth.net
Subject: Re: [R-390] Tube Testers

FWIW, during the early (1970's) part of my long association with and when I
worked for Motorola in their two-way radio division, we still maintained a
LOT of tube sets.  I never went in a Motorola shop and saw a tube tester.
New tubes were always put in the radio under test and testset meter
readings, signal generator settings and other parameters observed to
determine if a tube was operating to spec.  Never, ever was a tube tester
used or even present in the maintenance shops. 

When new I once asked where the tube tester was and I was told that "TV
repair guys" used them because they didn't stock many spares and besides,
testers weren't conclusive.  We always had several new tubes of each type to
try.

IMHO, It's best to spend your money on a set or two of running spares to
have on hand.  Most likely you'll need a few over the years anyway since the
R-300/390A disease is usually severe and generally lasts a long time.

Regards,
Walt
KR4HV

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of KA9EGW
Sent: Tuesday, September 17, 2013 11:29 AM
To: R-390 at mailman.qth.net
Subject: Re: [R-390] Tube Testers

What he said.
73, Brian KA9EGW

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Glenn Little WB4UIV
Sent: Tuesday, September 17, 2013 1:13 AM
To: R-390 at mailman.qth.net
Subject: Re: [R-390] Tube Testers

Your best tube tester is the instrument that you will be using the tube in.
If it works in the circuit, it is good.
Measure the voltages around the tube.
If they vary significantly from the manual, replace the tube.
If this fixes the problem, the tube was bad.
If the problem remains, put the original tube back in and find the bad
capacitor, open coil or out of tolerance resistor.
Most of the resistors will be out of tolerance, high.
Any paper capacitors should be replaced with mylar or similar capacitors.
By definition, the paper capacitors are bad.

73
Glenn
WB4UIV

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