[Heathkit] SB-200 Help

Fri Aug 10 03:47:16 EDT 2007

It gives me grief on every band except for 40m for some reason, on 40 i can 
run full output of 100w on the 847 and get full power out of the amp.  But 
when i go to 10, 15, 20, 80, then i get HI SWR on the 847 and i can't drive 
the amp.

I tried your suggestion, was just about to say the heck with it and go to 
bed and leave it for another day.  I put the radio in AM mode on 80m, put a 
dummy load on the amp and tried adjusting it for max output.  That works ok, 
but only if i stay under 20w, anything above 20w and the 847 folds back and 
indicates a HI SWR once again.  I can tune across the entire band as long as 
i stay under 20w it doesn't present a high swr to the radio, if i go above 
20w then the entire band presents a hi swr again.  So i can't find any place 
on the band where it will take full power!

I have been trying to find info in the manual and on the web with no 
success.. How do you adjust the input coils on the SB-200 and what should i 
look for regarding the flaky meter shunts that you mentioned?

As for the previous owner, he was using the exact same radio, FT-847, which 
was a bit of a selling point seeing how well it worked for him.  I hauled it 
home and got the exact opposite.  The only difference is he was using an 
external keying interface and i built in the SK-201, well a home brew 
version of that circuit, to use with my radio.  That works perfectly, just 
the SWR problem to deal with now.

73,

Scott

----- Original Message ----- 
From: "Peter Markavage" <manualman at juno.com>
To: <heathkit at mailman.qth.net>
Sent: Friday, August 10, 2007 2:38 AM
Subject: Re: [Heathkit] SB-200 Help

> You didn't indicate what band you were operating on. Try to test it on a
> band like 20 or 40 meters where the max. is 300 to 350 Khz. It could be
> the SB-200 input coils for each band were tuned to at a certain point in
> each band, and it you're not testing anywhere near that point, the 847
> probably would see a high SWR. One of the problems when running a
> solid-state rig that is very sensitive to SWR beyond the manufacturer's
> normal range. You also didn't indicate what mode you were testing in.
>
> Try this; put the 847 in the AM mode, key down and then adjust the 847's
> output to about 10 to 15 watts. Put the SB-200 output on a dummy load.
> Since the SB-200 is a linear amplifier, don't screw with dip and load.
> Just tune the amplifier for maximum output either using the RF output
> meter position or an external meter between the dummy load and the
> SB-200. If you want, you could take a minimum of a 100 watt light bulb or
> higher wattage and connect that to the output of the SB-200 instead of
> dummy load. Note: don't try this in the key-down CW position or a
> modulated SSB position. You'll burn out the bulb. Again, for testing
> purposes and on a dummy load of some sort, and running the lower 847
> power on AM, you can sweep (tune) each band with the SB-200 connect to
> see if there's a dial range where the SWR is manageable. Once you've
> determined, that both rigs can work together on some range of frequencies
> but you can determine what, if any additional action you might want to
> take. i.e. automatic or manual tuner, if possible, between the 847 and
> SB-200, or readjusting the SB-200 input coils for your range of
> operation. There's lots of great info on the SB-200 on the web. Also,
> meter shunts in the SB-200 were known to get flaky after many years of
> operation.
>
> You also didn't mention what type of rig the previous owner used to drive
> the SB-200. I've driven my SB-200's with an Icom IC-706MKIIG, IC-706,
> IC-756PRO II, IC-7000, Kenwood T-5999D, Kenwood TS-830S, and tons of
> boatanchor rigs.
>
> Pete, wa2cwa
>
> On Thu, 9 Aug 2007 23:48:42 -0500 =?iso-8859-1?Q?KB=D8NLY?=
> <kb0nly at mchsi.com> writes:
>> Ok, i got my SB-200 hooked up and now i got more problems than i know
>> what to do with.
>>
>> Lets start from the top..
>>
>> I built and installed a SK-201 Soft Key module and that works great,
>> keys the relay no problem.
>>
>> I followed the manual and hooked it all up.
>>
>> And i went to the operating instructions, this is where everything
>> went FUBAR.
>>
>> It says to switch it on and put the meter switch on Plate and i
>> should see 90ma of idling plate current with no drive from the
>> exciter, i got ZERO.
>>
>> Than it says i should advance the drive level of the exciter for
>> 200ma of plate current.  Can't, why?  Because the amp is presenting
>> a 3:1 SWR to the radio and the FT-847 backs down the power output
>> because of the HI SWR condition it's seeing.
>>
>> If i flip the meter switch to the Rel Pwr position i can see the
>> power output of the 847 but thats about it.  I can adjust the tune
>> and load controls until i'm blue in the face and get nowhere.
>>
>> This amp was working perfectly before i bought it, and yes i am sure
>> of that, but now i can't get it to do diddly.
>>
>> 73,
>>
>> Scott
>>
>> _______________________________________________
>> List Administrator: Duane Fischer, W8DBF
>> ** For Assistance: dfischer at usol.com **
>> $$ See the vintage area on the HCI web site - http://www.w9wze.org
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> _______________________________________________
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> ** For Assistance: dfischer at usol.com **
> $$ See the vintage area on the HCI web site - http://www.w9wze.org $$
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