A parasitic suppressor could be fried if the arcing is in the Tune cap or
bandswitch.
Carl
KM1H
----- Original Message -----
From: <k2dp@charter.net>
To: "Dan Atchison" <N3ND@aol.com>; <amps@contesting.com>; "Jim W7RY"
<w7ry@inbox.com>
Sent: Monday, June 20, 2011 10:57 PM
Subject: Re: [Amps] Centurion Problems - Arcing on 10, 15 and 20 mtrs
> Dan,
>
> I can sympathize with you. I have a Centurion which I purchased used in
> very
> good condition. Had it for a few years and poof went the HV xfmr while the
> unit was in standby. The amp was approximately 16 years old when the xfmr
> primary opened as you described. $550 later, I had a new TT replacement
> xfmr and we were back in business (but a bear to remove and replace). Now,
> 3
> years later, the amp is arcing on 20 mtrs into a dummy load. Have not
> checked it out yet, but put my trusty 40 year old SB-220 back on line
> (with
> original caps, etc) and will get around to the Centurion when time
> permits.
>
> Would be curious to know if anyone else has seen an arcing problem which
> immediately causes the Power Output to drop to zero. The problem does not
> seem to exist on 40/75 mtrs but is prevalent on 10, 15 and 20 into a Bird
> dummy load.
>
> 73 and good luck,
> Dave
> ----- Original Message -----
> From: "Dan Atchison" <N3ND@aol.com>
> To: <amps@contesting.com>; "Jim W7RY" <w7ry@inbox.com>
> Sent: Sunday, June 19, 2011 8:13 PM
> Subject: [Amps] Centurion
>
>
>> Well, interesting repair. Yes, the problem was a leaky Q1 on the
>> display board. Replaced with a non-descript 2N3904 since I didn't have
>> the 2N4124 that was bad. Schematic called for a different transistor
>> altogether.
>>
>> Delving into the circuit also revealed why I had no PTT. Seems if the
>> amp detects RF output prior to PTT, then the PTT circuit is disabled. I
>> had no RF output, but the leaky transistor had the same effect as
>> rectified RF allowing voltage where it was not wanted!
>>
>> Also found out the step-start circuit is fried. Read that as the power
>> resistor is fried. The board it's on is behind the HV transformer so I
>> may just leave it alone.
>>
>> I know many people have Centurions. This one is a 422B, the black (and
>> current) faced amp. I've had it almost eight years now and it's been a
>> problem child. Early on in its life I lost two HV transformers.
>> Tentec had a problem with these and never, NEVER admitted as such. One
>> was replaced under warranty, the next one lasted seven months. Both
>> failed with shorted primaries. After the second failed, I bit the
>> bullet and bought a Peter Dahl and never looked back. I had Dahl
>> slightly up the secondary voltage on this one.
>>
>> This is about the sixth repair on the unit, by far and away my least
>> reliable piece of equipment. Even the schematics are wrong -- and I
>> bought the amp after it had been on the market already for 15 years or
>> so. Even the board screened nomenclature was incorrect on a few boards
>> that I noticed while troubleshooting. I may never buy another piece of
>> Tentec gear again.
>> _______________________________________________
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>>
>
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