SV: SV: [AMPS] " Kein Rauch ohne Feuer ...."
measures
2@vc.net
Sun, 25 Jun 2000 06:40:46 -0700
>Rich you did not understand my worries abt the switch: It is the rf current
>I am worried abt. Tiny contacts that must handle ampereres of current. Is
>there any overload capacity when mistuning?
The greatest circulating current in the tank occurs when it tuned
correctly. When the tank is mistuned, circulating current decreases. To
handle the c. 8a of RF current, Heath used two, paralleled 15A-rated
contacts and forced air cooling. The result is bandswitch contacts that
run at low temperatures. The most common danger to the 220 bandswitch is
open contact arcing, caused by intermittent osc. at 110MHz.
>
>The 80 meter coil in the SB 220 is really soft even if the wire can handle
>the rf current.
There is not much heating in the SB-220's 80m coil. The air-flow
velocity is substantial.
> How many amps have been designed with weak 80 and 160 meter
>coils near metal walls just to show to the customer as much QRO as possible
>in as small as possible box? How many watts are lost in amps with low
>effiency? Would be nice if someone with an infrared camera could peep inside
> a number of amps and see where the power is lost?
Good idea. My guess is that there is typically high tank loss on 10m.
The good news is that when 10m is open, it really doesn't matter.
>
>I am sure many disc capacitors are overloaded and I really am worried about
>those dic capacitors used as coupling capacitors from anode to pi or pi/L
>output networks.
€ a good design uses one RF current-rated DC blocking C. When two caps
are paralleled for DC blocking service, they create an additional tuned
circuit that can cause problems.
> A potent danger to the outside world if the antenna isnt
>shorted from the DC point of view or if the RFC at the output fails.
>
€ Arcing air variable capacitors act to limit voltage like a zener.
With the typical 3000v supply and 1000v Load C, there is no danger if a
DC blocking cap shorts. The load Cap simply arcs to ground until the
circuit breakers in the primary of the HV transformer open. Arcs
typically have no more than 30v across them. I have never seen a DC
blocking capacitor short. Pick a proper capacitor in the first place
and it should last. .
>Guess I am spoiled having seen so many commercial Swedish Standard Radio
>ship transmitters in the past . .....
Swedish engineering is typically excellent. My sister-in-law is from
Thailand. She says that Volvos are popular there because they can handle
the terrible roads.
cheers, Hans
>----------
>>Från: measures <2@vc.net>
>>Till: <RMcGraw@blomand.net>
>>Kopia: "sm5ki" <sm5ki@algonet.se>, "Steve Thompson" <rfamps@ic24.net>,
>"AMPS" <amps@contesting.com>
>>Ämne: Re: SV: [AMPS] " Kein Rauch ohne Feuer ...."
>>Datum: lör 24 jun 2000 18.20
>>
>
>>
>>>It seems that Hans knows how to keep an amp alive. My SB-220 lived for
>>>years and years with no problems. Keem 'em cool is the secret to long
>>>life for all parts.
>>>
>>However, if your tubes happen to have above average VHF amplification,
>>the SB-220 can occasionally oscillate at c. 110MHz. Lower VHF Q
>>suppressors and glitch protection helps.
>>
>>cheers, Bob
>>
>>>measures wrote:
>>>>
>>>> >
>>>> >The funny thing is that overloaded components sometimes last much longer
>>>> >than theory says. Look at the old SB 220: that tiny receiving type
switch
>>in
>>>> >the output circuitry!
>>>>
>>>> The measured breakdown V in the SB-220 bandswitch is c. 5000V.
>>>>
>>>> > Very very soft as compared to commercial switches.
>>>> >That very weak 80 meter coil!
>>>>
>>>> It is #14 gauge copper with forced air cooling
>>>>
>>>> >My ex amplifier ( the very first in Sweden
>>>> >buit by me in 1968 -69? ) has never failed and is still in use up there
>>>> >above the Arctic circle with its original 3-500Zs with graphite anodes.
>>>> >Amazing. I always said, that one has to forget whats inside the SB 220
and
>>>> >look at the performance instead.
>>>>
>>>> Take a look inside and you will find forced air cooling on the tank and
>>>> the filament pins. This is good.
>>>>
>>>> > A very fb buy at a used price only a little
>>>> >bit higher than a pair of new 3-500ZGs made in France ( same as the
>>original
>>>> >tubes - the only difference is that little glass plate that lifts up the
>>>> >tube from the socket - less tendency for bad soldered pins to produce bad
>>>> >contact ).
>>>>
>>>> ''Bad solder'' results from the SB-220 cooling fan motor not turning
>>>> freely due to lack of lubrication. . Oiling the fan bearings every
>>>> couple of years will prevent this problem. . In older units without oil
>>>> holes, drill c. #55 oil holes above the motor shaft. Use a syringe for
>>>> oiling.
>>>> >
>>>> cheers, Hans
>>>> >----------
>>>> >>Från: "Steve Thompson" <rfamps@ic24.net>
>>>> >>Till: <amps@contesting.com>
>>>> >>Ämne: Re: [AMPS] " Kein Rauch ohne Feuer ...."
>>>> >>Datum: lör 24 jun 2000 07.17
>>>> >>
>>>> >
>>>> >>
>>>> >>
>>>> >>-----Original Message-----
>>>> >>From: N6BUU@aol.com <N6BUU@aol.com>
>>>> >>To: 2@vc.net <2@vc.net>; philk5pc@tyler.net <philk5pc@tyler.net>;
>>>> >>sm5ki@algonet.se <sm5ki@algonet.se>; n6er@yahoo.com <n6er@yahoo.com>;
>>>> >>amps@contesting.com <amps@contesting.com>
>>>> >>Date: 23 June 2000 19:59
>>>> >>Subject: Re: [AMPS] " Kein Rauch ohne Feuer ...."
>>>> >>
>>>> >>
>>>> >>>
>>>> >>>In a message dated 06/23/2000 11:22:32 AM Pacific Daylight Time,
2@vcnet
>>>> >>>writes:
>>>> >>>
>>>> >>><<
>>>> >>> As long as the hv ps filter capacitors make it through the one-year
>>>> >>> warranty period, all is well.
>>>> >>>
>>>> >>> - Rich..., 805.386.3734, www.vcnet.com/measures.
>>>> >>> end
>>>> >>> >>
>>>> >>>ok rich i guess i asked for that one! i just expect "parts" to last
>>>> >>>somewhat longer, than the warrenty period.
>>>> >>> HANK
>>>> >>>
>>>> >>Treated reasonably they do this, nearly all the time. I'm sure we would
>>>have
>>>> >>heard about it here if any amp brand had a tendency to fry its PSU in
less
>>>> >>than a few years. In truth, the reliability of raw components these
days
>>is
>>>> >>excellent.
>>>> >>
>>>> >>Is there any history that amps with 'insufficient' decoupling suffer
early
>>>> >>failure purely as a result of use on the lower bands? Is there any
>>evidence
>>>> >>that rf hurts electrolytic capacitors?
>>>> >>
>>>> >>Steve
>>>> >>
>>>> >>
>>>> >>--
>>>> >>FAQ on WWW: http://www.contesting.com/FAQ/amps
>>>> >>Submissions: amps@contesting.com
>>>> >>Administrative requests: amps-REQUEST@contesting.com
>>>> >>Problems: owner-amps@contesting.com
>>>> >>
>>>> >>
>>>> >
>>>> >--
>>>> >FAQ on WWW: http://www.contesting.com/FAQ/amps
>>>> >Submissions: amps@contesting.com
>>>> >Administrative requests: amps-REQUEST@contesting.com
>>>> >Problems: owner-amps@contesting.com
>>>> >
>>>> >
>>>>
>>>> - Rich..., 805.386.3734, www.vcnet.com/measures.
>>>> end
>>>>
>>>> --
>>>> FAQ on WWW: http://www.contesting.com/FAQ/amps
>>>> Submissions: amps@contesting.com
>>>> Administrative requests: amps-REQUEST@contesting.com
>>>> Problems: owner-amps@contesting.com
>>>
>>>
>>>
>>
>>
>>- Rich..., 805.386.3734, www.vcnet.com/measures.
>>end
>>
>>
>>--
>>FAQ on WWW: http://www.contesting.com/FAQ/amps
>>Submissions: amps@contesting.com
>>Administrative requests: amps-REQUEST@contesting.com
>>Problems: owner-amps@contesting.com
>>
>>
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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