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Author Topic: sb200 voltage  (Read 687 times)
VE1CZ
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Posts: 70




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« on: September 26, 2004, 11:48:29 AM »

I have a near mint condx sb200 amp, this amp was showing about 2100 volts on the meter when i got it a short time ago, now it only shows 1700 volts but the output power hasn,t changed at all?? any ideas?
              Tnx Bob ve1cz
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K7KBN
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Posts: 2785




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« Reply #1 on: September 26, 2004, 04:41:33 PM »

Could be a sticky or slow meter movement, or maybe some "static cling" on the meter face.  Try this:

Get one drop of dishwashing soap on your finger, and rub it all over the meter face, including onto the metallic front panel.  When it's dry, take a very slightly damp cloth and remove most of the soap, leaving some around the edges.  This will "shunt" static charges off the meter, and might be your cure.  Sounds silly, I know, but it does work.
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73
Pat K7KBN
CWO4 USNR Ret.
AD4U
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Posts: 2157




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« Reply #2 on: October 06, 2004, 10:25:43 AM »

Check the value of the high voltage dropping resistors that enable the panel meter to read the plate voltage.  I think there are 3 ea 4.7 Meg resistors that drop the high voltage, but I am not sure because I am at work and my SB 200 manual is at home.  I have repaired several SB 200's that these resistors increased in value due to heat and consequently made the high voltage appear to be low on the panel meter.  If this is the problem, I suggest you use higher wattage resistors than the originals.  Also might be good to use more resistors that would result in a lower voltage drop across each.  Just make sure the total resistance is the same as the originals.

Dick  AD4U
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M0BCG
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Posts: 40




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« Reply #3 on: October 21, 2004, 12:49:23 PM »

wiggle the HV ,PWR PLATE SWR  switch around  on the HV setting  , youll probably see the voltage reading change .

 the last sb200 i looked at  did this .

if youve had the rf deck out of its case then check that none of the switch tags have bent and are touching the chassis .

the location of that switch is very close to chassis and it is easy for it to get moved about when you remove rf deck from the case .

transformer output voltage is 800v ac .

if you have a high voltage probe you can measure the anode voltage directly at anodes as its allways got HT on the anodes in that amp .

usuall high voltage reading is between 2100-2400v depending on mains voltage locally .

 
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K0IYA
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Posts: 22




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« Reply #4 on: August 22, 2006, 11:18:15 PM »

Same with my Sb200. I use to show about 2300Hv now 1900. I just put in a Harbach power module, the original was showing wear. But, the HV is still 1900. I have new tubes coming because only one good one getting about 300 watts, but not using it until the tubes come. Will that help the HV. Does that dish soap thing really work?  Any other ideas? Rob
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KD5PNT
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Posts: 1




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« Reply #5 on: May 26, 2009, 12:34:09 PM »

yes the diswashing soap does work . also , although I have never tried it an anti static dryer sheet should also work .
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KA5N
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Posts: 4380




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« Reply #6 on: May 26, 2009, 03:55:38 PM »

If you don't have a high voltage probe, you can measure the voltage across each electrolytic cap in the power supply, add the voltages and the sum is the high voltage for the tube plates.  Should be around 2400 volts.  Be CAREFUL lethal voltages!!!
Allen
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