Try using an old glass type 2C39 in a cavity amp for 23cms and you get similar
results
when pushed hard. A nice clean hole with no apparent other damage.
John ZS5JF
----------
> From: Doug Person <w4dxv@ibm.net>
> To: Dick Green <dick.green@valley.net>; amps <amps@contesting.com>
> Subject: Re: [AMPS] Finally - a real amp
To: <amps@contesting.com>
> Date: 11 June 1999 08:12
>
>
> Hi Dick,
>
> Thanks for your response. I was tuning the amp on and off about 10 seconds
> at a time. It seemed to tune up fine - then bang and no ip or ig on the
> meter. The crazy part is, you would think were ever that arc came from
> would have at least carbon trails or some fusing - but nothing! The hole is
> pointing right at the plate RF coke, but not even any discoloration is
> noticeable. I ordered a new plate RF choke from Ameritron anyway - due to
> previous comments about the original being somewhat resonant near 17 meters.
>
> The hole in the tube is remarkable. I've been haming for 38 years and I've
> seen cracked glass before but not a hole with flowing glass!
>
> Doug -- W4DXV
>
>
> ----- Original Message -----
> From: Dick Green <dick.green@valley.net>
> To: Doug Person <w4dxv@ibm.net>; amps <amps@contesting.com>
> Sent: Friday, June 11, 1999 12:53 PM
> Subject: Re: [AMPS] Finally - a real amp
>
>
> >
> > > Now that I've gotton your input, I'm sorry to report that while tuning
> > > the AL-80A on 17 meters with 500ma ip and 150 ma of ig, A somewhat loud
> > and
> > > most unpleasant noise ocurred within the amp after which there was no
> > current
> > > indicated for either ig or ip. Did I fry the tube?
> >
> > That's too much plate and grid current. About how long was the amp
> key-down
> > before the bang occured?
> >
> > > Instead, when I
> > > removed the 3-500z, I first noticed the top inside surface of the glass
> > had
> > > a powdery substance on it in pattern not unlike the fins. Then I
> > discovery
> > > the really interesting new characteristic of the tube. There was a hole
> > > clear through the glass as though it had been shot by a high-powered
> > laser.
> > > There are fine cracks around the hole and the glass had actually flowed
> > > inward almost half an inch. Wow. Watch out for 17 meters on this baby.
> >
> > I'd be interested in hearing the group's theories on exactly what happened
> > here. Flowing glass? That must take a lot of heat! I can see where the RF
> > choke would be destroyed if it had a resonance at 17M, but isn't it more
> > likely that the tube was destroyed by the excess plate current and/or grid
> > current?
> >
> > Doug, if I were you I would thoroughly check that amp before installing a
> > new tube (BE CAREFUL -- HV CAN KILL YOU!) The heavy current drawn during
> > this event might have damaged other components. In particular, I would
> check
> > the plate RF choke, parasitic suppressor resistor, HV power supply,
> fuse(s),
> > filament transformer, bias diode, meter resistors, meters, etc. It would
> be
> > wise to enlist the help of someone experienced in troubleshooting 3-500Z
> > amps.
> >
> > 73, Dick WC1M
> >
> >
> >
> > --
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> >
> >
>
>
> --
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