What's wrong with running 3-500Zs "cherry red?" I think that's a fairly
natural color for them; they cool by emission, mostly, and "red" is a pretty
normal color.
Bright orange/yellow is hotter, and I've run 3-500Zs at that color temperature
lots of times. My last set lasted 22 years, operated like that almost every
day.
WB2WIK/6
________________________________
From: amps-bounces@contesting.com on behalf of Roger
Sent: Sun 7/12/2009 5:02 PM
To: n1miw@cox.net
Cc: Amps@contesting.com
Subject: Re: [Amps] Tube choice for SB-200 on 6 meters
Larry wrote:
> I agree with you as well Carl. When I use my existing SB-200 on digital,
> I will tune for max output (70 watts max on the input), then drop the power
> down to 350-400 by reducing drive. I just wish they made the amplifiers
> where you can easily see the tubes so they don't turn a cherry-red while
> tuning.
I used to *run* the 3-500s in my 2K4 that way. Never had one fail. That
was with about 1200 out. The original transformer had been replaced
with a Peter Dahal, but I don't know why if spending that much the
original owner didn't push the voltage up a tad.
73
Roger (K8RI)
> As I'm tuning, I always look into the amp to make sure everything's
> OK inside, as well as watching the grid and plate current. I had enough
> trouble getting this amp to work properly on 15 & 10 that I don't need to
> damage it again by a preventable mistake. That's what I bought this other
> 200 for :-). ...Larry
>
> PS Oh, something else that I do is refer to my "cheat sheet" when making
> large freq. changes so I can keep the tune-up time to a minimum & not abuse
> the radio and amp.
>
>
>
> -----Original Message-----
> From: Carl [mailto:km1h@jeremy.mv.com]
> Sent: Saturday, July 11, 2009 3:34 PM
> To: David Craig; n1miw@cox.net; Amps@contesting.com
> Subject: Re: [Amps] Tube choice for SB-200 on 6 meters
>
>
> As designed in the 60's its a 1 KW INPUT amp with roughly 600W expected
> output.
>
> Original somewhat leaky filter caps and their equalizing resistors put extra
> load on the transformer.
>
> Harbach sells a new fan with a higher speed motor and a new PS board kit
> thats a bargain.
>
> Once a properly converted amp is tuned up at 50.2 there is no need to touch
> it again when operating 50.0 to 50.4 unless tubes or antenna are changed.
> Some people take forever to tune and are always messing with it. WRONG!
>
> Ive run a 200 for a typical weekend in contests or 3-5 hours straight on CW
> during DX openings at 700W out. For digi modes keep it down around 450-500W
> and give it a break once in awhile. Reduce power ONLY by reducing drive;
> dont mess with the Load control.
>
> Its no different than running most amps in digi modes at full bore on HF;
> some just wont take it. And that includes some Alpha's.
>
> Over the decades Ive noticed that most hams dont know how to tune and use
> any amp.
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: "David Craig" <davidhcraig@verizon.net>
> To: <n1miw@cox.net>; <Amps@contesting.com>
> Sent: Saturday, July 11, 2009 12:42 PM
> Subject: Re: [Amps] Tube choice for SB-200 on 6 meters
>
>
>
>> I'll defer to the comments of others on the 572b insofar as stability
>> at
>> 50 MHz is concerned. One thing however is a virtual certainty- 572b
>> conversions (at least SB200s) do not hold up with hard duty-cycle use such
>> as digimodes or contest-style operating at 50 MHz. Be it the inadequate
>> PS,
>> the tubes, or whatever, regardles of the style of monoband conversion it
>> needs to be treated with kid gloves. If it is all you can do, then I'd
>> say
>> go for it as it is better than nothing, but don't hit it too hard. 73
>> N3DB
>>
>>
>> ----- Original Message -----
>> From: "Larry" <n1miw@cox.net>
>> To: "'Carl'" <km1h@jeremy.mv.com>; <Amps@contesting.com>
>> Sent: Saturday, July 11, 2009 10:59 AM
>> Subject: Re: [Amps] Tube choice for SB-200 on 6 meters
>>
>>
>>
>>> The problem I have is that I do not know what I am doing with these tubes
>>> for this conversion. I have yet to come across a conversion that
>>> everybody
>>> agrees with. I don't want to be a "hack", I just want to get an amplifier
>>> on
>>> the air for 6 meters, do it myself, and not spend an arm & a leg getting
>>> it
>>> there. The amp I have was purchased for the right price - I wish it was
>>> the
>>> 220 that I had, because of the tubes. However, since I don't, unless
>>> someone
>>> can tell me how to do the conversion SAFELY, I would just prefer to
>>> change
>>> the tubes to ones that are rated OK at 50MHZ. Larry N1MIW
>>>
>>> -----Original Message-----
>>> From: Carl [mailto:km1h@jeremy.mv.com]
>>> Sent: Saturday, July 11, 2009 9:26 AM
>>> To: n1miw@cox.net; Amps@contesting.com
>>> Subject: Re: [Amps] Tube choice for SB-200 on 6 meters
>>>
>>>
>>> Obviously I do not want to use the 572B's because of the controversy
>>> surrounding them at this frequency. TIA... Larry N1MIW
>>>
>>>
>>> There is no controversy among those that know what that are doing. Only
>>> the
>>> hacks blow them up and then send the amp to me or others to be done
>>> right.
>>>
>>> Carl
>>> KM1H
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: "Larry" <n1miw@cox.net>
>>> To: <Amps@contesting.com>
>>> Sent: Saturday, July 11, 2009 12:34 AM
>>> Subject: [Amps] Tube choice for SB-200 on 6 meters
>>>
>>>
>>>
>>>> Hello group,
>>>>
>>>> I'm looking for some information on converting an SB-200 to 6 meters.
>>>> I
>>>> originally thought about using the Russian GI-7B tube, but now I'm not
>>>> sure.
>>>> It looks like I can only use one tube due to power supply limitations.
>>>> What
>>>> have you guys seen in real-world conditions if you used this tube? Will
>>>> I
>>>> see about 500 CLEAN watts out from the single GI-7b (someone said in the
>>>> archives that one of these tubes equals 2 572B's)? Can I use 2 GI-7b's
>>>> without letting the smoke out of the transformer or PS? There's also the
>>>> mod
>>>> for the GLA-1000 where the output watts is ~750 which I'm using for
>>>> comparison, but I don't know what the current was at that limit. The
>>>> spec
>>>> sheet for the GI-7b might put the current for 2 tubes at close to 1A,
>>>> which
>>>> the SB-200 can't supply as far as I know.
>>>>
>>>> If the single or dual GI-7b can't give me 500 watts+ out from the
>>>> SB-200
>>>> PS, is there another tube (or tubes) of choice you would recommend for
>>>> the
>>>> SB-200? Obviously I do not want to use the 572B's because of the
>>>> controversy
>>>> surrounding them at this frequency. TIA... Larry N1MIW
>>>>
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>> _______________________________________________
>>> Amps mailing list
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>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
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