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Author Topic: SB 200 80 Meter dilemma  (Read 730 times)
KA7LPO
Member

Posts: 3




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« on: February 27, 2004, 01:36:45 AM »

I own a SB 200 that operates fine on 40-10 meters. My tubes are worn. But on 80 meters the amp produces no more than 150-200 watts, with normal plate current and very low grid current readings. As well, while the exciter is keyed down, the power level will immediately drift down from 150-200 to 100 watts. Advise on places to begin to correct this problem? Bad caps in the 80 meter rf circuit? Bad tubes?

Thank you for any assistance,
Don
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W9GB
Member

Posts: 2656




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« Reply #1 on: February 27, 2004, 12:06:34 PM »

Don -

Here are the standard SB-200 references that you should check.

http://lists.contesting.com/archives/html/Amps/2003-03/msg00850.html

http://home.gci.net/~rnorgard/ampnotes.html

http://dayton.akorn.net/pipermail/amps/2003-September/036040.html

http://paq.net/Heathkit/SB220-200Parts.htm

http://lists.contesting.com/archives/html/Amps/2000-03/msg00556.html


W9GB
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M0BCG
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Posts: 40




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« Reply #2 on: March 14, 2004, 09:52:47 AM »

firstly check the connections at the input tuning coil and capacitors on the rear panel .

 second check the alignment of the bandswitches .

 third check the main output bandswitch inside the rf deck and make sure the contacts are ok or whether one side of them has burned out .

next make sure the 500pf additional capacitor is fitted in the right hand side of rf deck and that it is making a circuit from capacitor to bandswitch contacts .

to check for misaligned bandswitches just wiggle the bandswitch knob about and see if the 80m section comes to life when youre trying to get 80m working .

these amps have a rod running from rear to front of amp thru both bandswitches and heavy handed band changing over a period of years can make the wafer switches misaligned enough so that one or more bands may not have both sets of contacts connecting properly.

there are ferrite slugs inside each input coil for adjustment but normally these dont require adjustment .
i think most ferrite slugs in the input coils are screwed mainly all way in so they are only lined up with start of the input coil form .

have you checked both ends of the 80m band , ie 3.5mhz and 3.780mhz and seen what output you get, it does vary a little .

you should perhaps see well over 800w out on 80m under normal condx .

one other thing , just check that the amp hasnt been converted to another freq on the 80m setting , ie 6m or 160m , these amps are favourites to convert one band to 6m coverage  and it has been known for some to have 160m modification .
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