I may shortly be looking to purchase a variac.
After building a dim bulb tester this weekend I have a minor update.
With 120V connected, the HV primary disconnected and one tube in a socket
(doesn’t matter which I use) the 100W bulb in my tester lights up bright. No
fan and the meter lights aren’t on. If I take out the tube the fan and meter
lights work. So I guess I have a shorted tube? Would it be good to double check
the DC/AC voltage on the filament supply with the tubes plugged in? That would
show any sags that might exist.
-Warren
> On Jul 7, 2017, at 12:58 PM, gudguyham--- via Amps <amps@contesting.com>
> wrote:
>
> I know I sound like a broken record but yes, a Variac is the way to go.
> Especially with amps that can have power supply problems and gassy tubes.
> You will hear the plate transformer groan and won't see HV climbing on the
> meter if there is a problem in the PS long before the smoke Genie appears.
> My Variac gets used daily several times after doing ANY work on an amp. It's
> saved me loads of time fixing blown parts that would normally occur if I had
> just turned an amp on with problems. Best investment I ever made. 0-250
> volts at 20 amps.
>
> Sent from AOL Mobile Mail
>
>
> -----Original Message-----
> From: Bill Turner <dezrat@outlook.com>
> To: Amps group <amps@contesting.com>
> Sent: Fri, Jul 7, 2017 12:34 PM
> Subject: Re: [Amps] SB220 step start blows fuses
>
>
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>
> On Fri, 7 Jul 2017 10:21:36 -0400, Mark B. wrote:
>
>> A variac varies voltage. It is not designed to limit current.
>
> REPLY:
>
> At the very low end of its range, a Variac limits current just fine. I
> worked as a calibration technician at Tektronix for years, taking
> brand new scopes off the assembly line and powering them up for the
> first time. Believe me, a Variac is the only way to go with a unit
> which could have any number of problems at first. Over the years I
> powered up literally thousands of scopes this way and never a problem
> with current limiting.
>
> 73, Bill W6WRT
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