[Amps] SB-220's, 3-500's, some history

[Peter Voelpel]

Yes, something which did well at 100W AM (400W PEP) will do fine at 600-700W
PEP if the antenna is low SWR and the tank properly tuned.
The many toasted contacts clearly show its being on the edge.

73
Peter 

-----Original Message-----
From: Carl [mailto:km1h at jeremy.mv.com] 
Sent: Samstag, 7. Februar 2009 01:36
To: Peter Voelpel; 'Amps'
Subject: Re: [Amps] SB-220's, 3-500's, some history

Its the same construction as the AL-80 series and better than the AL-811
crap.

It was also used in many other 1000W CW input amps of the past. When the USA
went to a 1500W output the Centralab JV-9000 series came into use and is
what is most used today under an Electroswitch number.

Carl
KM1H


----- Original Message -----
From: "Peter Voelpel" <df3kv at t-online.de>
To: "'Amps'" <amps at contesting.com>
Sent: Friday, February 06, 2009 3:44 PM
Subject: Re: [Amps] SB-220's, 3-500's, some history


> The band switch of the SB-220 looks to me as one of a 100W transmitter 
> from
> the 60s.
>
> 73
> Peter
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] 
> On
> Behalf Of gudguyham at aol.com
> Sent: Freitag, 6. Februar 2009 20:51
> To: km1h at jeremy.mv.com; amps at contesting.com
> Subject: Re: [Amps] SB-220's, 3-500's, some history
>
> Carl et al, not an adervetisment by any means.? What prompted this 
> writing
> was the awareness of the insane prices that are being paid for Sb-220 
> amps
> particularly on EBAY for these amps that many can't say even work.? I 
> have
> heard horror stories about those paying high prices for even dead 
> amps.? I
> just wanted to enlighten the newbies who I feel are the ones pumping 
> up the
> price on them and don't know the pitfalls.? There "should" be more
> accountablity by the sellers of some of this junk, but you will notice 
> that
> most every amp on EBAY comes with a disclaimer and a "all sales final"
> slogan.? There was a time when a ham's "word" meant something, but not
> anymore.? EBAY is a dumping grounds.? So I figured if buyers knew the
> pitfalls etc, they might? be able to put the pressure on the sellers 
> to
> assure them that "at least" you might be getting an amp with a good
> bandswitch.? When you consider the odds that you agreed with me on, 
> there is
> good chance one will get a bummer amp.? Th  ey can look clean as a 
> whistle
> trust me, but that band switch could be toast.? Fortunately for US 
> Carl it
> doesn't matter too much.? I have had better luck on the other buying 
> venues
> where seller responsiblity is at a higher standard, but I have STILL 
> been
> burned there too.? I haven't seen as many Drake L4 amps, but I assure 
> you I
> have seen more than most, and I have never seen a bad band switch on 
> an L4,
> L4B.? For use an an HF amp, I would take an L4B over an Sb-220 any day
> especially in the used market.? You can almost bet the band switch 
> will be
> good on one of them, but I would not bet the same on the Sb-220.?
> Please....DON'T ask me why the band switch contacts go south, the pit 
> bulls
> have argued this point for decades, need I say more?? Suffice to say 
> these
> are the facts regardless of the causes.? Lou
>
>
> -----Original Message-----
> From: Carl <km1h at jeremy.mv.com>
> To: Gudguyham at aol.com; amps at contesting.com
> Sent: Fri, 6 Feb 2009 1:09 pm
> Subject: Re: [Amps] SB-220's, 3-500's, some history
>
>
> Nice advertisement Lou, business must be slow down there <G>?
> ?
> However with over 250 SB-220 family 6M conversions and many straight 
> repairs
> since the 60's I concur with 99% of the observations.?
> ?
> All the Amperex are graphite and I have a NIB pair of the Eimac 
> graphites in
> my tube collection as well as a pair of Russian prototype 3-600Z's 
> there
> were never released to market.....they didnt work very well.?
> ?
> Meanwhile, back to work, finishing up a LK-800A 6M conversion.?
> ?
> Stay warm, I see global warming has frozen another elderly homeowner.?
> ?
> Carl?
> KM1H?
> ?
> ----- Original Message ----- From: <Gudguyham at aol.com>?
> To: <amps at contesting.com>?
> Sent: Friday, February 06, 2009 8:33 AM?
> Subject: [Amps] SB-220's, 3-500's, some history?
> ?
>> Unlike many hams who could count on one hand how many SB-220 amps 
>> they >
> have?
>> owned in a life time, some have to go to their feet to keep score. > 
>> Well,
> I?
>> am now starting to count hairs on my head and thankfully I have not >
> experienced?
>> Alopecia quite yet. All kidding aside, I have had HUNDREDS of Sb-220 
>>  >
> amps?
>> though here on my bench in the last 12 years. I have also seen all > 
>> the
> sets?
>> of 3-500 tubes that were in them as well. Beginning with the SB-220,?
>> statistically the average used SB-220 has at least one burned or >
> vaporized band?
>> switch contact!! I would venture to say that 7 out of every 10 amps I 
>>  >
> have seen?
>> have a bad contact. That is pretty bad odds. If you are looking to > 
>> buy
> an?
>> SB-220 you should be real concerned about this!! Often times if the >
> contact?
>> is not vaporized that amp still works because the contacts are >
> redundant.?
>> Sometimes only one contact on one side is bad and on the other side > 
>> it
> is "OK".?
>> As soon as a high SWR is present or some mistuning, you'll here an > 
>> arc
> come?
>> from that contact. In the long run, if you use that band a lot, > 
>> failure
> is?
>> close by. Those are pretty bad odds. The problem is it is very hard > 
>> to
> see?
>> the contacts on the switch and the inside contact is almost > 
>> impossible?
>> without the use of a bright light and a dental type mirror. Most > 
>> other
> problems?
>> are simple to fix, but this problem is a bummer. Keep this in mind. > 
>> OK,
> now?
>> for the 3-500's. The Sb-220 has been around for a long time, most of 
>>  >
> them?
>> made around the time when we all used "load em up radio transmitters" 
>>  >
> most of?
>> them were capable of over 100 watts output, some Drake and Swan 
>> radios >
> put?
>> out 250 watts. Even the lower wattage radios did 160 to 180 watts >
> output.?
>> You could kill a pair of 3-500's with this kind of power input > 
>> levels.
> SO I?
>> have seen my share of weak tubes. As time went on and the usual > 
>> solid
> state?
>> 100 watt radio was the norm, you would be hard pressed to destroy a > 
>> pair
> of?
>> 3-500's with only 100 watts drive in an SB-220. So the odds of > 
>> getting a
> full?
>> output set of tubes in an Sb-220 is very high. I'd say in the 90 >
> percentile!!?
>> Well that's some good news. I have also seen many different types > 
>> of?
>> 3-500s. Eimacs, Amperex, and others, including the Chinese > 
>> varieties.
> Eimac in?
>> the early and late 60's made a run of graphite tubes, they looked >
> different?
>> inside, much like a Pagoda instead of the typical turbine fan blade. 
>>  >
> Amperex?
>> tubes all looked like this. Not sure if all were graphite or not, >
> however I?
>> have noticed in a small population of older tubes of this sort a >
> difference?
>> in bias requirements. Typically the standard 3-500 is self biased at 
>>  >
> about?
>> 2500 volts or less and no additional bias voltage is required to > 
>> lower
> the?
>> idle current to about the normal 180 to 200 mills. The Drake L4.L4B > 
>> had
> no?
>> additional bias voltage. The SB-220 with about 2900 volts on the > 
>> plates
> has?
>> about 5 volts of bias which settles the tubes down to about 180 
>> mills. >
> If you?
>> run the tubes beyond 3000 volts you will need 5+ volts of bias and as 
>>  >
> high as?
>> 13v as in the Ameritron AL-82. Interestingly however, there was > 
>> "some"
> and I?
>> have only seen very few old Eimac and Amperex 3-500 tubes that seem > 
>> to
> be?
>> self biased at 3000 volts and require no additional bias to lower the 
>>  >
> idle?
>> current to 180 to 200 mills. At first when I encounter these tubes, I 
>>  >
> thought?
>> they were bad since the idle current when biased at 5 volts is so 
>> low, >
> but in?
>> the long run they are full output. I've used several Chinese brand > 
>> tubes
> in?
>> the past and I have always been pleased with them. Their performance 
>>  > is
> right?
>> up there with the top brands. The Sb-220 itself had some evolution, >
> there?
>> were 2 different types of loading variable caps used, the Sb-221 used 
>>  > a
> wider?
>> spaced tune cap. The Sb-221 did not have 10 meters unless it was > 
>> built
> like?
>> anSB-220 in the beginning by the builder buying the "10 meter kit". > 
>> The?
>> Sb-221 as it is lacks a 10 meter contact on the band switch so it is 
>>  > no
> simple?
>> "mod" to make one work on 10 meters. You'll need an extra contact on 
>>  > the
> input?
>> switch as well and some input coils. They did due diligence on > 
>> keeping
> the?
>> CB'ers from using this amp easily!! Ditto for the later HL-2200 amp. 
>>  > It
> has?
>> been a rewarding experience for me to have done these hundreds of >
> autopsy's.?
>> I am getting to fell like the Dr. G. of Sb-220's. My morgue is ever?
>> expanding. 73 Lou W1QJ?
>> **************Stay up to date on the latest news - from sports scores 
>>  >
> to?
>> stocks and so much more. (http://aol.com?ncid=emlcntaolcom00000022)?
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>
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