Pages: [1]   Go Down

Author Topic: SBE-34 low power?  (Read 156 times)

KG9H

  • Member
  • Posts: 121
    • homeURL
SBE-34 low power?
« on: December 31, 2021, 06:23:58 AM »

So I purchased an SB-34 and after repairing the issues with it that were incurred in shipping, I am getting lower than expected power out.  Voltages on final are 450 as expected.
Current is about what is expected but.... I get only about 26 watts out.  Changed out driver, then finals, still 26 watts out.
Anyone here see this before?
Logged

K1KP

  • Member
  • Posts: 144
Re: SBE-34 low power?
« Reply #1 on: December 31, 2021, 06:30:21 AM »

Do the load and plate controls behave as expected? Do you see a dip in plate current at resonance? Is it the same on all bands or only some?

The fact that voltage and current are as expected implies drive to the finals is good, and there's a problem in the output network.

More background data would be helpful in diagnosing...

-Tony, K1KP
Logged

KG9H

  • Member
  • Posts: 121
    • homeURL
Re: SBE-34 low power?
« Reply #2 on: December 31, 2021, 06:37:48 AM »

Yes both load and plate react as they should.  I dont think neutralization comes into play on 80 meters but indeed the dip corresponds to maximum power.  All bands are about 1/2 power from what I expect.  SSB and CW are both low.
« Last Edit: December 31, 2021, 06:42:29 AM by KG9H »
Logged

K1KP

  • Member
  • Posts: 144
Re: SBE-34 low power?
« Reply #3 on: December 31, 2021, 07:52:21 AM »

Check the bias and screen voltages too...
Logged

KG9H

  • Member
  • Posts: 121
    • homeURL
Re: SBE-34 low power?
« Reply #4 on: January 04, 2022, 07:19:05 PM »

So found the problem.  The 450VDC slumped in transmit down to 380 volts.  Replaced caps in DC line and I now get about 65 watts on 75.  Done  de KG9H (wonder what my next project will be??)
Logged
Pages: [1]   Go Up