It does not take a "bad tube", it only takes a tube that is low in
emission to throw off the input match. Obviously the amp input is
designed
to be matched to tubes that are new. The amp has plenty of head room and
a
marginal tube can still let the amp make 1500 watts yet "may" present a
input imbalance. NOT to be overlooked. As someone who does extensive
amplifier repairs of most tube amps, I always have "known" good tubes of
all types to substitute into amps to eliminate tubes as being the
problem.
Prem, if a tube was bad the power output would be much lower than the
1500w
you measured.
-----Original Message-----
From: Gerald Williamson via Amps <amps@contesting.com>
To: va3uma <va3uma@gmail.com>; amps <amps@contesting.com>
Sent: Sun, Oct 19, 2014 9:21 am
Subject: Re: [Amps] Fwd: Ten-Tec Titan 425 - input SWR high
Prem, if a tube was bad the power output would be much lower than the
1500w
you measured.
The spectrum analyzer does not have enough drive power, same as the MFJ
Analyzer, to test input vswr.
The unchanged plate tune and load settings suggest the amplifier is
working
properly as well.
Happy hunting!
72,
Gerald K5GW
In a message dated 10/19/2014 8:37:44 A.M. Central Daylight Time,
va3uma@gmail.com writes:
Good morning gentlemen, and thanks to all for the quick and concise
replies.
- One of the tubes being bad: Will see if spares are available
- LPF caps going bad: My plan was to analyze the cut-off freq for each
band
(@ Z=50R) on my Spec-analyzer/tracking-gen - but left this option to the
last, and also wanted to hear of other 'easy' methods from the gurus
who've
already worked on this Amp.
- Plate/Load settings: The actual numbers match the ones in the manual
(surprisingly - even after all these years).
73,
Premwww.qsl.net/va3uma
---------- Forwarded message ----------
From: Prem <va3uma@gmail.com>
Date: Sun, Oct 19, 2014 at 9:24 AM
Subject: Re: [Amps] Ten-Tec Titan 425 - input SWR high
To: wl7e@arrl.net
Roger that, Joe. Will let you know.
73,
Prem.
On Sun, Oct 19, 2014 at 9:12 AM, Joe <wl7e@arrl.net> wrote:
> Prem,
>
> I would be interested in what you find out. I am having the same
> trouble.
> I am now replacing the tubes in my Alpha as that seems to be the
culprit.
>
> 73,
> Joe WL7E
>
> On Sun, Oct 19, 2014 at 5:02 AM, Prem <va3uma@gmail.com> wrote:
>
>> Friends, for a long time now, the input SWR on my friend's Ten-Tec
Titan
>> 425 is very high (average > 2 on all bands) - when measured with a
>> MFJ
>> analyzer at the input - with a 50R dummy-load at the AMP output.
>>
>> So long, he's used an ATU between the exciter and the 425, but I'd
>> like
to
>> find out if there's way to fix this SWR problem (no slug-tuning.
>> fixed L
>> and C in the i/p LPF).
>>
>> I've already checked/assessed the following:
>> 1- Amp gives full o/p of 1500W pep on a DL with an ATU between the
exciter
>> and the amp (so, tubes should be OK ?)
>> 2 - The vacuum relay contacts test 100% OK with a multi-meter
>> continuity
>> test.
>> 3 - No visual or smell indication of any burns/arcing/toast - in the
>> I/P
>> LPF or in any other circuit elements.
>> 4 - Band switch contacts look good. Cleaned with De-Oxit - just to be
>> on
>> the safer side.
>> 5 - Ig and Ip are as per specs
>>
>> Any help/lead is appreciated.
>>
>> 73,
>> Prem
>> VA3UMA
>> www.qsl.net/va3uma
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
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