There's others beside Astron that float the neg terminal from chassis.
73
Bob, K4TAX
----- Original Message -----
From: "Mike Hyder -N4NT-" <n4nt_m_o_hyder@charter.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Monday, November 28, 2005 7:30 PM
Subject: Re: [TenTec] Comments on "Repairs"
> Larry, when you ask for suggestions, I respectfully suggest you not
> dismiss
> them out of hand.
>
> Robert K4TAX said, ">Is the power supply negative connected to chassis of
> the power supply? Some
>>power supplies {name with held} float the negative and are prone to RF
>>getting into the voltage sense circuit and allowing an oscillation to take
>>place in the supply. Can spell trouble for the radio.
>
> The offending power supplies are Astron RS-35 I don't withhold names.
>
> 73, Mike N4NT
>
> ----- Original Message -----
> From: "Larry DiGioia" <listacct@longwire.com>
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Sent: Monday, November 28, 2005 7:42 PM
> Subject: Re: [TenTec] Comments on "Repairs"
>
>
> Since you guys were kind enough to give me multiple replies, I am going
> to reply to all messages at once:
>
> Robert & Linda McGraw K4TAX wrote:
>
>>Here goes........have patience with my probing.
>>
>>What type of power supply you using?
>>
> Astron RM-35M rack mount set to exactly 13.8VDC per another long-time
> Omni owner.
>
>>Is the power supply negative connected to the chassis of the Omni via a
>>separate ground and not just the negative power lead? It should be.
>>
>>
> Not exactly, but both are connected to a 2" copper ground bus bar using
> 1" braid, only 2 to 3 feet.
>
>>Is the power supply negative connected to chassis of the power supply?
>>Some
>>power supplies {name with held} float the negative and are prone to RF
>>getting into the voltage sense circuit and allowing an oscillation to take
>>place in the supply. Can spell trouble for the radio.
>>
>>
> Well, I just ran all weekend with my standby Yaesu radio connected to
> the same PS. This is also the same PS, set up the same way, that I have
> been running since 1998.
>
>>Are all pieces of station equipment connected together back to a common
>>point such as the power supply via separate dedicated ground cables.
>>Should be.
>>
>>
> All equipment goes (via copper braid or copper strap) to the bus bar,
> which is connected via copper strap to a ground rod just outside.
> Maximum distance between equipment is maybe 4 feet.
>
>>Regarding the tuner, do you use the radio to adjust the match or do you
>>have
>>a bridge like and Autec or MFJ to set the match?
>>
>>
> {The best antenna tuner that money can buy, used incorrectly, is no
> better than a cheap tuner.}
>
> The tuners are a Nye Viking and a Palstar BT1500. I use my MFJ tester to
> determine whether operation is even possible on bands/antennas, then
> tune up again with the radios at 5 watts or so and gradually increase
> power. I made a table of all possible bands/settings which I keep on the
> wall, and use as a starting point. When it's time to switch bands, I
> gradually inch up the power as before, but all that's usually needed are
> minor touch-ups.
>
>>Is the meter used to measure SWR in the tuner, or an external meter, or
>>the
>>one in the radio. Coax cables between the devices can cause the SWR to
>>look
>>good at one place and produce a very poor match at another location in the
>>system. This can be due to a bad cable or poor connector installation or
>>loose connector on the SO-239.
>>
>>
> I used a Drake external meter for the first 5 years or so with my
> home-made tuners, then after switching to the two commercial ones, I use
> their internals. There are a few coax switches, though... there are a
> couple of 3-foot and a couple of 6-foot "jumpers" altogether, all
> commercially-made RG213.
>
>>In my case I use a 238 tuner with its internal SWR/Power meter, a Daiwa
>>CN-801 SWR & Power meter, and the SWR meter in the radio. In adjusting
>>the
>>tuner I switch in and use an MFJ antenna bridge. Then switch the radio
>>into
>>the system. In all cases, with power, all three SWR indicating devices
>>will
>>show the same and correct SWR reading. I have seen installations where
>>SWR
>>at 3 places will be different. This indicates circulating RF and that can
>>give false SWR indications. Hope you don't have this condition.
>>
>>
> Well, with two balanced lines leading into the shack, "circulating RF"
> is pretty normal here. But also note, that the last two times this radio
> gave out, it was while advancing the power on 20m (coincidence?) and I
> barely made it past 10 watts or so when it blew. Once into my Hy-Tower
> and another time into a (balanced) dipole.
>
>>Parts for the Omni VI and VI Plus are basically "off the shelf" parts. Be
>>assured that Tentec Service is fixing the radio, taking it through a 24 hr
>>burn-in and it is working when it gets to you. Hate to say it, but
>>something in your station or your method of tune-up is causing a problem.
>>
> I won't argue that. For a while I thought it was a cheapo coaxial
> lightning arrestor (the arc-plug type.) Then I went to having all
> suppression outside the house, via Polyphaser for coax and Wireman
> spark-plug gadgets for the balanced ones.
>
> I'm with you on the PS issues, but will wait to hear more. Thanks!
>
> Jeff Frank wrote:
>
>>I had a problem with my Omni Six where the radio had to be returned to
>>TenTec four times and each time something else would go wrong. Eventually,
>>the radio was fixed and the folks at Tentec remained as helpful as they
>>could be. After the first two times TenTec paid all the shipping and
>>didn't
>>charge me for their work.
>>
> Same here! I do appreciate it, and I know they are trying.
>
>> In my experience they will do the right thing. Don't give up.
>>
> Thanks for the encouragement! Well, it's kind of self-evident here on
> the list: a half-dozen guys who had similar problems, and they are all
> still Ten-Tec owners, if not evangelists...
>
> Denton wrote:
>
>> Larry, the same thing happend to my Omni VI.....went back 3 times to
>> have both the finals and final driver transistors replaced.
>
> I am pretty sure they never replaced the actual finals, it has always
> been smaller components.
>
>> In my case, I was running the rig and another hf rig at the same time
>> on a common power supply...on different bands and different antennas.
>
> Not here, although I have a spare rig now, I have never transmitted on
> both at the same time.
>
>> Right now, I am running separate power supplies, Ten Tec model 961,
>> one per hf rig....otherwise same antenna tuners and same antennas as
>> before. So far, fingers crossed.
>> I will never be too sure what caused the finals to blow...but I think
>> that rf was getting into the final brick via the power supply positive
>> lead.
>
> Well, I would be willing to switch power supplies if I thought it would
> cure it, but remember, the same one ran it for 5 years with no problem.
> Based on what I am hearing, I think I will stock up on more ferrite cord
> clamps... but there is already one on the supply lead just outside the
> radio.
>
>>Those are the classic symptoms of a parasitic oscillation. You probably
>>already know this. But in any case, you need to look at suppression and
>>low
>>pass (HF) filters in the rest of the path to see if you can break up the
>>oscillation.
>>
>>73 de Gary, AA2IZ
>>
> Yes, I agree, but as to the cause, I am lost. I had a low-pass filter
> for TVI purposes previously, took it out a while back because we went to
> satellite, hmmm, timing is right... thanks.
>
>> Larry....do you notice the same behavior while transmitting into a
>> good dummy load or does the problem surface only when transmitting
>> thru your tuner into your antenna???
>>
>> 73, Joe W2KJ
>
> Well, first, I don't own a dummy load, I think they are useful for
> tuning "tuneable" transmitters, but on a solid-state final, I don't see
> it. As for "the problem surfacing," when it does, I am dead in the water
> and the rig goes back to Tennessee, last time it was dimming the lights
> on transmit...
>
>>Your PA is drawing too much current for whatever reason. Use a TT 961 PS
>>to
>>protect the PA or put a similar "fast cycle" 22 Amp breaker in line.
>>
>>I've been running either an Omni D, Paragon II, Corsair II, or OMNI VI+
>>for over 25 years. I always used a matching TT power supply and never had
>>a PA problem although the PS circuit breaker "popped" many times when I
>>made a mistake on tune up.
>>
> This really fits. My present PS is way over-rated at 35A, so I am going
> to seriously consider this. Thanks!
>
> Lyle Dunlap wrote:
>
>>Your getting some good advice Gary I would just add a couple of things.
>>Get
>>a 20 AMP Air Pax ckt bkr. years ago one could get them from TT but maybe
>>not
>>today.
>>
>>
> I would love to find one, I will keep this in mind if I don't go with
> the 961.
>
>>Another thing if you do not use some device such as an ant. analyzer then
>>at
>>least tune up on a duty cycle. IE: a keyer on fast dits, if nothing else.
>>I hear a lot of steady key down tuning these days, even tubes dont like
>>that.
>>
>>
> I already made a resolution to do this after getting the new tuners. The
> Nye will not tolerate it, the metering is very strange, it has some kind
> of a delay in it.
>
>>That fast acting ckt bkr will keep you out of trouble even if you dont
>>know
>>what your doing. Not to imply you dont.
>>
> No offense taken. When chasing DX I sometimes get emotional and
> heavy-handed. I also should mention that I run PSK. When I can. But I
> was always remembering the ads for the Omni, talking about how the final
> would "automatically fold back the power when necessary," and for years,
> it did.
>
>>I've had similar experiences (current jumping up all of a sudden because
>>of
>>self-oscillation) with the older Ten-Tec radios. In my case the trouble
>>was
>>caused by the rig's not producing ALC voltage because of bad diodes. I
>>called Garland and he said something like, "Yep, they can do that if the
>>diodes are bad." It cost me about $0.96 to make the repair.
>>
>>73, Mike N4NT
>>
> That's what they replaced last time. But for me, when it happens, it
> self-destructs and never "comes back."
>
>
>
> --
> Larry N8KU
>
> w w w . l o n g w i r e . c o m
> 100% CW 100% HF
>
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