If the soft start relay fails to close, then the resistor will burn up,
because it is only rated to handle the full load for a short period of
time. So you should investigate why the relay stayed open.
73,
Victor, 4X6GP
Rehovot, Israel
formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 04/10/2024 3:11, Larry Carpenter wrote:
Hi Folks,
Its been a while since I posted anything but I do enjoy
reading messages on this group. I find them very helpful. I just recently
acquired an SB-220 with all the Harbach mods, soft start, soft key, metering
board and power supply board with new caps and bleeders. I used this amp for a
couple of days and it worked fine with 3000 VDC in the SSB position with about
1100 watts out and about 2250 VDC in the CW position. While sitting in a idle
state there was a flash and it immediately lost power. After some investigation
I found one of the wire wound ceramic resistors (20 ohm @ 10 watts) had opened
up and left a black zorch on the soft key board. It also appears that one post
of the 48VDC K2 relay got really hot. It looks like these resistors will be
easy enough to replace but I am concerned at what caused the resistor to open
up. I am wondering If I should replace the resistors and take the tubes out
before powering on and see what happens. Neither of the circuit bre
ake
rs on the back of the amp had tripped. Just wondering if anyone else had run
into this problem with Harbach Soft Start module. Any advice greatly
appreciated.
Larry Carpenter
AA4VI
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